System and method for enhanced piracy protection in a wireless personal communication device

FIELD OF THE INVENTION

[0001] The present invention pertains to portable communication devices, and in particular, portable communication devices suitable for playing video and audio content which accommodate a removable user interface module, and more particularly to piracy protection in portable communication devices using split-key cryptography.

BACKGROUND OF THE INVENTION

[0002] Electronic devices are known which operate with a portable, removable user module or card having, for example, an integral microprocessor, a memory element, or both. Examples of such electronic devices include automated teller machines (ATM), pagers, personal digital assistants (PDA), and radiotelephones, such as cellular, wireless and cordless telephones. Examples of removable user modules include a subscriber identity module (SIM) which is used in portable telephones to communicate with a base station under specifications such as the Global System for Mobile Communication (GSM) specification.

[0003] With increased processing capability, improved audio and visual capability and expanded memory capability, users of portable devices have an increasing desire to download and view movies or music over wireless channels for playing on these portable devices. Because the content is typically stored and transmitted in a digital form, there is a substantial increased risk that the content may be illicitly intercepted, copied and redistributed for illegal gain. Unlike typical analog versions of video and music content, piracy of the digital form results in a very high quality reproduction of the content. Therefore, controlling unauthorized use of digital content is highly desirable.

[0004] Various cryptographic systems and techniques have been developed for securing content transmitted across a non-secure communications channel, however, these techniques are generally not suitable for controlling content when control of content's use is sought by several independent or distant entities. For example, a content provider may prefer that content be accessible by a user only when the user has sufficient credit to pay for the content use, while at the same time, the content provider desires to limit usage of the content to an authorized user.

[0005] Thus what is needed is a method and apparatus for reducing the risk of piracy when distributing and playing content. What is also needed is a method and apparatus that allows several entities to have control of content use and distribution.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The invention is pointed out with particularity in the appended claims. However, a more complete understanding of the present invention may be derived by referring to the detailed description and claims when considered in connection with the figures, wherein like reference numbers refer to similar items throughout the figures and:

[0007]FIG. 1 illustrates a simplified functional block diagram of a system configuration for piracy protection for in accordance with an embodiment of the present invention;

[0008]FIG. 2 illustrates a simplified functional block diagram of a portable communication device in accordance with an embodiment of the present invention;

[0009]FIG. 3 illustrates a simplified flow chart of a key generation and distribution procedure in accordance with an embodiment of the present invention; and

[0010]FIG. 4 illustrates a simplified flow chart of a content request and usage procedure in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

[0011] The present invention provides, among other things, a method and system for the secure delivery and use of content in a personal communication device using a split key, key-sharing scheme. In accordance with one of the embodiments, a private key is split into key-shares using a key splitting technique, such as a Blakley-Shamir key splitting technique, and the key-shares are distributed to various network entities including a finance server and security server. Key-shares are also stored in a user's subscriber identity module (SIM) and a security processor of the personal communication device. The key-shares from the network entities are provided to the personal communication device after the user requests specific video or audio content and a credit verification is performed. The personal communication device combines the key-shares to form the decryption key for use in playing the content. When a service limit is reached, the personal communication device purges the key-shares to prevent further use of the content.

[0012] Cryptosystems have been developed for maintaining the privacy of information transmitted across a communications channel. Symmetric cryptosystems have been used for this purpose. Symmetric cryptosystems utilize a single electronic key for decryption and encryption, and can be likened to a physical security system where a box has a single locking mechanism with a single key hole. One key holder uses the key to open the box, place a message in the box and relock the box. Only a second holder of the identical copy of the key can unlock the box and retrieve the message. The term symmetric reflects the fact that both users have identical keys. The details of the enciphering and deciphering functions of a symmetric cryptosystem are well known, and the security of the system depends solely on maintaining the secrecy of the key. Conventional symmetric cryptosystems are fairly efficient and can be used for encryption at fairly high data rates, especially if appropriate hardware implementations are used.

[0013] Asymmetric cryptosystems, often referred to as public key cryptosystems, provide another means of encrypting information. Asymmetric cryptosystems differ from symmetric systems by providing separate keys for encryption and decryption.

[0014] In public key electronic cryptosystems, each entity, has a private key which is known only to the entity, and a public key which is publicly known. Once a message is encrypted with a user's public-key, it can only be decrypted using that user's private-key, and conversely, if a message is encrypted with a user's private-key, it can only be decrypted using that user's public-key. One problem with the use of both symmetric and asymmetric cryptographic techniques is that it is difficult for several entities to control content distribution.

[0015] Blakley, in an article entitled, “Safeguarding cryptographic keys”, in AFIPS-Conference Proceedings, 48:313-317, June 1979, and Shamir in an article entitled “How to share a secret” in Communications of the ACM, 22(11):612-613, 1979, describe methods where a secret cryptographic key is shared among one or more trustees. In particular, each trustee is given a secret piece of the secret key for each user. The sharing of a key satisfies two properties. First, no subset of the trustees should be able to pool their knowledge in order to figure out the secret key of a user. Second, any set of trustees greater than a certain number should be able to recover the secret key of a user by pooling their shares of that key. Many such “secret sharing” schemes are known in the literature (e.g., see the survey paper by G. Simmons entitled “How to really share a secret”, Crypto 90, pages 390-448, August 1990).

[0016] In accordance with one of the embodiments, the present invention implements a key-splitting key-sharing scheme to control distribution and use of content in a personal communication device. FIG. 1 illustrates a simplified functional block diagram of a system configuration for piracy protection in accordance with an embodiment of the present invention. System <b>100</b> includes security server <b>102</b> including key share <b>103</b>, content server <b>104</b> and finance server <b>106</b> coupled to network <b>110</b>. System <b>100</b> also includes interface element <b>114</b> that provides for communications between network <b>110</b> and wireless communication devices such as Personal Communication Device (PCD) <b>108</b> over wireless links such as wireless link <b>112</b>. In accordance with one embodiment of the present invention, interface element <b>114</b> may provide a wide area network (WAN) type interface to PCD <b>108</b>. Service provider <b>101</b> provides communication services for personal communication device <b>108</b>.

[0017] Desirably, service provider <b>101</b>, security server <b>102</b>, content server <b>104</b> and finance server <b>106</b> communicate with each other and with personal communication device <b>108</b> through network <b>110</b>, which may be any communication network and is desirably an internet type network that provides packetized digital communications. In an alternate embodiment of the present invention, some communications between service provider <b>101</b>, security server <b>102</b>, content server <b>104</b> and finance server <b>106</b> may take place over communication channels (not shown) outside of network <b>110</b>. Virtual private network (VPN) communication may also be implemented. As discussed in more detail below, in some cases it is desirable for certain communications between service provider <b>101</b>, security server <b>102</b>, content server <b>104</b> and finance server <b>106</b> to be secured, and therefore desirable to implement a secure communication path through network <b>110</b> or a separate secure channel outside of network <b>110</b>.

[0018] Although service provider <b>101</b>, security server <b>102</b>, content server <b>104</b> and finance server <b>106</b> are illustrated as separate functional elements of system <b>100</b> for ease of understanding, it should be understood that service provider <b>101</b>, security server <b>102</b>, content server <b>104</b> and finance server <b>106</b> may each be implemented as separate physical components, for example, located at different geographic locations. Alternatively, service provider <b>101</b>, security server <b>102</b>, content server <b>104</b> and finance server <b>106</b> may be implemented as one physical component with the different functional elements residing at a single geographic location.

[0019] Content server <b>104</b> desirably operates in conjunction with a content provider that has access to video content and audio content which a user may desire to view or listen to for a fee. Video content, for example, may include movies, archived television shows, music videos, etc. Audio content, for example, may include music, audio books, etc. Content, as used herein also includes any digital information including software which may be desired to be secured and have its use controlled. Content server <b>104</b> provides for the storage of content and the communication of content with security server <b>102</b>. Desirably, content server <b>104</b> implements a secure method of communicating content with security server <b>102</b>, and may implement a symmetric or asymmetric encryption technique with security server <b>102</b> for securing the content, or may communicate content with security server <b>102</b> over a secure or dedicated communication channel (not shown).

[0020] Security server <b>102</b> provides for the security involved by providing content services for a user of personal communication device <b>108</b>. Security server <b>102</b>, among other things, generates encryption keys, encrypts content with an encryption key, and provides for authentication of communications. Security server <b>102</b> also splits decryption keys to generate key-shares as described below. Security server <b>102</b> desirably provides the secured content to personal communication device <b>108</b> along with key-share <b>103</b> which is used in part to decrypt the encrypted content. In one embodiment, service provider <b>101</b> uses security server <b>102</b> as its front-end device for building and controlling keys for control of the content.

[0021] In one of the embodiments, encryption keys and associated key-shares are associated with an individual user, however this is not a requirement. In this embodiment, a user's public key (or other known public key) may be used to encrypt content and an associated private key is divided into key-shares and used for decryption. Desirably, security server <b>102</b> implements a Blakley-Shamir key-splitting technique, however other known key-splitting and shared-secret techniques are also applicable to the present invention. In another embodiment, encryption keys are associated with the content.

[0022] Finance server <b>106</b> provides for the verification of credit for a user based on a user's request for content usage services. For example, when a user requests to download a movie on his personal communication device, finance server <b>106</b> verifies the user has established an applicable credit limit and will debit the user's account. In this example, the finance server <b>106</b> may have been provided a credit card number for the user. The finance server <b>106</b>, for example, verifies the credit card is valid, verifies that the credit card has sufficient credit, and charges the credit card accordingly. Security server <b>102</b> and/or service provider <b>101</b> provide information to finance server <b>106</b> so that it can identify the user along with an amount of credit for the requested service. Desirably, communications with finance server <b>106</b> are at least authenticated using digital signature technology and may also be encrypted. In one of the embodiments, key-share <b>107</b> is held for finance server <b>106</b> by the security server <b>102</b>, and provided to the finance server <b>106</b> as described below. Key-share <b>107</b> is one of the key-shares that security server <b>102</b> generated by splitting a decryption key which is used in part to decrypt the encrypted content. Key-share <b>107</b> is desirably provided to finance server <b>106</b> after a user request for content is received as part of the finance credit verification. In an alternate embodiment, key-share <b>107</b> is stored in finance server <b>106</b> prior to a credit verification request.

[0023] Personal communication device (PCD) <b>108</b> is a communication device configured to, among other things, receive video and/or audio content and play the content for a user in accordance with security requirements discussed herein. Although only a single personal communication device <b>108</b> is shown, the present invention contemplates that many thousands of personal communication devices operate in system <b>100</b>. The system, according to embodiments of the invention, can be advantageously applied to personal digital assistants (PDAs), mobile communication devices, portable computers and multipurpose communication devices. A multipurpose communication device here refers to a portable device that can be used for communication in many ways (e.g., wireless internet communications, as a wireless telephone communications, computer terminal, etc.). In accordance with one of the embodiments of the present invention, personal communication device <b>108</b> is a PDA with suitable interfaces and sufficient memory and processing power for playing video and audio, and implementing the procedures described herein.

[0024]FIG. 2 illustrates a simplified functional block diagram of portable communication device in accordance with an embodiment of the present invention. Personal communication device <b>108</b> includes processor area <b>202</b>, an area for receiving a subscriber identification module (SIM) <b>210</b>, other component (OC) area <b>212</b> and RF interface <b>214</b>. Processor area <b>202</b> is comprised of several functional processing elements (e.g., portions)and includes, among other things, security processor <b>204</b>, applications processor <b>206</b>, communications processor <b>208</b>, and other components associated therewith including memory. Although security processor <b>204</b>, applications processor <b>206</b> and communications processor <b>208</b> are illustrated as separate functional components, security processor <b>204</b>, applications processor <b>206</b> and communications processor <b>208</b> may alternatively be implemented as one or more processing elements. Desirably, security processor <b>204</b>, applications processor <b>206</b> and communications processor <b>208</b> are fabricated as an application specific integrated type circuit, however this is not a requirement. In accordance with one embodiment, security processor <b>204</b> includes key-share <b>205</b>. Key-share <b>205</b> is one of the key-shares that security server <b>102</b> generated by splitting a decryption key which is used in part to decrypt the encrypted content. Key-share <b>205</b> is desirably provided to personal communication device as part of a transaction with security server <b>102</b>.

[0025] The SIM <b>210</b> is a subscriber identification module (SIM) or card which includes, among other things, user identification information including, for example, a user's token which may include the user's private key. Desirably, user information stored in SIM <b>210</b> is secured. SIM <b>210</b> also includes key-share <b>211</b> which is one of the key-shares that security server <b>102</b> generated by splitting a decryption key which is used in part to decrypt the encrypted content. Key-share <b>211</b> may be stored in SIM <b>210</b> by content server <b>104</b> (FIG. 1) or alternatively, content server <b>104</b> may provide SIM <b>210</b> to a user with key-share <b>211</b> already stored thereon.

[0026] Personal communication device <b>108</b> also includes an other component area <b>212</b>. Other component area <b>212</b> includes components such as I/O, keypad, display, speakers, memory, ports, etc., which in addition to the elements described herein, comprise personal communication devices. For example, when personal communication device <b>108</b> includes the functionality of a wireless telephone, components necessary for the operation of wireless telephone are included in area <b>212</b>. In accordance with one of the embodiments, personal communication device <b>108</b> is a wireless communication device and includes RF interface <b>214</b> for communicating over a wireless link to a network connection or communication system which may include the internet, a wireless telephone system and/or other digital communication network.

[0027]FIG. 3 illustrates a simplified flow chart of a key generation and distribution procedure in accordance with an embodiment of the present invention. Procedure <b>300</b> is desirably implemented by system elements and configuration illustrated in FIG. 1, however this is not a requirement. In block <b>302</b>, an encryption key for encrypting content is generated or obtained. Key generation may be accomplished by many techniques known to those of skill in the art, however encryption keys with corresponding decryption keys suitable for key-splitting in accordance with the present invention are desirable. In one embodiment of the present invention, the keys may be pre-generated, for example, by a third party, and stored in the security server for use at a subsequent time.

[0028] In block <b>304</b>, content is encrypted with the encryption key generated or obtained in block <b>302</b>. Referring to FIG. 1, content is desirably encrypted by the security server when the security server is provided “plain-text” content from content provider. In another embodiment, a content provider performs the encryption, in which case the encryption key is provided by the security server to the content server. Upon the completion of block <b>304</b>, encrypted content is available for being provided to users.

[0029] In block <b>306</b>, the appropriate decryption key is split into a plurality of key-shares. An n-way split may be implemented where “n” is desirably either 2, 3 or 4, although greater values for “n” are also acceptable. Block <b>306</b> is desirably performed by the security server and may be performed as part of block <b>302</b>. In block <b>308</b>, a first of the key-shares is retained on the security server.

[0030] In block <b>310</b>, a second of the key-shares is transferred to and stored on a SIM that is provided to a user. Desirably, the content provider performs this block, however it may be performed by the security server. In one embodiment, a user may obtain a SIM from a content provider, or alternatively, the user may provide the user's SIM to the content provider for configuration and storage of the key-share.

[0031] In one of embodiments, the security server holds a third key-share which resulted from block <b>306</b>. In this embodiment, this third key-share is intended for use by the finance server. In block <b>312</b>, the third key-share is held by the security server for the finance server until a credit verification process when the third key-share is provided to the finance server. The credit verification process is performed prior to the security server providing encrypted content to a user.

[0032] In block <b>314</b>, when “n” is four, a fourth key-share which resulted from block <b>306</b>, is placed on the security processor of a personal communication device. Block <b>314</b> may be performed when a user inserts a SIM into the personal communication device, and is desirably initiated automatically in a transaction between the personal communication device and the security server. The fourth key-share, which is transferred over the network and wireless link to the personal communication device, is desirably secured by a security method such as PGP's transport layer security (TSL) method.

[0033] Upon the completion of procedure <b>300</b>, key-shares are distributed in various network elements and elements of a user's device. For example, when a key is split four ways, a first key-share resides in the security server, a second key-share resides in a user's SIM, a third key-share is held for a finance server, and a fourth key-share resides in the security processor of the user's personal communication device. Other embodiments of the present invention contemplate splitting a key two or three ways and accordingly, key-shares do not reside in all the network or user device elements previously mentioned. In yet other embodiments of the present invention, key-shares may also be placed in the communication processor and/or application processor of a personal communication device for further enhancement of security.

[0034]FIG. 4 illustrates a simplified flow chart of content request and usage procedure in accordance with an embodiment of the present invention. Procedure <b>400</b> is desirably implemented by system elements and configuration illustrated in FIG. 1, however this is not a requirement. In accordance with one of the embodiments, portions of procedure <b>300</b> (FIG. 3) may be performed concurrently with portions of procedure <b>400</b>, however, procedure <b>300</b> (FIG. 3) may be performed prior to procedure <b>400</b> depending on the type of key-splitting and encryption processes implemented.

[0035] In block <b>402</b>, a set of measurement parameters is obtained. The measurement parameters define restrictions placed on a user's use of content. The measurement parameters desirably comprise at least one of a date limit, a run-time limit, an iteration limit, an on-demand service in real-time limit, a run-time and iteration combination limit, and a run-time and time of day combination limit, although other combinations and other measurement parameters are equally suitable for use with the various embodiments of the present invention. For example, the measurement parameters may define a service limit that allows a user to play content an unlimited number of times over a week period. For example, the set of measurement parameters may allow a user to play the complete content a predetermined number of times without a time period restriction. For example, a set of measurement parameters may allow a user to play content for a predetermined number of minutes, which for example would allow the user to repeatedly play certain portions of the content up until a play time limit is reached. A measurement parameter may also be included to indicate whether the content will be used commercially or privately.

[0036] In one embodiment of the present invention, the set of measurement parameters are generated by a user based on the user's intended usage of the content. In this case, the user desirably negotiates the measurement parameters with the content provider and possibly a finance organization or agency.

[0037] In alternate embodiments, the content provider provides a selection of various sets of measurement parameters and their associated costs. The user selects a desired set that meets the user's needs. For example, the content provider may advertise a rate for movies that are restricted to a one-time play, and another rate for movies that are restricted to a predetermined day use period. The finance server may verify the user's credit as part of block <b>402</b>, or may verify the user's credit when specific content is requested.

[0038] The measurement parameters may be secured with an authentication code to prevent tampering therewith. The authentication code may be added by the security server.

[0039] In block <b>404</b>, the user sends a request for specific content to the security server. The request desirably includes the set of measurement parameters, however this is not a requirement. The measurement parameters may be determined subsequent to requesting content. In other words, block <b>402</b> and <b>404</b> may be performed concurrently or in any order.

[0040] In response to the user request for content, block <b>408</b> is performed. In block <b>408</b>, the key-share which is stored in the security server associated with the requested content is identified. Desirably, the request message from the user is parsed to identify the key-share.

[0041] In block <b>410</b>, the security server communicates with the finance server providing information about the measurement parameters and content desired by the user. In one embodiment, the security server may provide the cost associated with the content service requested, however in an alternative embodiment, the finance server may communicate with the content server to determine a cost associated with the user's requested content service.

[0042] In block <b>412</b>, the finance server verifies the user's credit based on the requested content service requested in block <b>410</b>. When the user has sufficient credit to cover the cost of the requested service, the finance server accesses one of the key-shares (i.e., the third key-share) in accordance with the information provided by the security server in block <b>410</b>. Desirably, the finance server debits or charges the user's account accordingly. This third key-share is used to verify that the user has sufficient credit and has paid for the requested content service.

[0043] In accordance with one of the embodiments, the security server provides either the third key-share or an index identifying where the finance server can obtain the third key-share. The third key-share is desirably held by the security server (see block <b>312</b> of procedure <b>300</b> FIG. 3) until completion of block <b>412</b>.

[0044] In block <b>414</b>, the finance server sends the third key-share to the user's personal communication device in response to credit verification of block <b>412</b>. As part of this block, the security server may also send the first key-share that the security server was retaining to the user's personal communication device, however, the security server may send the first key-share to the user's personal communication device at an earlier time. Various security techniques may be employed for sending keys shares over a non-secured network. The first and third key-shares are stored in a storage element of the user's personal communication device.

[0045] In block <b>416</b>, the encrypted content is transferred to the user's personal communication device from the security server, or alternatively, from the content provider depending on the embodiment. Desirably, the finance server notifies the security server that it has approved the user's credit and, in response, the security server performs block <b>416</b>. The encrypted content is stored in a storage element of the user's personal communication device. Desirably, the communication processor of the personal communication device receives the encrypted content.

[0046] In block <b>418</b>, in response to an input from the user to play the requested content, the user's personal communication device combines the first, second, third and fourth key-shares to obtain a decryption key for the content. This allows the personal communication device to decrypt and play the content. In accordance with one of the embodiments, the user's personal communication device has a processor area comprised of a security processor which stores the fourth key-share and a functionally separate communication processor and applications processor such as illustrated in FIG. 1. In this embodiment, the first and third key-shares are transferred to the security processor, the second key-share is collected from the SIM based on a key-share index and transferred to the security processor and combined with the first key-share in the security processor. The key share index allows operators, such as the content providers to better control content. For example, a set of key-shares may be placed in the SIM and the negotiation for service may allow the service provider to differentiate various types of usage within one account.

[0047] In block <b>420</b>, the security processor of the personal communication device decrypts the content and the communication processor plays the decrypted content. In addition, the security processor performs a process that monitors content usage in relation to the measurement parameters to determine when a service limit is reached. Security measures within the processing area of the personal communication device prevent the storage of decrypted content.

[0048] In block <b>422</b>, when the security processor determines that a service limit is reached for playing the content, the security processor purges at least one of the key-shares (and desirably the entire decryption key) from its registers and memory to prevent further use of the content. When an authentication code is included with the measurement parameters, the security processor may purge the decryption key or one of the key-shares at any time the authentication code fails to authenticate. This prevents tampering with the measurement parameters.

[0049] In one embodiment of the present invention, when the user desires to continue playing the content, a second decryption key may be generated and split into shares and provided to the user in accordance with the processes described herein.

[0050] Although the present invention is described in accordance with one of the embodiments using encryption and decryption to control re-playing of content, in another embodiment, content may be controlled through the use of digital certificate checking.

[0051] Thus, a method and system for piracy protection in a personal communication device has been described which overcomes specific problems and accomplishes certain advantages relative to prior art methods and systems. The playing of content, such as video and music, is controlled through the use of split decryption keys which gives content providers additional assurance that the content will not be misused.

[0052] The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and therefore such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments.

[0053] It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Accordingly, the invention is intended to embrace all such alternatives, modifications, equivalents and variations as fall within the spirit and broad scope of the appended claims.