Method forversatile content control

CROSS-REFERENCE TO RELATED APPLICATIONS

0001This application claims the benefit of U.S. Provisional Application No. 60/638,804, filed Dec. 21, 2004, entitled, “Memory System with Versatile Content Control.” This application is further related to U.S. patent application Ser. No. ______, [Docket 382US2], entitled, “Memory System with Versatile Content Control”; this application is further related to U.S. patent application Ser. No. ______ [Docket 382US3], entitled “Method Using Control Structure for Versatile Content Control”; this application is further related to U.S. patent application Ser. No. ______ [Docket 382US4], entitled “Control Structure for Versatile Content Control”; this application is further related to U.S. patent application Ser. No. ______ [Docket 382US5], entitled “Method for Creating Control Structure for Versatile Content Control”; this application is further related to U.S. patent application Ser. No. ______ [Docket 382US6], entitled “System for Creating Control Structure for Versatile Content Control”; this application is further related to U.S. patent application Ser. No. ______ [Docket 382US7], entitled “Method for Versatile Content Control with Partitioning”; this application is further related to U.S. patent application Ser. No. ______ [Docket 382US8], entitled “Versatile Content Control with Partitioning”; all of which are filed on the same day as the present application. These applications are incorporated in their entirety by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

0002This invention relates in general to memory systems, and in particular to a memory system with versatile content control features.

0003The computing device market is developing in the direction of including content storage on mobile storage devices so as to increase the average revenue by generating more data exchanges. This means that the content in a mobile storage medium has to be protected when used on a computing device. Content includes valuable data, which may be data owned by a party other than the one that manufactures or sells the storage device.

0004One type of storage device with encryption capability is described in U.S. Pat. No. 6,457,126. The capability provided by this device, is however, quite limited. It is therefore desirable to provide a memory system with more versatile content control features.

SUMMARY OF THE INVENTION

0005The protection of content in a mobile storage medium can involve the encryption of data in the medium so that only authorized users or applications have access to keys used for encrypting data stored in the medium. In some prior systems, the key used for encrypting and decrypting data is stored in devices external to the mobile storage medium. In such circumstances, the company or individual who owns proprietary interest in the content may not have much control over the usage of the content in the medium. Since the key used for encrypting data in the medium exists external to the medium, this key may be passed from one device to another in a manner not subject to control by the content proprietor. The owner of proprietor interest will be in the better position to control access to the content in the medium if the encryption-decryption key is stored in the medium itself and substantially inaccessible to external devices, according to one of the features of the invention.

0006By making the key essentially inaccessible from outside the medium, this feature provides portability to secured content. Thus, the storage device containing secured content ciphered with such a key can be used for access by a variety of host devices without the danger of security breach, since the device has exclusive control of access to the key. Only those host devices with the proper credentials are able to access the key.

0007To enhance the commercial value of the content stored in the mobile storage medium, it is desirable for the owner of proprietary interest in the content to be able to grant different permissions to different entities for accessing the content. Therefore another feature of the invention is based on the recognition that an access policy may be stored which grants different permissions (e.g. to different authorized entities) for accessing data stored in the medium. A system incorporating a combination of the two above features is particularly advantageous. On the one hand, the content owner or proprietor has the ability to control access to the content by using keys that are substantially inaccessible to external devices and at the same time has the ability to grant different permissions for accessing content in the medium. Thus, even where external devices gain access, their access may still be subject to the different permissions set by the content owner or proprietor recorded in the storage medium.

0008Yet another feature is based on the recognition that when the above-described policy, where different permissions are granted to different authorized entities, is implemented in a flash memory, this results in a particularly useful medium for content protection.

0009Many storage devices are not aware of file systems while many computer host devices read and write data in the form of files. According to another feature, the host device provides a key reference or ID, while the memory system generates a key value in response which is associated with the key ID, where the key value is used in cryptographic processing data in a file associated with the key ID. The host associates the key ID with the file to be processed cryptographically by the memory system. Thus the key ID is used by the computing device and memory as the handle through which the memory retains complete and exclusive control over the generation and use of the key value for cryptographic processes, while the host retains control of files.

0010In some mobile storage devices such as smart cards, the card controller manages the file system. In many other types of mobile storage devices, such as flash memories, magnetic or optical discs, the device controller is not aware of the file system; instead, the device controller relies on a host device (e.g. a personal computer, digital camera, MP3 player, personal digital assistants, cellular phones) to manage the file system. The various aspects of this invention may be readily incorporated into such types of storage devices where the device controller is not aware of the file system. This means that the various features of this invention may be practiced on a wide variety of existing mobile storage devices without requiring a re-design of such devices to make the device controller in such devices become aware of and able to manage the file system.

0011A tree structure stored in the storage medium provides control over what an entity can do even after gaining access. Each of the nodes of the tree specifies permissions by an entity who has gained entry through such node of the tree. Some trees have different levels, where the permission or permissions at a node of the tree has a predetermined relationship to permission or permissions at another node at a higher or lower or the same level in the same tree. By requiring entities to comply with the permissions so specified at each of the nodes, the tree feature of this application allows a content owner to control which entities can take action, and which actions each of the entities can take, irrespective of whether the tree has different levels.

0012To enhance the commercial value that can be provided by the mobile storage medium, it is desirable for mobile storage devices to be capable of supporting more than one application simultaneously. When two or more applications are accessing the mobile storage device at the same time, it can be important to be able to separate the operations of the two or more applications so that they do not interfere with one another in a phenomena referred to herein as crosstalk. Therefore another feature of the invention is based on the recognition that two or more trees which are preferably hierarchical may be provided for controlling access to the memory. Each tree comprises nodes at different levels for controlling access to data by a corresponding set of entities where a node of each tree specifies permission or permissions of the corresponding entity or entities for accessing memory data. The permission or permissions at a node of each of the trees has a predetermined relationship to permission or permissions at another node at a higher or lower level in the same tree. Preferably, there is no crosstalk between at least two of the trees.

0013From the above, it will be evident that trees are powerful structures that can be used for content security. One of the important controls provided is the control over the creation of trees. Thus, according to another feature of the invention, the mobile storage device may be provided with a system agent that is able to create at least one hierarchical tree comprising nodes at different levels for controlling access to data stored in the memory by corresponding entities. Each node of the tree specifies permission or permissions of a corresponding entity or entities for accessing memory data. The permission or permissions at the node of each of the trees has a predetermined relationship to permission or permissions at nodes at a higher or lower or the same level in the same tree. Thus, the mobile storage devices may be issued without any trees already created so that the purchaser of the devices has a free hand in creating hierarchical trees adapted to the applications the purchaser has in mind. Alternatively, the mobile storage devices may also be issued with the trees already created so that a purchaser does not have to go through the trouble of creating the trees. In both situations, preferably certain functionalities of the trees can become fixed after the devices are made so that they cannot be further changed or altered. This provides greater control over access to the content in the device by the content owner. Thus, in one embodiment, the system agent can preferably be disabled so that no additional trees can be created.

0014In some mobile storage devices, content protection is afforded by dividing the memory into separate areas where access to protected areas requires prior authentication. While such feature does provide some protection, it does not protect against a user who obtained a password by illicit means. Thus, another aspect of the invention is based on the recognition that a mechanism or structure may be provided to divide a memory into partitions and so that at least some data in the partitions can be encrypted with a key, so that in addition to authentication that is required for accessing some of the partitions, access to one or more keys may be required to decrypt the encrypted data in such partitions.

0015In some applications, it may be more convenient to the user to be able to log in the memory system using one application, and then be able to use different applications to access protected content without having to log in again. In such event, all of the content that the user wishes to access in this manner may be associated with a first account, so that all such content can be accessed via different applications (e.g. music player, email, cellular communication etc.) without having to log in multiple times. Then a different set of authentication information may then be used for logging in to access protected content that is in an account different from the first account, even where the different accounts are for the same user or entity.

0016The above-described features may be used individually, or may be combined in any combination, in storage systems to provide greater versatility of control and/or protection for the content owner.

BRIEF DESCRIPTION OF THE DRAWINGS

0017<figref idref="DRAWINGS">FIG. 1</figref> is a block diagram of a memory system in communication with the host device useful for illustrating this invention.

0018<figref idref="DRAWINGS">FIG. 2</figref> is a schematic view of different partitions of a memory and of unencrypted and encrypted files stored in different partitions where access to certain partitions and the encrypted files is controlled by access policies and authentication procedures to illustrate an embodiment of the invention.

0019<figref idref="DRAWINGS">FIG. 3</figref> is a schematic view of a memory illustrating the different partitions in the memory.

0020<figref idref="DRAWINGS">FIG. 4</figref> is a schematic view of file location tables for the different partitions of the memory shown in <figref idref="DRAWINGS">FIG. 3</figref> where some of the files in the partitions are encrypted to illustrate an embodiment of the invention.

0021<figref idref="DRAWINGS">FIG. 5</figref> is a schematic view of access control records in an access controlled record group and the associated key references to illustrate an embodiment of the invention.

0022<figref idref="DRAWINGS">FIG. 6</figref> is a schematic view of tree structures formed by access controlled records groups and access controlled records to illustrate an embodiment of the invention.

0023<figref idref="DRAWINGS">FIG. 7</figref> is a schematic diagram of a tree illustrating three hierarchical trees of access controlled record groups to illustrate a process of formation of the trees.

0024<figref idref="DRAWINGS">FIGS. 8A and 8B</figref> are flow charts illustrating the processes carried out by a host device and a memory device such as a memory card for creating and using a system access control record.

0025<figref idref="DRAWINGS">FIG. 9</figref> is a flow chart illustrating a process using a system access control record to create an access controlled record group to illustrate the invention.

0026<figref idref="DRAWINGS">FIG. 10</figref> is a flow chart illustrating a process for creating an access control record.

0027<figref idref="DRAWINGS">FIG. 11</figref> is a schematic view of two access control record groups useful for illustrating a particular application of the hierarchical tree.

0028<figref idref="DRAWINGS">FIG. 12</figref> is a flow chart illustrating a process for delegation of specific rights.

0029<figref idref="DRAWINGS">FIG. 13</figref> is a schematic view of an access controlled record group and an access control record to illustrate the process of delegation of <figref idref="DRAWINGS">FIG. 12</figref>.

0030<figref idref="DRAWINGS">FIG. 14</figref> is a flowchart illustrating the process for creating a key for the purpose of encryption and/or decryption.

0031<figref idref="DRAWINGS">FIG. 15</figref> is a flow chart illustrating a process for removing access rights and/or permission for data access according to an accessed controlled record.

0032<figref idref="DRAWINGS">FIG. 16</figref> is a flow chart illustrating a process for requesting access when access rights and/or permission to access has been deleted or has expired.

0033<figref idref="DRAWINGS">FIGS. 17A and 17B</figref> are schematic views illustrating an organization of a rule structure for authentication and policies for granting access to cryptographic keys to illustrate another embodiment of the invention.

0034<figref idref="DRAWINGS">FIG. 18</figref> is a flow diagram illustrating sessions of authentication and access when some sessions are open.

0035<figref idref="DRAWINGS">FIG. 19-22</figref> are flow charts illustrating different authentication processes.

0036For simplicity in description, identical components are labeled by the same numerals in this application.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

0037An example memory system in which the various aspects of the present invention may be implemented is illustrated by the block diagram of <figref idref="DRAWINGS">FIG. 1</figref>. As shown in <figref idref="DRAWINGS">FIG. 1</figref>, the memory system <b>10</b> includes a central processing unit (CPU) <b>12</b>, a buffer management unit (BMU) <b>14</b>, a host interface module (HIM) <b>16</b> and a flash interface module (FIM) <b>18</b>, a flash memory <b>20</b> and a peripheral access module (PAM) <b>22</b>. Memory system <b>10</b> communicates with a host device <b>24</b> through a host interface bus <b>26</b> and port <b>26</b><i>a. </i>The flash memory <b>20</b> which may be of the NAND type, provides data storage for the host device <b>24</b>. The software code for CPU <b>12</b> may also be stored in flash memory <b>20</b>. FIM <b>18</b> connects to the flash memory <b>20</b> through a flash interface bus <b>28</b> and port <b>28</b><i>a. </i>HIM <b>16</b> is suitable for connection to a host system like a digital camera, personal computer, personal digital assistants (PDA), digital media players, MP-3 players, cellular telephones or other digital devices. The peripheral access module <b>22</b> selects the appropriate controller module such as FIM, HIM and BMU for communication with the CPU <b>12</b>. In one embodiment, all of the components of system <b>10</b> within the dotted line box may be enclosed in a single unit such as in memory card or stick <b>10</b>′ and preferably encapsulated.

0038While the invention is illustrated herein by reference to flash memories, the invention may also be applicable to other types of memories, such as magnetic disks, optical CDs, as well as all other types of rewrite-able non volatile memory systems.

0039The buffer management unit <b>14</b> includes a host direct memory access (HDMA) <b>32</b>, a flash direct memory access (FDMA) <b>34</b>, an arbiter <b>36</b>, a buffer random access memory (BRAM) <b>38</b> and a crypto-engine <b>40</b>. The arbiter <b>36</b> is a shared bus arbiter so that only one master or initiator (which can be HDMA <b>32</b>, FDMA <b>34</b> or CPU <b>12</b>) can be active at any time and the slave or target is BRAM <b>38</b>. The arbiter is responsible for channeling the appropriate initiator request to the BRAM <b>38</b>. The HDMA <b>32</b> and FDMA <b>34</b> are responsible for data transported between the HIM <b>16</b>, FIM <b>18</b> and BRAM <b>38</b> or the CPU random access memory (CPU RAM)<b>12</b><i>a. </i>The operation of the HDMA <b>32</b> and of the FDMA <b>34</b> are conventional and need not be described in detail herein. The BRAM <b>38</b> is used to store data passed between the host device <b>24</b> and flash memory <b>20</b>. The HDMA <b>32</b> and FDMA <b>34</b> are responsible for transferring the data between HIM <b>16</b>/FIM <b>18</b> and BRAM <b>38</b> or the CPU RAM <b>12</b><i>a </i>and for indicating sector completion.

0040For improved security of the content stored in memory <b>20</b>, memory system <b>10</b> generates the key value(s) that are used for encryption and/or decryption, where this value(s) is substantially not accessible to external devices such as host device <b>24</b>. However, encryption and decryption is typically done file by file, since the host device reads and writes data to memory system <b>10</b> in the form of files. Like many other types of storage devices, memory device <b>10</b> is not aware of files or file systems. While memory <b>20</b> does store a file allocation table (FAT) where the logical addresses of the files are identified, the FAT is typically accessed and managed by the host device <b>24</b> and not by the controller <b>12</b>. Therefore, in order to encrypt data in a particular file, the controller <b>12</b> will have to rely on the host device to send the logical addresses of the data in the file in memory <b>20</b>, so that the data of the particular file can be found and encrypted and/or decrypted by system <b>10</b> using the key value(s) available only to system <b>10</b>.

0041To provide a handle for both the host device <b>24</b> and memory system <b>10</b> to refer to the same key(s) for cryptographically processing data in files, the host device provides a reference for each of the key values generated by system <b>10</b>, where such reference may simply be a key ID. Thus, the Host <b>24</b> associates each file that is cryptographically processed by system <b>10</b> with a key ID, and the system <b>10</b> associates each key value that is used to cryptographically process data with a key ID provided by the host. Thus, when the host requests that a file be cryptographically processed, it will send the request along with a key ID along with the logical addresses of data to be fetched from or stored in memory <b>20</b> to system <b>10</b>. System <b>10</b> generates a key value and associates the key ID provided by the host <b>24</b> with such value, and performs the cryptographic processing. In this manner, no change needs to be made in the manner memory system <b>10</b> operates while allowing it to completely control the cryptographic processing using the key(s), including exclusive access to the key value(s). In other words, system <b>10</b> continues to allow the host <b>24</b> to manage the files by having exclusive control of FAT, while it maintains exclusive control for the generation and management of the key value(s) used for cryptographic processing. The host device <b>24</b> has no part in the generation and management of the key value(s) used for cryptographic processing of data.

0042The key ID provided by the host <b>24</b> and the key value generated by the memory system form two attributes of a quantity referred to below as the “content encryption key” or CEK in one of the embodiments. While the host <b>24</b> may associate each key ID with one or more files, host <b>24</b> may also associate each key ID with unorganized data or data organized in any manner, and not limited to data organized into complete files.

0043In order for a user or application to gain access to protected content or area in system <b>10</b>, it will need to be authenticated using a credential which is pre-registered with system <b>10</b>. A credential is tied to the access rights granted to the particular user or application with such credential. In the pre-registration process, system <b>10</b> stores a record of the identity and credential of the user or application, and the access rights associated with such identity and credential determined by the user or application and provided through the host <b>24</b>. After the pre-registration has been completed, when the user or application requests to write data to memory <b>20</b>, it will need to provide through the host device its identity and credential, a key ID for encrypting the data, and the logical addresses where the encrypted data is to be stored. System <b>10</b> generates a key value and associates this value with the key ID provided by the host device, and stores in its record or table for this user or application the key ID for the key value used to encrypt the data to be written. It then encrypts the data and stores the encrypted data at the addresses designated by the host as well as the key value it generated.

0044When a user or application requests to read encrypted data from memory <b>20</b>, it will need to provide its identity and credential, the key ID for the key previously used to encrypt the requested data, and the logical addresses where the encrypted data is stored. System <b>10</b> will then match the user or application identity and credential provided by the host to those stored in its record. If they match, system <b>10</b> will then fetch from its memory the key value associated with the key ID provided by the user or application, decrypt the data stored at the addresses designated by the host device using the key value and send the decrypted data to the user or application.

0045By separating the authentication credentials from the management of keys used for cryptographic processing, it is then possible to share rights to access data without sharing credentials. Thus, a group of users or applications with different credentials can have access to the same keys for accessing the same data, while users outside this group have no access. While all users or applications within a group may have access to the same data, they may still have different rights. Thus, some may have read only access, while others may have write access only, while still others may have both. Since system <b>10</b> maintains a record of the users or application identities and credentials, the key IDs they have access to, and the associated access rights to each of the key IDs, it is possible for system <b>10</b> to add or delete key IDs and alter access rights associated with such key IDs for particular users or applications, to delegate access rights from one user or application to another, or even to delete or add records or tables for users or applications, all as controlled by a properly authenticated host device. The record stored may specify that a secure channel is required for accessing certain keys. Authentication may be done using symmetric or asymmetric algorithms as well as passwords.

0046Especially important is the portability of the secured content in the memory system <b>10</b>. Since the key value is generated by the memory system and substantially not available to external systems, when the memory system or a storage device incorporating the system is transferred from one external system to another, security of the content stored therein is maintained, and external systems are not able to access such content unless they have been authenticated in a manner completely controlled by the memory system. Even after being so authenticated, access is totally controlled by the memory system, and external systems can access only in a manner controlled according to preset records in the memory system. If a request does not comply with such records, the request will be denied.

0047To provide greater flexibility in protecting content, it is envisioned that certain areas of the memory referred to below as partitions can be accessed only by properly authenticated users or applications. When combined with the above described features of key-based data encryption, system <b>10</b> provides greater data protection capability. As shown in <figref idref="DRAWINGS">FIG. 2</figref>, the flash memory <b>20</b> may have its storage capacity divided into a number of partitions: a user area or partition and custom partitions. The user area or partition P<b>0</b> is accessible to all users and applications without authentication. While all bit values of data stored in the user area can be read or written to by any application or user, if the data read is encrypted, the user or application without authority to decrypt would not be able to access the information represented by the bit values stored in a user area. This is illustrated, for example, by files <b>102</b> and <b>104</b> stored in user area P<b>0</b>. Also stored in the user area are unencrypted files such as <b>106</b> which can be read and understood by all applications and users. Thus, symbolically, the files that are encrypted are shown with locks associated with them such as for files <b>102</b> and <b>104</b>.

0048While an encrypted file in a user area P<b>0</b> cannot be understood by unauthorized applications or users, such applications or users may still be able to delete or corrupt the file, which may be undesirable for some applications. For this purpose, memory <b>20</b> also includes protected custom partitions such as partitions P<b>1</b> and P<b>2</b> which cannot be accessed without prior authentication. The authentication process permitted in the embodiments in this application is explained below.

0049As also illustrated in <figref idref="DRAWINGS">FIG. 2</figref>, a variety of users or applications may access the files in memory <b>20</b>. Thus users <b>1</b> and <b>2</b>, and applications <b>1</b>-<b>4</b> (running on devices) are shown in <figref idref="DRAWINGS">FIG. 2</figref>. Before these entities are allowed to access protected content in memory <b>20</b>, they are first authenticated by an authentication process in a manner explained below. In this process, the entity that is requesting access needs to be identified at the host side for role based access control. Thus, the entity requesting access first identifies itself by supplying information such as “I am application 2 and I wish to read file 1.” Controller <b>12</b> then matches the identity, authentication information and request against the record stored in memory <b>20</b> or controller <b>12</b>. If all requirements are met, access is then granted to such entity. As illustrated in <figref idref="DRAWINGS">FIG. 2</figref>, user <b>1</b> is allowed to read from and write to file <b>101</b> in partition P<b>1</b>, but can only read files <b>102</b> and <b>104</b> in addition to user <b>1</b> having unrestricted rights to read from and write to files <b>106</b> in P<b>0</b>. User <b>2</b>, on the other hand, is not allowed access to file <b>101</b> and <b>104</b> but has read and write access to file <b>102</b>. As indicated in <figref idref="DRAWINGS">FIG. 2</figref>, users <b>1</b> and <b>2</b> have the same login algorithm (AES) while applications <b>1</b> and <b>3</b> have different login algorithms (e.g. RSA and 001001) which are also different from those of users <b>1</b> and <b>2</b>.

0050The Secure Storage Application (SSA) is a security application of the memory system <b>10</b>, and illustrates an embodiment of the invention, which can be used to implement many of the above-identified features. SSA may be embodied as software or computer code with database stored in the memory <b>20</b> or a non-volatile memory (not shown) in CPU <b>12</b>, and is read into RAM <b>12</b><i>a </i>and executed by CPU <b>12</b>. The acronyms used in reference to the SSA are set forth in the table below: <tables id="TABLE-US-00001" num="1"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217PT" align="center" /><thead><row><entry /></row><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>Definitions, Acronyms &amp; Abbreviations</entry></row><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row></thead><tbody valign="top"><row><entry /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="OFFSET" colwidth="21PT" align="left" /><colspec colname="1" colwidth="49PT" align="left" /><colspec colname="2" colwidth="147PT" align="left" /><tbody valign="top"><row><entry /><entry>ACR</entry><entry>Access Control Records</entry></row><row><entry /><entry>AGP</entry><entry>ACR Group</entry></row><row><entry /><entry>CBC</entry><entry>Chain Block Cipher</entry></row><row><entry /><entry>CEK</entry><entry>Content Encryption Key</entry></row><row><entry /><entry>ECB</entry><entry>Electronic Codebook</entry></row><row><entry /><entry>ACAM</entry><entry>ACR Attributes Management</entry></row><row><entry /><entry>PCR</entry><entry>Permissions Control Record</entry></row><row><entry /><entry>SSA</entry><entry>Secure Storage Application</entry></row><row><entry /><entry>Entity</entry><entry>Any thing that has real and individual</entry></row><row><entry /><entry /><entry>existence (host side) that logs in the SSA</entry></row><row><entry /><entry /><entry>and thus utilizes its functionalities.</entry></row><row><entry /><entry namest="OFFSET" nameend="2" align="center" rowsep="1" /></row></tbody></tgroup></table></tables><br /> SSA System Description

0051Data security, integrity and access control are the major roles of the SSA. The data are files that would otherwise be stored plainly on a mass-storage device of some kind. The SSA system sits atop of the storage system and adds the security layer for the stored host files.

0052The main task of the SSA is to manage the different rights associated with the stored (and secured) content in the memory. The memory application needs to manage multiple users and content rights to multiple stored content. Host applications from their side, see drives and partitions that are visible to such applications, and file allocation tables (FATs) that manage and portray the locations of the stored files on the storage device.

0053In this case the storage device uses NAND flash chip divided to partitions, although other mobile storage devices may also be used and are within the scope of this invention. These partitions are continuous threads of logical addresses, where a start and an end address define their boundaries. Restrictions may therefore be imposed on access to hidden partitions, if desired, by means of software (such as software stored in memory <b>20</b>) that associates such restrictions with the addresses within such boundaries. Partitions are fully recognizable to the SSA by their logical address boundaries that are managed by it. The SSA system uses partitions to physically secure data from unauthorized host applications. To the host, the partitions are a mechanism of defining proprietary spaces in which to store data files. These partitions can either be public, where anyone with access to the storage device can see and be aware of the partition's presence on the device, or private or hidden, where only the selected host applications have access to and are aware of their presence in the storage device.

0054<figref idref="DRAWINGS">FIG. 3</figref> is a schematic view of a memory illustrating the partitions of the memory: P<b>0</b>, P<b>1</b>, P<b>2</b> and P<b>3</b> (obviously fewer or more partitions than four may be employed), where P<b>0</b> is a public partition which can be accessed by any entity without authentication.

0055A private partition (such as P<b>1</b>, P<b>2</b> or P<b>3</b>) hides the access to the files within it. By preventing the host from accessing the partition, the flash device (e.g. flash card) delivers protection of the data files inside the partition. This kind of protection, however, engulfs all of the files residing in the hidden partition by imposing restrictions on access to data stored at the logical addresses within the partition. In other words, the restrictions are associated with a range of logical addresses. All of the users/hosts that have access to that partition will have unlimited access to all of the files inside. To isolate different files from one another—or groups of files—the SSA system provides another level of security and integrity per file—or groups of files—using keys and key references or Key IDs. A key reference or key ID of a particular key value used for encrypting data at different memory addresses can be analogized to a container or domain that contains the encrypted data. For this reason, in <figref idref="DRAWINGS">FIG. 4</figref>, the key references or key IDs (e.g. “key 1” and “key 2”) are shown graphically as areas surrounding the files encrypted using the key values associated with the key IDs.

0056In reference to <figref idref="DRAWINGS">FIG. 4</figref>, for example, File A is accessible to all entities without any authentication, since it is shown as not enclosed by any key ID. Even though File B in the public partition can be read or overwritten by all entities, it contains data encrypted with a key with ID “key 1”, so that the information contained in File B is not accessible to an entity unless such entity has access to such key. In this manner using key values and key references or Key IDs provide logical protection only, as opposed to the type of protection provided by the partition described above. Hence, any host that can access a partition (public or private) is capable of reading or writing the data in the entire partition, including the encrypted data. However, since the data is encrypted, unauthorized users can only corrupt it. They preferably cannot alter the data without detection or use it. By restricting the access to the encryption and/or decryption keys, this feature can allow only the authorized entities to use the data. Files B and C are also encrypted using a key with key ID “key 2” in P<b>0</b>.

0057Data confidentiality and integrity can be provided through symmetric encryption methods that use Content Encryption Keys (CEK), one per CEK. In the SSA embodiment, the CEKs are generated by the flash device (e.g. flash card), used internally only, and kept as secrets from the outside world. The data that is encrypted or ciphered may also be either hashed or the cipher is chain blocked to ensure data integrity.

0058Not all the data in the partition is encrypted by different keys and associated with different key IDs. Certain logical addresses either in public or user files or in the operating system area (i.e. FAT) may not be associated with any key or key reference, and thus are available to any entity that can access the partition itself.

0059An entity that calls for the ability to create keys and partitions as well as writing and reading data from them or using the keys, needs to login to the SSA system through an Access Control Record (ACR). The privileges of an ACR in the SSA system are called Actions. Every ACR may have Permissions to perform Actions of the following three categories: Creating partitions and keys/key IDs, accessing partitions and keys and creating/updating other ACRs.

0060ACRs are organized in groups called ACR Groups or AGPs. Once an ACR has successfully authenticated, the SSA system opens a Session through which any of the ACR's actions can be executed.

0000User Partition(s)

0061The SSA system manages one or more public partitions, also referred to as the user partition(s). This partition exists on the storage device and is a partition or partitions that can be accessed through the standard read write commands of the storage device. Getting information regarding the size of the partition(s) as well as its existence on the device preferably cannot be hidden from the host system.

0062The SSA system enables accessing this partition(s) either through the standard read write commands or the SSA commands. Therefore, accessing the partition preferably cannot be restricted to specific ACRs. The SSA system, however, can enable the host devices to restrict the access to the user partition. Read and write accesses can be enabled/disabled individually. All four combinations (e.g. write only, read only (write protect), read and write and no access) are allowed.

0063The SSA system enables ACRs to associate key IDs with files within the user partition and encrypt individual files using keys associated with such key IDs. Accessing encrypted files within the user partitions as well as setting the access rights to the partitions will be done using the SSA command set (refer to Appendix A for detailed description of the SSA commands—In the Appendix, key ID is referred to as “domain”).The above features also apply to data not organized into files.

0000SSA Partitions

0064These are hidden (from the host operating system or OS) partitions that can be accessed only through the SSA commands. The SSA system will preferably not allow the host device to access an SSA partition, other than through a session (described below) established by logging onto an ACR. Similarly, preferably the SSA will not provide information regarding the existence, size and access permission of an SSA partition, unless this request is coming through an established session.

0065Access rights to partitions are derived from the ACR permissions. Once an ACR is logged into the SSA system, it can share the partition with other ACRs (described below). When a partition is created, the host provides a reference name or ID (e.g. P<b>0</b>-P<b>3</b> in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>) for the partition. This reference is used in further read and write commands to the partition.

0000Partitioning of the Storage Device

0066All available storage capacity of the device is preferably allocated to the user partition and the currently configured SSA partitions. Therefore, any repartition operation may involve reconfiguration of the existing partitions. The net change to the device capacity (sum of sizes of all partitions) will be zero. The IDs of the partitions in the device memory space are defined by the host system.

0067The host system can either repartition one of the existing partitions into two smaller ones or, merge two existing partitions (which may or may not be adjacent) into one. The data in the divided or merged partitions can be either erased or left untouched, at the host's discretion.

0068Since repartitioning of the storage device may cause loss of data (either because it was erased or moved around in the logical address space of the storage device) severe restrictions on repartitioning are administered by the SSA system. Only an ACR residing in a root AGP (explained below) is allowed to issue a repartition command and it can only reference partitions owned by it. Since the SSA system is not aware of how data is organized in the partitions (FAT or other file system structure) it is the host's responsibility to reconstruct these structures any time the device is repartitioned.

0069Repartitioning of the user partition will change the size and other attributes of this partition as seen by the host OS.

0070After repartitioning, it is the host system's responsibility to make sure any ACR in the SSA system is not referencing the non-existing partitions. If these ACRs are not deleted or updated appropriately, future attempts, on behalf of these ACRs, to access the non-existing partitions will be detected and rejected by the system. Similar care is taken, regarding deleted keys and key IDs.

0000Keys, Key IDs and Logical Protection

0071When a file is written to a certain hidden partition, it is hidden from the general public. But, once an entity (hostile or not) gets knowledge and access to this partition the file becomes available and plain to see. To further secure the file, the SSA can encrypt it in the hidden partition, where the credentials for accessing the key for decrypting the file are preferably different from those for accessing the partition. Due to the fact that files are not something that the SSA is aware of (totally controlled and managed by the host), associating a CEK with a file is a problem. Linking the file to something the SSA acknowledges—the key ID, rectifies this. Thus, when a key is created by the SSA, the host associates the key ID for this key with the data encrypted using the key created by the SSA.

0072The key value and key ID provide logical security. All data associated with a given key ID, regardless of its location, is ciphered with the same content encryption key (CEK) whose reference name or key ID is uniquely provided at creation by the host application. If an entity obtains access to a hidden partition (by authenticating through an ACR) and wishes to either read or write an encrypted file within this partition, it needs to have access to the key ID that is associated with the file. When granting access to the key for this key ID, the SSA loads the key value in CEK associated with this key ID and either decrypts the data before sending it to the host or encrypts the data before writing it to the flash memory <b>20</b>. A key value in CEK associated with a key ID is randomly created once by the SSA system and maintained by it. No one outside the SSA system has knowledge or access to this key value in CEK. The outside world only provides and uses a reference or key ID, not the key value in CEK. The key value is entirely managed and only accessible by the SSA

0073The SSA system protects the data associated with the key ID using any one (user defined) of the following cipher modes (the actual cryptographic algorithms used, as well as the key values in CEKs, are system controlled and not revealed to the outside world):

0074Block mode—Data is divided into blocks, each one of them, encrypted individually. This mode is generally considered less secure and susceptive to dictionary attacks, However, it will allow users to randomly access any one of the data blocks.

0075Chained mode—Data is divided into blocks, which are chained during the encryption process. Every block is used as one of the inputs to the encryption process of the next one. This mode, although considered as more secure, requires that the data is always written and read sequentially from start to end, creating an overhead not always acceptable to the users.

0076Hashed—Chain mode with the additional creation of a data digest that can be used for validating data integrity.

0000ACRs and Access Control

0077The SSA is designed to handle multiple applications where each one of them is represented as a tree of nodes in the system database. Mutual exclusion between the applications is achieved by ensuring no cross talk between the tree branches.

0078In order to gain access to the SSA system, an entity needs to establish a connection via one of the system's ACRs. Login procedures are administered by the SSA system according to the definitions embedded in the ACR the user chose to connect with.

0079The ACR is an individual login point to the SSA system. The ACR holds the login credentials and the authentication method. Also residing in the record are the login permissions within the SSA system, among which are the read and write privileges. This is illustrated in <figref idref="DRAWINGS">FIG. 5</figref>, which illustrates n ACRs in the same AGP. This means that at least some of the n ACRs may share access to the same key. Thus, ACR #<b>1</b> and ACR #n share access to a key with key ID “key 3”, where ACR#<b>1</b> and ACR#n are the ACR IDs, and “key 3” is a key ID for the key that is used to encrypt data associated with “key 3”. The same key can also be used to encrypt and/or decrypt multiple files, or multiple sets of data.

0080The SSA system supports several types of login onto the system where authentication algorithms and user credentials may vary, as may the user's privileges in the system once he logged in successfully. <figref idref="DRAWINGS">FIG. 5</figref> again illustrates different login algorithms and credentials. ACR#<b>1</b> requires a password login algorithm and password as credential whereas ACR#<b>2</b> requires a PKI (public key infrastructure) login algorithm and public key as credential. Thus, to login, an entity will need to present a valid ACR ID, as well as the correct login algorithm and credential.

0081Once an entity is logged into an ACR of the SSA system, its permissions—its rights to use SSA commands—are defined in the Permissions Control Record (PCR) which is associated with the ACR. In <figref idref="DRAWINGS">FIG. 5</figref>, ACR#<b>1</b> grants read only permission to data associated with “key 3”, and ACR #<b>2</b> grants permission to read and write data associated with “key 5” according to the PCR shown.

0082Different ACRs may share common interests and privileges in the system such as in keys with which to read and write. To accomplish that, ACRs with something in common are grouped in AGPs-ACR. Groups. Thus, ACR #<b>1</b> and ACR #n share access to a key with key ID “key 3”.

0083AGPs and, the ACRs within, are organized in hierarchical trees and so aside from creating secure keys that keep sensitive data secure; an ACR can preferably also create other ACR entries that correspond to his key ID/partitions. These ACR children will have the same or less permissions as their father—creator and, may be given permissions for keys the father ACR himself created. Needless to add, the children ACRs get access permissions to any key that they create. This is illustrated in <figref idref="DRAWINGS">FIG. 6</figref>. Thus, all of the ACRs in AGP <b>120</b> were created by ACR <b>122</b> and two of such ACRs inherit from ACR <b>122</b> permission(s) to access to data associated with “key 3”.

AGP

0084Logging onto the SSA system is done by specifying an AGP and an ACR within the AGP.

0085Every AGP has a unique ID (reference name), which is used as an index to its entry in the SSA database. The AGP name is provided to the SSA system, when the AGP is created. If the provided AGP name already exists in the system, the SSA will reject the creation operation.

0086AGPs are used to administer restrictions on delegation of access and management permissions as will be described in the following sections. One of the functions served by the two trees in <figref idref="DRAWINGS">FIG. 6</figref> is to administer the access by entirely separate entities, such as two different applications, or two different computer users. For such purposes, it may be important for the two access processes to be substantially independent of one another (i.e. substantially no cross-talk), even though both occur at the same time. This means that the authentication, permissions as well as the creation of additional ACRs and AGPs in each tree are not connected to and do not depend on those of the other tree. Hence, when the SSA system is used in memory <b>10</b>, this allows the memory system <b>10</b> to serve multiple applications simultaneously. It also allows the two applications to access two separate sets of data independently of one another (e.g. a set of photographs and a set of songs). This is illustrated in <figref idref="DRAWINGS">FIG. 6</figref>. Thus, the data associated with “keys 3”, “key X” and “key Z” for the application or user accessing via nodes (ACRs) in the tree in the top portion of <figref idref="DRAWINGS">FIG. 6</figref> may comprise photographs. The data associated with “key 5” and “key Y” for the application or user accessing via nodes (ACRs) of the tree in the bottom portion of <figref idref="DRAWINGS">FIG. 6</figref> may comprise songs. The ACR that created the AGP has the permission to delete it only when the AGP is empty of ACR entries

0000The Entity's SSA Entry Point: Access Control Record (ACR)

0087An ACR in the SSA system describes the way the entity is permitted to log into the system. When an entity logs into the SSA system it needs to specify the ACR that corresponds to the authentication process it is about to perform. An ACR includes a Permissions Control Record (PCR) that illustrates the granted actions the user can execute once authenticated as defined in the ACR as illustrated in <figref idref="DRAWINGS">FIG. 5</figref>. The host side entity provides all of the ACR data fields.

0088When an entity has successfully logged onto an ACR, the entity will be able to query on all of the ACR's partition and key access permissions and ACAM permissions (explained below).

ACR ID

0089When an SSA system entity initiates the login process it needs to specify the ACR ID (as provided by the host when the ACR was created) that corresponds to the login method so that the SSA will set up the correct algorithms and select the correct PCR when all login requirements have been met. The ACR ID is provided to the SSA system when the ACR is created.

0000Login/Authentication Algorithm

0090The authentication algorithm specifies what sort of login procedure will be used by the entity, and what kind of credentials are needed to provide proof of user's identity. The SSA system supports several standard login algorithms, ranging from no procedure (and no credential) and password-based procedures to a two-way authentication protocols based on either symmetric or asymmetric cryptography.

0000Credentials

0091The entity's credentials correspond to the login algorithm and are used by the SSA to verify and authenticate the user. An example for credential can be a password/PIN-number for password authentication, AES-key for AES authentication, etc. The type/format of the credentials (i.e. the PIN, the symmetric key, etc . . . ) is predefined and derived from the authentication mode; they are provided to the SSA system when the ACR is created. The SSA system has no part in defining, distributing and managing these credentials, with the exception of PKI based authentication where the device (e.g. flash card) can be used to generate the RSA key pair and the public key can be exported for certificate generation.

0000The Permissions Control Record (PCR)

0092The PCR shows what is granted to the entity after logging into the SSA system and passing the ACR's authentication process successfully. There are three types of permission categories: Creation permissions for partition and keys, Access permissions to partitions and keys and management permissions for Entity-ACR Attributes

0000Accessing Partitions

0093This section of the PCR contains the list of partitions (using their IDs as provided to the SSA system) the entity can access upon completing the ACR phase successfully. For each partition the access type may be restricted to write-only or read-only or may specify full write/read access rights. Thus, the ACR#<b>1</b> in <figref idref="DRAWINGS">FIG. 5</figref> has access to partition #<b>2</b> and not partition #<b>1</b>. The restrictions specified in the PCR apply to the SSA partitions and the public partition.

0094The public partition can be accessed either by regular read and write commands to the device (e.g. flash card) hosting the SSA system, or by SSA commands. When a root ACR (explained below) is created with the permission to restrict the public partition, he can pass it on to his children. An ACR can preferably only restrict the regular read and write commands from accessing the public partition. ACRs in the SSA system can be restricted preferably only upon their creation. Once an ACR has the permission to read/write from/to the public partition, preferably it cannot be taken away.

0000Accessing Key IDs

0095This section of the PCR contains the data associated with the list of key IDs (as provided to the SSA system by the host) the entity can access when the ACR policies have been met by the entity's login process. The key ID specified is associated with a file/files that reside in the partition appearing in the PCR. Since the key IDs are not associated with logical addresses in the device (e.g. flash card), when more than one partition is associated with a specific ACR, the files can be in either one of the partitions. The key IDs specified in the PCR can have each, a different set of access rights. Accessing data pointed to by key IDs can be restricted to write-only or read-only or may specify full write/read access rights.

0000ACR Attributes Management (ACAM)

0096This section describes how in certain cases the ACR's system attributes can be changed.

0097The ACAM actions that may be permitted in the SSA system are:

0098Create/delete/update AGPs and ACR.

0099Create/delete Partitions and Keys.

0100Delegate access rights to keys and partitions.

0101A father ACR preferably cannot edit ACAM permissions. This would preferably require the deletion and recreation of the ACR. Also the access permission to a key ID created by the ACR can preferably not be taken away.

0102Create/delete/update AGPs and ACR

0103An ACR may have the capacity to create other ACRs and AGPs. Creating ACRs also may mean delegating them some or all of the ACAM permissions possessed by their creator. Having the permission to create ACRs means having the permission for the following actions:

01041. Define and edit the child's credentials—the authentication method preferably cannot be edited once set by the creating ACR. The credentials may be altered within the boundary of the authentication algorithm that is already defined for the child.

01052. Delete an ACR.

01063. Delegate the creating permission to the child ACR (thus having grandchildren).

0107An ACR with the permissions to create other ACRs has the permission to delegate the unblocking permission to ACRs it creates (although it probably does not have the permission to unblock ACRs). The father ACR will place in the child ACR a reference to his unblocker.

0108The father ACR is the only ACR that has the permission to delete his child ACR. When an ACR deletes a lower level ACR that he created, then all ACRs spawned by this lower-level ACR are automatically deleted as well. When an ACR is deleted then all the key IDs and partitions that it created are deleted.

0109There are two exceptions by which an ACR can update its own record:

0110Passwords/PINs, although set by the creator ACR, can be updated only by the ACR that includes them.

0111A root ACR may delete itself and the AGP that it resides in.

0000Delegate Access Rights to Keys and Partitions

0112ACRs and their AGPs are assembled in hierarchical trees where the root AGP and the ACRs within are at the top of the tree (e.g. root AGPs <b>130</b> and <b>132</b> in <figref idref="DRAWINGS">FIG. 6</figref>). There can be several AGP trees in the SSA system though they are totally separated from one another. An ACR within an AGP can delegate access permissions to its keys to all ACRs within the same AGP that it is in, and to all the ACRs created by them. The permission to create keys preferably includes the permission to delegate access permissions to use the keys.

0113Permissions to keys are divided into three categories:

01141. Access—this defines the access permissions for the key i.e. Read, Write.

01152. Ownership—an ACR that created a key is by definition its owner. This ownership can be delegated from one ACR to another (provided that they are in the same AGP or in a child AGP). An ownership of a key provides the permission to delete it as well as delegate permissions to it.

01163. Access Rights Delegation—this permission enables the ACR to delegate the rights he holds.

0117An ACR can delegate access permissions to partitions he created as well as other partitions he has access permissions to.

0118The permission delegation is done by adding the names of the partitions and key IDs to the designated ACR's PCR. Delegating key access permissions may either be by the key ID or by stating that access permission is for all of the created keys of the delegating ACR.

0119Blocking and Unblocking of ACRs

0120An ACR may have a blocking counter which increments when the entity's ACR authentication process with the system is unsuccessful. When a certain maximum number (MAX) of unsuccessful authentications is reached, the ACR will be blocked by the SSA system.

0121The blocked ACR can be unblocked by another ACR, referenced by the blocked ACR. The reference to the unblocking ACR is set by its creator. The unblocking ACR preferably is in the same AGP as the creator of the blocked ACR and has the “unblocking” permission.

0122No other ACR in the system can unblock the blocked ACR. An ACR may be configured with a blocking counter but without an unblocker ACR. In this case, if this ACR get blocked it cannot be unblocked.

0000Root AGP—Creating an Application Database

0123The SSA system is designed to handle multiple applications and isolate the data of each one of them. The tree structure of the AGP system is the main tool used to identify and isolate application specific data. The root AGP is at the tip of an application SSA database tree and adheres to somewhat different behavior rules. Several root AGPs can be configured in the SSA system. Two root AGPs <b>130</b> and <b>132</b> are shown in <figref idref="DRAWINGS">FIG. 6</figref>. Obviously fewer or more AGPs may be used and are within the scope of this invention.

0124Registering the device (e.g. flash card) for a new application and/or issue credentials of a new applications for the device are done through the process of adding new AGP/ACR tree to the device.

0125The SSA system supports three different modes of root AGP creation (as well as all of the ACRs of the root AGP and their permissions):

01261. Open: Any user or entity without requiring any sort of authentication, or users/entities authenticated through the system ACR (explained below), can create a new root AGP. The open mode enables creation of root AGPs either without any security measures while all data transfer is done on an open channel (i.e. in the secure environment of an issuance agency) or, through a secure channel established through the system ACR authentication (i.e. Over The Air (OTA) and post issuance procedures).

0127If the system ACR is not configured (this is an optional feature) and the root AGP creation mode is set to Open, only the open channel option is available.

01282. Controlled: Only entities authenticated through the System ACR can create a new root AGP. The SSA system cannot be set to this mode if system ACR is not configured.

01293. Locked: Creation of root AGPs is disabled and no additional root AGPs can be added to the system

0130Two SSA commands control this feature (these commands are available to any user/entity without authentication):

01311. Method configuration command—Used to configure the SSA system to use any one of the three root AGP creation modes. Only the following mode changes are allowed: Open→Controlled, Controlled→Locked (i.e. if the SSA system is currently configured as Controlled, it can only be changed to locked).

01322. Method configuration lock command—Used to disable the method configuration command and permanently lock the currently selected method.

0133When a root AGP is created, it is in a special initializing mode that enables the creation and configuration of its ACRs (using the same access restrictions that applied to the creation of the root AGP). At the end of the root AGP configuration process, when the entity explicitly switches it to operating mode, the existing ACRs can no longer be updated and additional ACRs can no longer be created

0134Once a root AGP is put in standard mode it can be deleted only by logging into the system through one of its ACRs that is assigned with the permission to delete the root AGP. This is another exception of root AGP, in addition to the special initialization mode; it is preferably the only AGP that may contain an ACR with the permission to delete its own AGP, as opposed to AGPs in the next tree level.

0135The third and last difference between a root ACR and a standard ACR is that it is the only ACR in the system that can have the permission to create and delete partitions.

0000SSA System ACR

0136The system ACR may be used for the following two SSA operations:

01371. Create an ACR/AGP tree under the protection of a secured channel within hostile environments.

01382. Identify and authenticate the device hosting the SSA system.

0139There may preferably be only one System ACR in the SSA and once defined it preferably cannot be changed. There is no need for system authentication when creating the System ACR; only a SSA command is needed. The create-system-ACR feature can be disabled (similarly to the create-root-AGP feature). After the system ACR is created, the create-system-ACR command has no effect, since preferably only one System ACR is allowed.

0140While in the process of creating, the System ACR is not operational. Upon finishing, a special command needs to be issued indicating that the System ACR is created and ready to go. After this point the System ACR preferably cannot be updated or replaced.

0141The System ACR creates the root ACR/AGP in the SSA. It has permission to add/change the root level until such time that the host is satisfied with it and blocks it. Blocking the root AGP essentially cuts off its connection to the system ACR and renders it temper proof. At this point no one can change/edit the root AGP and the ACRs within. This is done through an SSA command. Disabling creation of root AGPs has a permanent effect and cannot be reversed. The above features involving the system ACR are illustrated in <figref idref="DRAWINGS">FIG. 7</figref>. The system ACR is used to create three different root AGPs. At a certain time after these are created, the SSA command is sent from the host to block the root AGPs from the system ACR, thereby disabling the create-root-AGP feature, as indicated by the dotted lines connecting the System ACR to the root AGPs in <figref idref="DRAWINGS">FIG. 7</figref>. This renders the three root AGPs temper proof. The three root AGPs may be used to create children AGPs to form three separate trees, before or after the root AGPs are blocked.

0142The above described features provides great flexibility to the content owner in configuring secure products with content. Secure products need to be “Issued”. Issuance is the process of putting identification keys by which the device can identify the host and vice versa. Identifying the device (e.g. flash card) enables the host to decide whether it can trust its secrets with it. On the other hand, identifying the host enables the device to enforce security policies (grant and execute a specific host command) only if the host is allowed to.

0143Products that are designed to serve multiple applications will have several identification keys. The product can be “pre-issued”—keys stored during manufacturing before shipping, or “post issued”—new keys are added after shipping. For post issuance, the memory device (e.g. memory card) needs to contain some kind of master or device level keys which are being used to identify entities which are allowed to add applications to the device.

0144The above described features enables a product to be configured to enable/disable post issuance. In addition, the post issuance configuration can be securely done after shipping. The device may be bought as a retail product with no keys on it in addition to the master or device level keys described above, and then be configured by the new owner to either enable further post issuance applications or disable them.

0145Thus, the system ACR feature provides the capability to accomplish the above objectives:

0146Memory devices with no system ACR will allow unlimited and uncontrolled addition of applications.

0147Memory devices without system ACR can be configured to disable the system ACR creation, which means there is no way to control adding of new applications (unless the feature of creating new root AGP is disabled as well)

0148Memory devices with system ACR will allow only controlled addition of applications via a secure channel to establish through an authentication procedure using the system ACR credential.

0149Memory devices with system ACR may be configured to disable the application adding feature, before or after applications have been added.

0000Key ID List

0150Key IDs are created per specific ACR request; however, in the memory system <b>10</b>, they are used solely by the SSA system. When a key ID is created the following data is provided by or to the creating ACR:

01511. Key ID. The ID is provided by the entity through the host and is used to reference the key and data that is encrypted or decrypted using the key in all further read or write accesses.

01522. Key Cipher and data integrity Mode (the Blocked, Chained and Hashed Modes above and as explained below)

0153In addition to the host provided attributes, the following data is maintained by the SSA system:

01541. Key ID Owner. The ID of the ACR that is the owner. When a key ID is created the creator ACR is its owner. Key ID ownership may, however, be transferred to another ACR. Preferably only the key ID owner is allowed to transfer ownership of, and delegate, a key ID. Delegating access permission to the associated key, and revoking these rights can be administered either by the key ID owner or any other ACR assigned with delegation permissions. Whenever an attempt is made to exercise any one of these operations, the SSA system will grant it only if the requesting ACR is authorized.

01552. CEK. This is the CEK used to cipher the content associated with or pointed to by the key ID. The CEK may be a 128 bit AES random key generated by the SSA system.

01563. MAC and IV values. Dynamic information (message authentication codes and initiation vectors) used in the Chained Block Cipher (CBC) encryption algorithms.

0157The various features of the SSA are also illustrated in reference to the flow charts in <figref idref="DRAWINGS">FIGS. 8A-16</figref>, where ‘H’ to the left of a step means the operation is performed by the host, and ‘C’ means the operation is performed by the card. In order to create a System ACR, the host issues to the SSA in the memory device <b>10</b> a command to create System ACR (block <b>202</b>). The device <b>10</b> responds by checking whether a System ACR already exists (block <b>204</b>, diamond <b>206</b>). If it already exists, then device <b>10</b> returns failure and stops (oblong <b>208</b>). If it does not, then memory <b>10</b> checks to see if System ACR creation is allowed (diamond <b>210</b>), and returns a failure status if not allowed (block <b>212</b>). Thus, there may be instances where the device issuer does not allow the creation of a System ACR, such as in the case where the security features needed have been predetermined so that no System ACR is needed. If this is allowed, the device <b>10</b> returns OK status and waits for System ACR credentials from the host (block <b>214</b>). The host checks the SSA status and whether the device <b>10</b> has indicated that the creation of a System ACR is allowed (block <b>216</b> and diamond <b>218</b>). If creation is not allowed or if a system ACR already exists, the host stops (oblong <b>220</b>). If the device <b>10</b> has indicated that the creation of a System ACR is allowed, the host issues a SSA command to define its login credential and sends it to the device <b>10</b> (block <b>222</b>). The device <b>10</b> updates a System ACR record with the credential received and returns OK status (block <b>224</b>). In response to this status signal, the host issues SSA command indicating the system ACR is ready (block <b>226</b>). The device <b>10</b> responds by locking the System ACR so that it cannot be updated or replaced (block <b>228</b>). This locks in the features of the system ACR and its identity for identifying the device <b>10</b> to the host.

0158The procedure for creating new trees (New Root AGPs and ACR) is determined by the way these functions are configured in the device. <figref idref="DRAWINGS">FIG. 9</figref> explains the procedures. Both the host <b>24</b> and the memory system <b>10</b> follow it. If adding new root AGP is disabled altogether, new root AGPs cannot be added (diamond <b>246</b>). If it is enabled but requires a system ACR, the host authenticates through the system ACR and establishes a secure channel (diamond <b>250</b>, block <b>252</b>) prior to issuing the Create Root_AGP command (block <b>254</b>). If system ACR is not required (diamond <b>248</b>) the host <b>24</b> can issue the create root AGP command without authentication and proceed to block <b>254</b>. If system ACR does exist, the host may use it even if it is not required (not shown in the flow chart). The device (e.g. flash card) will reject any attempt to create a new root AGP if the function is disabled and it will reject an attempt to create a new root AGP without authentication, if system ACR is required (diamonds <b>246</b> and <b>250</b>). The newly created AGP and ACR in block <b>254</b>, are now switched to Operational Mode so that the ACRs in such AGPs cannot be updated or otherwise changed, and no ACRs can be added to them (block <b>256</b>). The system is then, optionally locked so that additional root AGPs cannot be created (block <b>258</b>). The dotted line box <b>258</b> is a convention indicating that this step is an optional step. All the boxes in the flow charts of the figures of this application in dotted lines are optional steps. This allows the content owner to block the use of device <b>10</b> for other illicit purposes that may imitate a genuine memory device with legitimate content.

0159To create ACRs (other than the ACRs in the root AGP as described above), one may start with any ACR that has the right to create an ACR (block <b>270</b>) as shown in <figref idref="DRAWINGS">FIG. 10</figref>. An entity may attempt to enter through the host <b>24</b> by providing the entry point ACR identity, and the ACR with all the necessary attributes that it wishes to create (block <b>272</b>). The SSA checks for a match to the ACR identity and whether the ACR with such identity has the permission to create an ACR (diamond <b>274</b>). If the request is verified to be authorized, the SSA in device <b>10</b> creates an ACR (block <b>276</b>).

0160<figref idref="DRAWINGS">FIG. 11</figref> shows two AGPs that illustrate a tree useful in security applications using the method of <figref idref="DRAWINGS">FIG. 10</figref>. Thus, the ACR with identity m<b>1</b> in the marketing AGP has the permission to create an ACR. The ACR m<b>1</b> also has the permission to use a key for reading and writing data associated with the key ID “Marketing Information” and data associated with the key ID “Price List”. Using the method of <figref idref="DRAWINGS">FIG. 10</figref>, it creates the Sales AGP with two ACRs: s<b>1</b> and s<b>2</b> with only read permission to the key for accessing pricing data associated with the key ID “Price List”, but not to the key necessary for accessing data associated with the key ID “Marketing Information”. In this manner, the entities with the ACRs s<b>1</b> and s<b>2</b> can only read but not change the pricing data, and will have no access to marketing data. The ACR m<b>2</b>, on the other hand, has no permission to create ACRs, and has only read permission to the keys for accessing data associated with the key ID “Price List” and with the key ID “Marketing Information”.

0161Thus, access rights may be delegated in the manner explained above where m<b>1</b> delegates rights to read pricing data to s<b>1</b> and s<b>2</b>. This is particularly useful where large marketing and sales groups are involved. Where there are but one or a few sales people, there may be no need to use the method of <figref idref="DRAWINGS">FIG. 10</figref>. Instead, the access rights may be delegated, by an ACR to one at a lower or the same level within the same AGP, as illustrated in <figref idref="DRAWINGS">FIG. 12</figref>. First, the entity enters the tree for such AGP by specifying an ACR in the manner described above in the tree through the host (block <b>280</b>). Next the host will specify the ACR and the rights to delegate to. The SSA checks the tree(s) for such ACR and whether the ACR has the permission to delegate rights to the specified another ACR (diamond <b>282</b>). If it does, the rights are delegated (block <b>284</b>); if not it stops. The result is illustrated in <figref idref="DRAWINGS">FIG. 13</figref>. The ACR m<b>1</b> in this case has the permission to delegate read permission to the ACR s<b>1</b>, so that s<b>1</b> will be able to use a key to access pricing data after the delegation. This may be performed if m<b>1</b> has the same or greater rights to access pricing data and the permission to so delegate. In one embodiment, m<b>1</b> retains its access rights after the delegation. Preferably access rights may be delegated under restricted conditions (rather then permanently) such as for a limited time, limited number of accesses, etc. . . .

0162The process for creating a key and key ID is illustrated in <figref idref="DRAWINGS">FIG. 14</figref>. The entity authenticates through an ACR (block <b>302</b>). The entity requests the creation of a key with an ID specified by the host (block <b>304</b>). The SSA checks and see if the ACR specified has the permission to do so (diamond <b>306</b>). For example, if the key is to be used for accessing data in a particular partition, the SSA will check and see if the ACR may access such partition. If the ACR is authorized, then the memory device <b>10</b> creates a key value associated with the key ID provided by the host (block <b>308</b>), ands stores the key ID in the ACR, and the key value in its memory (either in the controller-associated memory or memory <b>20</b>) and assigns rights and permissions according to information supplied by the entity (block <b>310</b>) and modifies the PCR of such ACR with such assigned rights and permissions (block <b>312</b>). Thus, the creator of the key has all available rights, such as read and write permissions, right to delegate and share with other ACRs in the same AGP or an ACR at a lower level, and the right to transfer ownership of the key.

0163An ACR can change the permissions (or the existence altogether) of another ACR in the SSA system as illustrated in <figref idref="DRAWINGS">FIG. 15</figref>. An entity may enter a tree through an ACR as before; in one case the entity is authenticated and then it specifies an ACR (blocks <b>330</b>, <b>332</b>). It requests the deletion of a target ACR or the permission in a target ACR (block <b>334</b>). If the ACR specified or the one active at such time has the right to do so (diamond <b>336</b>), the target ACR is deleted, or the PCR of the target ACR is altered to delete such permission (block <b>338</b>). If this is not authorized the system stops.

0164After the above described process, the target will no longer be able to access the data it was able to prior to the process. As shown in <figref idref="DRAWINGS">FIG. 16</figref>, an entity may attempt to enter at the target ACR (block <b>350</b>) and finds that the authentication process fails, since the previously existing ACR ID is no longer present in the SSA, so that access rights are denied (diamond <b>352</b>). Assuming that the ACR ID has not been deleted, the entity specifies an ACR (block <b>354</b>) and the key ID and/or data in a particular partition (block <b>356</b>), and the SSA then checks to see the key ID or partition access request is permitted according to the PCR of such ACR (diamond <b>358</b>). If the permission has been deleted or has expired, then the request is again denied. Otherwise, the request is granted (block <b>360</b>).

0165The above process describes how access to protected data is managed by the device (e.g. flash card), regardless of whether the ACR and its PCR were just changed by another ACR or were so configured to begin with.

0000Sessions

0166SSA system is designed to handle multiple users, logged in concurrently. This feature requires that every command received by the SSA is associated with a specific entity and executed only if the ACR, used to authenticate this entity, has the permissions for the requested action.

0167Multiple entities are supported through the session concept. A session is established during the authentication process and assigned a session-id by the SSA system. The session-id is internally associated with the ACR used for logging into the system and is exported to the entity to be used in all further SSA commands.

0168The SSA system supports two types of sessions: Open, and Secure sessions. The session type associated with a specific authentication process is defined in the ACR. The SSA system will enforce session establishment in a way similar to the way it enforces the authentication itself. Since the ACR defines the entity permissions, this mechanism enables system designers to associate secure tunneling either with accessing specific key IDs or invoking specific ACR management operations (i.e. creating new ACRs and setting credentials)

0000Open Session

0169Open session is a session identified with a session-id but without bus encryption, all commands and data are passed in the clear. This mode of operation is preferably used in a multi-user or multi-entity environment where the entities are not part of the threat model, nor is eavesdropping on the bus.

0170Although not protecting the transmission of the data nor enabling efficient fire-walling between the applications on the host side, the Open session mode enables the SSA system to allow access only to the information allowed for the currently authenticated ACRs.

0171The Open session can also be used for cases where a partition or a key needs to be protected. However, after a valid authentication process, access is granted to all entities on the host. The only thing the various host applications need to share, in order to get the permissions of the authenticated ACR is the session-id. This is illustrated in <figref idref="DRAWINGS">FIG. 17A</figref>. The steps above the line <b>400</b> are those taken by the host <b>24</b>. After an entity is authenticated (block <b>402</b>) for ACR<b>1</b>, it requests access to a file associated with a key ID X in the memory device <b>10</b> (blocks <b>404</b>, <b>406</b> and <b>408</b>). If the PCR of the ACR <b>1</b> allows such access, device <b>10</b> grants the request (diamond <b>410</b>). If not, the system returns to block <b>402</b>. After authentication is completed, the memory system <b>10</b> identifies the entity issuing a command only by the assigned session id (and not the ACR credentials). Once the ACR <b>1</b> gains access to the data associated with the key IDs in its PCR, in an open session, any other application or user can access the same data by specifying the correct session ID which is shared between the different applications on the host <b>24</b>. This feature is advantageous in applications where it is more convenient to the user to be able to log in only once, and be able to access all the data tied to the account through which the log in is performed for different applications. Thus, a cellular phone user may be able to access stored emails, and listen to stored music in memory <b>20</b> without having to log in multiple times. On the other hand, data not encompassed by the ACR<b>1</b> will not be accessible. Thus, the same cellular phone user may have valuable content such as games and photographs accessible through a separate account ACR<b>2</b>. This is data that he does not wish others who borrow his phone to access, even though he may not mind others accessing data available through his first account ACR<b>1</b>. Separating access to the data into two separate accounts while allowing access to ACR<b>1</b> in open session provides ease of use as well as affording protection of valuable data.

0172To even further ease the process of sharing the session-id amongst the host applications, when an ACR is requesting an Open session it can specifically request that the session will be assigned the “0 (zero)” id. This way, applications can be designed to use a pre-defined session-id. The only restriction is, for obvious reasons, that only one ACR, requesting session <b>0</b>, can be authenticated at a specific time. An attempt to authenticate another ACR requesting session <b>0</b>, will be rejected.

0000Secure Session

0173To add a layer of security, the session id may be used as shown in <figref idref="DRAWINGS">FIG. 17B</figref>. The memory <b>10</b> then also stores the session ids of the active sessions. In <figref idref="DRAWINGS">FIG. 17B</figref>, for example, in order to be able to access a file associated with key ID X, the entity will need to also provide a session id, such as session id “A” before it is allowed to access the file (blocks <b>404</b>, <b>406</b>, <b>412</b> and <b>414</b>). In this manner, unless the requesting entity is aware of the correct session id, it cannot access the memory <b>10</b>. Since the session id is deleted after the session is over and will be different for each session, an entity can gain access only when it has been able to provide the session number.

0174The SSA system has no way to make sure that a command is really coming from the correct authenticated entity, other than by using the session number. For applications and use cases where there is a threat that attackers will try to use an open channel to send malicious commands, the host application uses a secure session (a secure channel).

0175When using a secure channel, the session-id, as well as the entire command, is encrypted with the secure channel encryption (session) key and the security level is as high as the host side implementation.

0000Terminating a Session

0176A session is terminated and, the ACR is logged off, in any one of the following scenarios:

01771. The entity issues an explicit end-session command.

01782. Time out on communication. A specific entity issued no command for a time period defined as one of the ACR parameters.

01793. All open sessions are terminated after device (e.g. flash card) reset and/or power cycle.

0000Data Integrity Services

0180The SSA system verifies the integrity of the SSA database (which contains all the ACRs, PCRs, etc . . . ). In addition data integrity services are offered for entity data through the key ID mechanism.

0181If a key ID is configured with Hashed as its encryption algorithms the hash values are stored along side with the CEK and IV in the CEK record. Hash values are calculated and stored during write operation. Hash values are again calculated during read operations and compared with the values stored during the previous write operations. Every time the entity is accessing the key ID the additional data is concatenated (cryptographically) to the old data and the appropriate Hash value (for read or for write) updated.

0182Since only the host knows the data files associated with or pointed to by a key ID, the host explicitly manages several aspects of the data integrity function in the following manner:

01831. A data file associated with or pointed to by a key ID is written or read from the beginning to end. Any attempt to access portions of the file will mess it up since the SSA system is using a CBC encryption method and generates a hashed message digest of the entire data

01842. There is no need to process the data in a contiguous stream (the data stream can be interleaved with data streams of other key Ids and may be split over multiple sessions) since intermediate Hash values are maintained by the SSA system. However, the entity will need to explicitly instruct the SSA system to reset the Hash values if the data stream is restarted.

01853. When a read operation is completed, the host must explicitly request the SSA system to validate the read Hash by comparing it with the Hash value calculated during the write operation.

01864. The SSA system provides a “dummy read” operation as well. This feature will stream the data through the encryption engines but will not send it out to the host. This feature can be used to verify data integrity before it is actually read out of the device (e.g. flash card).

0000Random Number Generation

0187The SSA system will enable external entities to make use of the internal random number generator and request random numbers to be used outside of the SSA system. This service is available to any host and does not require authentication.

0000RSA Key Pair Generation

0188The SSA system will enable external users to make use of the internal RSA key pair generation feature and request an RSA key pair to be used outside of the SSA system. This service is available to any host and does not require authentication.

Alternative Embodiment

0189Instead of using a hierarchical approach, similar results can be achieved using a data base approach, as illustrated in <figref idref="DRAWINGS">FIG. 18</figref>.

0190As shown in <figref idref="DRAWINGS">FIG. 18</figref>, a list of credentials for entities, authentication methods, the maximum number of failed attempts, and the minimum number of credentials needed to unblock may be entered into a database stored in controller <b>12</b> or memory <b>20</b>, which relates such credential requirements to the policies (read, write access to keys and partitions, secure channel requirement) in the database carried out by the controller <b>12</b> of memory <b>10</b>. Also stored in the database are constraints and limitations to the access to keys and partitions. Thus, some entities (e.g. system administrator) may be on a white list, which means that these entities can always access all keys and partitions. Other entities may be on a black list, and their attempts to access any information will be blocked. The limitation can be global, or key and/or partition specific. This means that only certain entities can always access certain specific keys and partitions, and certain entities always cannot do so. Constraints can also be put on the content itself, irrespective of the partition it is in or the key used to encrypt or decrypt it. Thus, certain data (e.g. songs) may have the attribute that they can only be accessed by the first five host devices that access them, or that other data (e.g. movies) can only be read for a limited number of times, irrespective of which entities had access.

0000Authentication

0191Password Protection

0192Password-protect means that a password needs to be presented to access the protected area. Unless it cannot be more than one password then passwords could be associated with different rights such as read access or read/write access.

0193Password protect means that the device (e.g. flash card) is able to verify a password provided by the host i.e. the device also has the password stored in device managed secured memory area.

0194Issues and Limitations

0195Passwords are subject to replay attack. Because the password does not change after each presentation it can be identically resent. It means that password as is must not be use if the data to be protected are valuable, and the communication bus is easily accessible.

0196Password could protect access to stored data but should NOT be used to protect data (not a key)

0197To increase the security level associated with passwords, they can be diversified using a master key, with the result that hacking one does not crack entire system. A session key based secure communication channel can be use to send the password.

0198<figref idref="DRAWINGS">FIG. 19</figref> is a flow chart illustrating authentication using a password. The entity sends in an account id and password to system <b>10</b> (e.g. flash memory card). The system checks to see if the password matches that in its memory. If it matches, authenticated status is returned. Otherwise, the error counter is incremented for that account, and the entity is asked to re-enter an account id and password. If the counter overflows, the system return status that access is denied.

0199Challenge Response

0200<figref idref="DRAWINGS">FIG. 20</figref> is a Flow Chart illustrating authentication using a challenge/response type method. The entity sends in an account id and requests a challenge from system <b>10</b>. System <b>10</b> generates a random number and presents it to the host. The host computes a response from the number and sends it to the system <b>10</b>. System <b>10</b> compares the response to the value stored. The remaining steps are similar to those in <figref idref="DRAWINGS">FIG. 19</figref> for determining whether to grant access.

0201<figref idref="DRAWINGS">FIG. 21</figref> is a Flow Chart illustrating authentication using another challenge/response type method. <figref idref="DRAWINGS">FIG. 21</figref> differs from that in <figref idref="DRAWINGS">FIG. 20</figref> in that, in addition to requiring the host to be authenticated by the system <b>10</b>, it also requires the system <b>10</b> to be authenticated by a challenge/response where system <b>10</b> also requests a challenge from the host and returns a response to be checked by the host.

0202<figref idref="DRAWINGS">FIG. 22</figref> is a Flow Chart illustrating authentication using another challenge/response type method. In this case, only the system <b>10</b> needs to be authenticated, where the host sends a challenge to system <b>10</b>, which computes a response that is checked by the host for a match with its record of system <b>10</b>.

0203Symmetric Key

0204Symmetric key algorithm means that the SAME key is used on both sides to encrypt and decrypt. It means that the key must have been pre-agreed prior to communicating. Also each side should implement the reverse algorithm of each other i.e. encrypt algorithm on one side and decrypt on the other. Both sides do not need to implement both algorithms to communicate.

0205Authentication

0206Symmetric key authentication means that device (e.g. flash card) and host share the same key and have the same cryptographic algorithm (direct and reverse e.g. DES and DES-<b>1</b>).

0207Symmetric key authentication means challenge-response (protect against replay attack). The protected device generates a challenge for the other device and both compute the response. The authenticating device sends back the response and the protected device check the response and validate authentication accordingly. Then rights associated with authentication can be granted.

0208Authentication could be:

0209External: the device (e.g. flash card) authenticates the outside world i.e. the device validates credentials of a given host or application

0210Mutual: a challenge is generated on both sides

0211Internal: the host application authenticates the device (e.g. flash card) i.e. host checks if device is genuine for its application.

0212To increase the security level of the entire system (i.e. breaking one does not break all)

0213Symmetric key are usually combined with diversification using a master key

0214Mutual authentication uses challenge from both side to ensure challenge is a real challenge

0215Encryption

0216Symmetric key cryptography is also used for encryption because it is a very efficient algorithm i.e. it does not need a powerful CPU to handle cryptography.

0217When used to secure a communication channel:

0218Both devices have to know the session key used to secure the channel (i.e. encrypt all outgoing data and decrypt all incoming data). This session key is usually established using a pre-shared secret symmetric key or using PKI.

0219Both devices have to know and implement the same cryptographic algorithms Signature

0220Symmetric key can also be used to sign data. In that case the signature is a partial result of the encryption. Keeping the result partial allows to sign as many time as needed without exposing the key value.

0221Issues and Limitations

0222Symmetric algorithms are very efficient and secure but they are based on a pre-shared secret. The issue is securely share this secret in a dynamic manner and possibly to have it random (like a session key). The idea is that a shared secret is hard to keep safe in a long term and is almost impossible to share with multiple people.

0223To facilitate this operation, public key algorithm has-been invented as it allows the exchange of secrets without sharing them.

0224Public Key Cryptography

0225Asymmetric key algorithm is commonly referred Public Key cryptograph. It is a quite complex and usually CPU intensive mathematical implementation. It has been invented to solve the issues of key distribution associated with symmetric key algorithms. It also provides signing capabilities used to ensure data integrity.

0226Asymmetric key algorithm uses a key which has private and public elements respectively referred as private key and public key. Both private key and public key are mathematically linked together. The public key can be shared whereas the private has to remain secret. As for the keys, asymmetric algorithm uses two mathematical functions (one for the private key and one for the public key) to provide wrap and unwrap or sign and verify.

0227Key Exchange and Key Distribution

0228Key exchange becomes very simple using PK algorithm. The device sends its public key to the other device. The other device wraps its secret key with the public key and returns the encrypted data to the first device. The first device uses its private key to unwrap the data and retrieve the secret key which is now known to both sides and can be used to exchange data. Because the symmetric key can be exchanged that easily it is usually a random key.

0229Signature

0230Because of its nature public key algorithm is usually used only to sign small amount of data. To ensure data integrity it is then combine with a hash function that provides a one-way foot print of the message.

0231The Private key is used to sign the data. The public key (freely available) allows to verify the signature.

0232Authentication

0233Authentication usually uses signature: a challenge is signed and returned for validation

0234The public part of the key is used for verification. Because anyone can generate a key pair, there is a need to certify the owner of the public key in order to prove that this is the right person using the correct key. Certification authority provides certification and will include the public key in a signed certificate. The certificate is signed by the authority itself. Then using a public key to verify a signature means that the authority that issued the certificate containing that key is trusted and that one is able to verify that the certificate has not been hacked i.e. that the certificate hash signed by the authority is correct; meaning that the user has and trusts the authority public key certificate.

0235The most common way to provide PK authentication is to trust the authority or root certificate and indirectly trust all key pairs certified by the given authority. Authenticating is then a matter of proving that the private key that one has matches the certificate by signing a challenge and providing the challenge response, and the certificate. Then certificate is checked to make sure it has not been hacked and it is signed by a trusted authority. Then the challenge response is verified. Authentication is successful if the certificate is trusted and the challenge response is correct.

0236Authentication in a device (e.g. flash card) means that the device is loaded with trusted root certificates and that the device is able to verify the challenge response as well as the certificate signed hash.

0237File Encryption

0238PK algorithm is not used to encrypt large amounts of data because it is too CPU intensive, but is usually used to protect a randomized encryption/decryption key generated to encrypt the content. For example SMIME (Secure email) generate a key which is then encrypted with all recipients' public key.

0239Issues and Limitations

0240Because anything can generate a key pair, it has to be certified to ensure its origin. During key exchange one may want to make sure that the secret key is provided to the right device i.e. the origin of the provided public key will need to be checked. Certificate management then becomes part of the security as it can inform about the validity of the key, and whether the key has been revoked.

0241While the invention has been described above by reference to various embodiments, it will be understood that changes and modifications may be made without departing from the scope of the invention, which is to be defined only by the appended claims and their equivalent. All references referred to herein are incorporated by reference.