Authentification of a user across communicaqtion sessions

ES 2 279 871 T3

DESCRIPTION

Authentication of a user through communication sessions.

Field of the invention

The invention relates to the field of client-server communications, and more specifically to a method and apparatus to facilitate the re-authentication of a user using a client computer, against a server computer. Background of the invention

A user typically provides authentication credentials, such as a login password, to a server computer at the start of, or during, a communication session. The server computer typically maintains a centralized storage area, in the server computer's memory, for storing the authentication credentials, which are typically encrypted in some way. The server computer may then verify the received authentication credentials from the user against the encrypted authentication credentials stored in the server's memory to authorize the user's access to the server computer.

If an established communication session between the user and the server ends abnormally, the user generally has to reestablish the connection by starting a new communication session. To start a new communication session, the user typically has to relay the authentication credentials (eg, login password) to the server computer, so that the server computer can authorize the user for a new communication session. This retransmission of the authentication credentials of a user, through multiple communication sessions, repeatedly exposes the authentication credentials of that user, to potential attackers, thereby lowering the security level of the authentication credentials. Thus, it is desirable to provide a technique for reestablishing a communication session between a client computer and a server computer, without repeatedly transmitting authentication credentials.

Summary of the invention

Document US-A-5 058 480 refers to a system and a method for authenticating users and services communicating over an insecure network, and reveals characteristics of the pre-characterizing part of the independent claim.

The invention is set forth in the characterizing part of independent claims 1 and 13. Furthermore, optional features are set forth in the dependent claims.

The invention relates to an apparatus and a method for eliminating the retransmission of the authentication credentials of a single user, after the termination of a previous communication session. To eliminate retransmission, a server computer encrypts the authentication credentials with a key, and associates the encrypted authentication credentials with a session identifier (SID). The SID identifies the current communication session. The server computer then transmits the encryption key and SID to the client, and then clears the key from the server's memory. Thus, the web server computer can only decrypt the encrypted authentication credentials, when the server computer receives the SID and key from the client. The server computer uses the SID to locate the correct key, and then uses the key to decrypt the encrypted authentication credentials.

In one embodiment, the invention relates to a method of facilitating re-authentication of a client on a server computer. In one embodiment, the method includes the steps of receiving, from the server computer, authentication credentials at the beginning of, or during, a first communication session between the server and the client, and encrypting the authentication credentials with a key to create encrypted authentication credentials. The server computer then creates a session identifier (SID) to identify the communication session, and stores the encrypted authentication credentials and the SID in the server computer's memory. The method further includes the steps of transmitting the key and SID to the client, and then erasing the key from the server's memory. When the server computer receives the key and SID from the client during a communication session, the server computer uses the SID to locate the correct encrypted authentication credentials, and then uses the key to decrypt the encrypted authentication credentials.

The invention also relates to a system to facilitate the re-authentication of a client on a server computer. The server computer includes a memory, a key generator, a SID generator, a key destroyer, and an encryption device. The server computer receives authentication credentials from the client computer. Then the key generator generates a key and the SID generator generates a SID, for the communication session. The encryption device then encrypts the authentication credentials with the key, to create the encrypted authentication credentials. The encryption device then stores the encrypted authentication credentials and the SID, in the server's memory. The server computer then transmits the key and SID to the client computer. The key destroyer then clears the key from the server computer's memory, after transmitting the key to the client.

The server computer also includes a decryption device. When the server computer receives a key and the SID from the client, at the start of, or during, a second communication session, the server computer

ES 2 279 871 T3 uses the SID to locate the encrypted authentication credentials associated with the user. The decryption device then decrypts the encrypted authentication credentials, using the key received from the client, and re-authenticates the user.

Brief description of the drawings

The invention is set forth with particularity in the appended claims. The drawings are not necessarily to scale, instead the emphasis is generally placed on illustration of the principles of the invention. The same reference characters in the respective figures of the drawings indicate corresponding parts. The advantages of the invention can be better understood with reference to the following description, taken in conjunction with the accompanying drawings, in which:

Figure 1 is a block diagram of an embodiment of a computer system for maintaining authentication credentials, in accordance with the invention;

Figure 2A is a diagram of the steps followed in an embodiment of the computer system of Figure 1, to maintain authentication credentials during a first communication session, in accordance with the invention; and Figure 2B is a flow chart of the steps followed in one embodiment of the computer system of Figure 1, to maintain authentication credentials during a second communication session, followed by the termination of the first communication session of Figure 2A, according to the invention.

Description of the preferred embodiment

With reference to Figure 1, and in a brief overview, a computer system 5 in one embodiment includes a client computer, also referred to as a client, in communication with a server computer 15, also referred to as a server, over a communication channel. 18. Communication channel 18 may include network 20. For example, the communication channel 18 can go over a local area network (LAN) such as a company intranet, or a wide area network (WAN) such as the Internet network, or the WWW network.

In another embodiment, computer system 5 includes multiple clients (eg 10 ') that are in communication with network 20, over additional communication channels (eg 18'). Although illustrated with two clients 10,10 '(generally 10) and communication channels 18, 18' (generally 18), any number of clients 10 and any number of communication channels 18 can be used as part of the computer system 5 .

In one embodiment, the server 15 includes a processor 25, and memory 30 that communicates over a system bus 32. Memory 30 may include random access memory (RAM) and / or read-only memory (ROM). In another embodiment, server 15 accesses memory 30 from a remote point (eg, another computer, or an external storage device).

Client 10 and server 15 establish a first communication session on communication channel 18. In one embodiment, client 10 transmits authentication credentials to server 15, so that server 15 can authenticate the user. The authentication credentials can be any information that the user who requests access to the server 15 considers confidential. Examples of authentication credentials include a login password, credit card information, social security number, phone number, address, biometric information, time-varying access code, and a digital certificate.

After receiving the authentication credentials, the server 15 generates an encryption key. In one embodiment, the encryption key is a random number. The server 15 then encrypts the authentication credentials with the key, so that an attacker who gains access to the server 15 cannot access the authentication credentials without the key. The server 15 also generates a session identifier (SID), to identify the communication session that is established between the client 10 and the server 15. Then the server 15 stores the encrypted authentication credentials, with the SID and memory 30, and transmits the SID and the key to the client 10 over the network 20. Upon receipt by the client of the SID and the key, the server 15 proceeds to destroy (ie, erase) the key in its memory 30.

If the first communication session between client 10 and server 15 ends, for example abnormally, the new session can be re-established without prompting the user to re-enter their authentication credentials. When client 10 and server 15 reestablish a second communication session, client 10 relays the key and SID to server 15. The server 15 uses the SID to locate the encrypted authentication credentials in the memory of the server 30, and uses the key to decrypt the encrypted authentication credentials. The server 15 then authenticates the user, verifying the user's authentication credentials.

For illustrative purposes, following an abnormal termination of a first communication session, in which the user's login password was the authentication credential, client 10 attempts to establish a second communication session with server 15. As part of The request to the server 15 to establish the second communication session, the client 10 transmits the key and the SID of the first communication session terminated, to the server 15. Instead of requiring the user to enter the user's login password again, the server

ES 2 279 871 T3 uses the SID to locate the encrypted login password, associated with the user, and uses the key to obtain the user's login password, from the memory of the server 30.

In more detail, and still referring to Figure 1, the client 10 can be any computing device (for example a personal computer, a decoder, a telephone, a handheld device, a phone booth, etc.) that can communicate with the server 15 and can provide a user interface 33. Client 10 can be connected to communication channel 18, through a variety of connections including standard phone lines, LAN or WAN connections (e.g. T1, T3, 56kb, X.25), broadband connections (ISDN , Frame Relay Network, ATM), and wireless connections. An example of a user interface 33 is a web browser (for example the Microsoft browser^® Internet Explorer, and / or Netscape browser^®).

Similar to client 10, server 15 can be any of the computing devices described above (for example a personal computer) that can access memory 30 and can communicate with client 10. Server 15 can establish communication over the communication channel 18 using a variety of communication protocols (eg IC, HTTP TCP / IP, IPX, SPX, NetBIOS, Ethernet, RS232, and direct asynchronous connections).

Server 15 includes key generator 35, SID generator 38, encryption device 40, key destroyer 45, and decryption device 48. Key generator 35 generates a key when server 15 receives credentials from authentication from client 10. In one embodiment, key generator 35 generates a random number. In another embodiment, the key generator 35 derives the key from a characteristic of the server 15. Concrete examples include the key generator 35 deriving the key from the temperature of the processor 25, the time the server 15 received the authentication credentials, and the number of keys stored in memory 30. In another embodiment, the key and the authentication credentials are the same size (for example, eight bits). In another embodiment, the key generator 35 is a software module. In another embodiment, the key generator 35 is a random number generator.

The SID generator 38 generates the unique SID that enables the user 15 to identify a particular communication session. In one embodiment, the SID generator 38 is a software module. In another embodiment, the SID generator 38 is a random number generator.

The encryption device 40 encrypts the key with the authentication credentials, to create encrypted authentication credentials. In another embodiment, the encryption device 40 encrypts the key with the authentication credentials, by performing an exclusive OR (ie XOR) operation, on the key and the authentication credentials. In another embodiment, the encryption device 40 adds the authentication credentials to the key, to encrypt the authentication credentials; that is, the encryption device 40 performs a "Caesar encryption" on the authentication credentials, using the key as the offset value. It should be clear that the encryption device 40 can carry out any type of manipulation on the authentication credentials, insofar as the server 15 can decrypt the encrypted authentication credentials, with the key.

In one embodiment, the encryption device 40 is a software module that executes mathematical algorithms on the authentication key and credentials to create the encrypted authentication credentials. In another embodiment, the encryption device 40 is a server logic gate 15, such as an exclusive-OR (XOR) gate. In another embodiment, the encryption device 40 performs a digest function such as MP4, MP5, and SHA-1, and on authentication credentials.

In one embodiment, the encryption device 40 stores the encrypted authentication credentials and SID, in a table 55 in memory 30. In another embodiment, the encryption device 40 stores the encrypted authentication credentials in table 55, and the SID generator 38 stores the SID in table 55. In one embodiment, table 55 is in memory area 30 allocated by processor 25 for use by encryption device 40. In another embodiment, the encryption device 40 stores the encrypted authentication credentials in a database (not shown).

In one embodiment, the server 15 uses the SID as a vector for locating the encrypted authentication credentials, in table 55. Thus, the server 15 can locate the encrypted authentication credentials, by using a specific SID (since each encrypted authentication credential created by encryption device 40, is associated with a single SID).

The key destroyer 45 deletes the key, once the server 15 determines that the key is no longer needed. In one embodiment, the key destroyer 45 is a delete function of a software program, such as the operating system of the server 15.

The decryption device 48 decrypts the encrypted authentication credentials, once the server 15 receives the key and SID from the client 10. In one embodiment, the decryption device 48 is a software module that performs the function reverse of the algorithm that the encryption device 40 performs to create the encrypted authentication credentials. In another embodiment, the decryption device 48 is a hardware component (eg, a logic gate), to carry out the reverse operation of the encryption device 40.

ES 2 279 871 T3

In one embodiment, one or more of the key generator 35, the SID generator 38, the encryption device 40, the key destroyer 45, and the decryption device 48, are linked in a software module. In another embodiment, these components 35, 38, 40, 45, 48 can be hardware components, such as logic gates. In a further embodiment, these components 35, 38, 40, 45, 48 are included in a single integrated circuit.

Referring also to FIG. 2A, client 10 establishes a first communication session with server 15, over communication channel 18. Client 10 obtains (step 100) authentication credentials from a user of client 10. In a computer system 5 that does not use an Open System Interconnection (OSI) protocol as the transmission protocol for communication between client 10 and server 15, the authentication credentials can be a login password. , which is required to establish the first communication session. In this embodiment, obtaining the authentication credentials from the user precedes the establishment of the communication session. In another embodiment, the authentication credential is the user's personal information (eg, credit card information, or social security number) that the customer 10 obtains after the first communication session has been established. Then, the client 10 transmits (step 105) the authentication credentials to the server 15, on the communication channel 18.

After the server 15 receives the authentication credentials, the key generator 35 creates (step 110) a first encryption key, for use with the authentication credentials. The encryption device 40 then encrypts (step 115) the authentication credentials, with the first key to generate encrypted authentication credentials. Then the SID generator 38 creates (step 120) a first SID to identify the first communication session. The encryption device 40 then stores (step 125) the encrypted authentication credentials with the first SID, in table 55 described above.

In one embodiment, the encryption device 40 stores the encrypted authentication credentials and the first SID, at a certain location, for more efficient retrieval at a later time. For example, encryption device 40 stores all encrypted authentication credentials and SIDs that have been created, within a predetermined period of time, in RAM 30. Server 15 transfers all encrypted authentication credentials and created SIDs, before a predetermined period, to a second, external memory (not shown). In another embodiment, the encryption device 40 stores the encrypted authentication credentials and the SID in a database.

The encrypted authentication credentials and the SID stored in memory 30 can be arranged in any specific format and / or order. For example, the SID and encrypted authentication credentials can be stored in chronological order, relative to when the encrypted authentication credentials were created.

Then, the server 15 transmits (step 135) the first key and the associated first SID, to the client 10. The client 10 stores (step 140) the first key and the first SID in the client's memory (not shown). Then, the key destroyer 45 clears (step 145) the key stored in memory 30.

In another embodiment, server 15 does not erase the first key from memory 30, until client 10 notifies server 15 that client 10 has received the key. For example, client 10 transmits an acknowledgment message to server 15, after client 10 successfully receives the key. Once the server 15 has the notification (eg the acknowledgment message), the key destroyer 45 then clears (step 145) the key from memory 30. This prevents server 15 from erasing the key before client 10 successfully receives the key. By not deleting the key until receipt of the acknowledgment message, the server 15 can relay the key and SID to the client 10, following a transmission failure.

When deleting the key in step 145, the server 15 does not have the necessary mechanism to decrypt the encrypted authentication credentials, stored in the list 55. Thus, if an attacker accesses the memory 30 of the server 15, the attacker can receive the encrypted authentication credentials, but cannot decrypt encrypted authentication credentials (and therefore cannot read authentication credentials). Briefly, the encrypted authentication credentials stored in the server 15 do not provide information that the attacker can interpret or understand, and the server 15 does not have information to decrypt the encrypted authentication credentials.

Furthermore, the client 10 is the only device that can provide the key for the encrypted authentication credentials. With the possibility of many clients 10 as part of the network 20, an attacker may need to try to gain access to each client (eg 10, 10 ') individually, to find the client 10 that possesses the correct key. This can be tedious and time consuming, and as a result, it can discourage an attacker from attempting to decrypt encrypted authentication credentials.

Furthermore, and also referring to Figure 2B, if the first communication session ends abnormally (step 150), the client 10 can transmit (step 155) the first SID and the first key to the server 15, during a second session communication, without retransmitting authentication credentials.

In another embodiment, the server 15 has a time-out characteristic regarding access to encrypted authentication credentials. For example, the server 15 starts a timer after the first communication has abnormally ended. If the timer reaches a predetermined value before the client 10 resets the

ES 2 279 871 T3 second communication session and transmits the key to the server 15 for decryption, the server 15 deletes the encrypted authentication credentials from the list 55. If no timer is used, the key acts as a password in fact, to future sessions.

Once the server 15 receives the first key and the first SID from the client 10 at the start of, during, the second communication session, the server 15 uses (step 160) the first SID to locate the encrypted authentication credentials, and then the decryption device 48 uses the first key to decrypt the encrypted authentication credentials.

In one embodiment, during the second communication session, the key generator 35 creates (step 170) a second key for the authentication credentials, and the key encryption device 40 thereafter (step 175) encrypts the authentication credentials with the second key, to generate the second encrypted authentication credentials. The SID generator 38 also creates (step 180) a second SID, to identify the second communication session. The encryption device 40 stores the second encrypted authentication credentials with the second SID, in table 55.

The server 15 then transmits (step 185) the second key and the second SID, to the client 10. The client 10 then stores (step 190) the second key and the second SID in memory (not shown) for future retrieval. Then, the key destroyer 45 clears (step 195) the second key from memory 30. Thus, the server 15 can only decrypt the second encrypted authentication credentials, upon receipt of the second key and the second SID from the client 10 . The server 15 has created a new key and a new SID for the second communication session, which are used with the same authentication credentials that the user had transmitted during the first communication session. Therefore, the authentication credentials of a user do not have to be retransmitted on a second communication channel, after an abnormal termination of the first communication session.

Although the invention is discussed in terms of authentication credentials, any confidential information that can be maintained across sessions can be used if there is a communication failure. Thus, if credit card information is required by an application, and credit card information is sent to the server, the subsequent disconnection between the client and the server does not require the credit card information to be re-entered. credit, if this invention is used. Also, although a session identifier or SID, which provides a pointer to stored authentication credentials, is discussed, any number that is suitable as a pointer can be used.

The invention can be carried out in other concrete ways. Therefore, the above embodiments are to be considered, in all respects, illustrative and not limiting of the invention described herein. Thus, the scope of the invention is indicated in the appended claims.