Method and apparatus for authentication of client server communication

• US 5,349,642 A
• Filed: 11/03/1992
• Issued: 09/20/1994
• Est. Priority Date: 11/03/1992
• Status: Expired

• Current Assignee: EMC Corporation (Dell Technologies Inc.)
• Original Assignee: Novell Incorporated (Open Text Corporation)
• Inventors: Kingdon, Kevin
• Primary Examiner(s): Cangialosi, Salvatore
• Application Number:
  US07/970,611
• Time in Patent Office: 686 Days
• Field of Search: 380/23, 380/25, 380/28, 380/30
• US Class Current: 713/161
• CPC Class Codes: H04L 63/061 for key exchange, e.g. in peer-to-peer networks cryptographic mechanisms or cryptographic arrangements for key agreement H04L9/0838
• CPC Class Codes: H04L 63/067 using one-time keys cryptographic mechanisms or cryptographic arrangements for generation of one-time passwords H04L9/0863
• CPC Class Codes: H04L 63/083 using passwords cryptographic mechanisms or cryptographic arrangements for entity authentication using a predetermined code H04L9/3226
• CPC Class Codes: H04L 63/12 Applying verification of the received information cryptographic mechanisms or cryptographic arrangements for data integrity or data verification H04L9/32
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 9/0827 involving distinctive intermediate devices or communication paths network architectures or network communication protocols using different networks H04L63/18
• CPC Class Codes: H04L 9/3236 using cryptographic hash functions
• CPC Class Codes: H04L 9/3247 involving digital signatures

Abstract

The present invention provides a method and apparatus for message packet authentication to prevent the forging of message packets. After a message packet is created, a secret session key is preappended to the message, and a message digesting algorithm is executed on the altered message to create a message digest. A portion of the message digest, referred to as the signature, is then appended to the actual message when it is sent over the wire. The receiving station strips the signature from the message, preappends the same secret session key and creates its own message digest. The signature of the digest created by the receiving station is compared to the signature of the digest appended by the sending station. If there is a match, an authentic message is assumed. If there is no match, the message is considered as invalid and discarded. An advantage of the present invention is that the session key is never transmitted over the wire. The receiving station (server) already has the key and uses the key along with the message data to recalculate the message digest upon receiving the packet. The shared secret key (session key) is generated during initiation of the NCP session. In addition, cumulative state information is maintained by both the sending station and the receiving station. This state information is also used to authenticate messages.

Claims

1. A method of authenticating a message transmitted between a sender and a receiver comprising the steps of:

generating a message at said sender;

combining a session key with said message to create a first appended message;

calculating a first digest of said first appended message;

combining a first portion of said first digest with said message to create a transmit message;

transmitting said transmit message to said receiver;

removing said first portion of said first digest from said transmit message to result in said message;

combining said session key with said message to generate a second appended message;

calculating a second digest of said second appended message;

comparing said said portion of said first digest and a second portion of said second digest;

authenticating said message when said first portion of said first digest matches said second portion of said second digest.

3. The method of claim 1 wherein said receiver is a server in a client/server network.

4. The method of claim 1 wherein said step of calculating a first digest of said first appended message is accomplished by executing a digest algorithm on said first appended message.

5. The method of claim 4 wherein said digest algorithm is an MD4 digest algorithm.

6. The method of claim 4 wherein a current state of said sender is used as an initial state when executing said digest algorithm to create said first digest.

7. The method of claim 6 wherein said current state is used as an initial state when executing said digest algorithm to create said second digest.

8. The method of claim 7 wherein said current state is advanced when an authenticated message is received.

9. The method of claim 8 wherein said current state is not advanced when an authenticated message is not received.

10. The method of claim 1 wherein said session key is generated by the steps of:

providing a random number sequence challenge to said sender;

requesting a password from a user of said sender;

generating a first pass digest from said password;

combining said first pass digest and said challenge in a buffer;

generating a buffer digest of said buffer;

defining said session key as a first number of bytes of said buffer digest.

2. The method of claim I wherein said sender is a client in a client/server network.

11. Apparatus for authenticating a message transmitted between a sender and a receiver comprising:

means for generating a message at said sender;

means for combining a session key with said message to create a first appended message;

means for calculating a first digest of said first appended message;

means for combining said a first portion of said first digest with said message to create a transmit message;

means for transmitting said transmit message to said receiver;

means for removing said first portion of said first digest from said transmit message to result in said message;

means for combining said session key with said message to generate a second appended message;

means for calculating a second digest of said second appended message;

means for comparing said said first portion of said first digest and a second portion of said second digest;

means for authenticating said message when said first portion of said first digest matches said second portion of said second digest.

12. The apparatus of claim 11 wherein said sender is a client in a client/server network.

13. The apparatus of claim 11 wherein said receiver is a server in a client/server network.

14. The apparatus of claim 11 wherein said first digest of said first appended message is calculated by executing a digest algorithm on said first appended message.

15. The apparatus of claim 14 wherein said digest algorithm is an MD4 digest algorithm.

16. The apparatus of claim 14 wherein a current state of said sender is used as an initial state when executing said digest algorithm to create said first digest.

17. The apparatus of claim 16 wherein said current state is used as an initial state when executing said digest algorithm to create said second digest.

18. The apparatus of claim 17 wherein said current state is advanced when an authenticated message is received.

19. The apparatus of claim 18 wherein said current state is not advanced when an authenticated message is not received.

20. The apparatus of claim 11 further including means for generating a session key comprising:

means for providing a random number sequence challenge to said sender;

means for requesting a password from a user of said sender;

means for generating a first pass digest from said password;

means for combining said first pass digest and said challenge in a buffer;

means for generating a buffer digest of said buffer;

means for defining said session key as a first number of bytes of said buffer digest.