Method for negotiating weakened keys in encryption systems

• US 20040184606A1
• Filed: 01/21/2004
• Published: 09/23/2004
• Est. Priority Date: 12/18/1998
• Status: Active Grant

• Current Assignee: Gregory G. Rose
• Original Assignee: Gregory G. Rose
• Inventors: Rose, Gregory G.
• Granted Patent: US 7,366,895 B2
• Time in Patent Office: Days
• US Class Current: 380/44
• CPC Class Codes: H04L 2209/80 Wireless network architectures or network communication protocols for wireless network security H04W12/00
• CPC Class Codes: H04L 2463/061 applying further key derivation, e.g. deriving traffic keys from a pair-wise master key cryptographic mechanisms or cryptographic arrangements for generation of secret information including derivation or calculation of cryptographic keys or passwords H04L9/0861
• 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 9/0838 Key agreement, i.e. key establishment technique in which a shared key is derived by parties as a function of information contributed by, or associated with, each of these network architectures or network communication protocols for key exchange in a packet data network H04L63/061
• CPC Class Codes: H04L 9/0861 Generation of secret information including derivation or calculation of cryptographic keys or passwords
• CPC Class Codes: H04L 9/088 Usage controlling of secret information, e.g. techniques for restricting cryptographic keys to pre-authorized uses, different access levels, validity of crypto-period, different key- or password length, or different strong and weak cryptographic algorithms network architectures or network communication protocols for using time-dependent keys in a packet data network H04L63/068
• CPC Class Codes: H04W 12/03 Protecting confidentiality, e.g. by encryption
• CPC Class Codes: H04W 12/041 Key generation or derivation
• CPC Class Codes: H04W 92/18 between terminal devices

Abstract

A method for permitting encrypted communications between two stations which are operable with encryption algorithms that accept encryption keys having work factors with different values, by: in a first determining step, determining the lower one of the different values; providing an initial encryption key having a first work factor value; comparing the first work factor value with the lower one of the work factors determined in the determining step; when, in the comparing step, the first work factor value is greater than the lower one of the work factor values determined in the determining step, performing the following steps: performing a first hash function on the initial encryption key to produce a first output, and deriving from the first output a first intermediate key having a work factor value not greater than the lower one of the different work factor values determined in the determining step; performing the first hash function on the first intermediate key to produce a second output, and deriving from the second output a final encryption key having a work factor value not greater than the lower one of the different work factor values determined in the determining step; and using the final encryption key to encrypt communications between the two stations; and when, in the comparing step, the first work factor value is found to not be greater than the lower one of the work factor values determined in the determining step, using the initial encryption key to encrypt communications between the two stations.

Claims

1. A method for permitting encrypted communications between two stations which are operable with compatible encryption algorithms that accept encryption keys having work factors with respectively different values, comprising:

in a first determining step, determining the lower one of the different work factor values;

providing an initial encryption key having a first work factor value;

comparing the first work factor value with the lower one of the work factor values determined in said determining step;

when, in said comparing step, the first work factor value is found to be greater than the lower one of the work factor values determined in said determining step, performing the following steps;

performing a hash function on a first word that includes the initial encryption key to produce an intermediate key, and deriving from the intermediate key a modified intermediate key having a work factor value not greater than the lower one of the different work factor values determined in said determining step;

performing a hash function on a second word that includes the modified intermediate key to produce a second output, and deriving from the second output a final encryption key having a work factor value not greater than the lower one of the different work factor values determined in said determining step; and

using the final encryption key to encrypt communications between the two stations.

2. Apparatus for permitting encrypted communications between two stations which are operable with compatible encryption algorithms that accept encryption keys having work factors with respectively different values, comprising:

means for determining the lower one of the different work factor values;

means for providing an initial encryption key having a given work factor value;

means for comparing the first work factor value with the lower one of the work factor values;

means for performing a hash function on a first word that includes the initial encryption key to produce an intermediate key, and deriving from the intermediate key a modified intermediate key having a work factor value not greater than the lower one of the different work factor values;

means for performing a hash function on a second word that includes the modified intermediate key to produce a second output, and deriving from the second output a final encryption key having a work factor value not greater than the lower one of the different work factor values; and

means for using the final encryption key to encrypt communications between the two stations if the first work factor value is found to be greater than the lower one of the work factor values.

3. A method for permitting encrypted communications between two stations which are operable with compatible encryption algorithms that accept encryption keys having work factors with respectively different values, comprising:

determining a lowest one of the different work factor values;

providing an initial encryption key with a given work factor value;

comparing the given work factor value with the lowest one of the different work factor values; and

wherein, if the given work factor value is greater than the lowest one of the different work factor values, the method further comprises;

deriving from the initial encryption key a final encryption key having a work factor value not greater than the lowest one of the different work factor values; and

using the final encryption key for the encrypted communications.

4. The method of claim 3, further comprising:

performing a first hash function on a first word that includes the initial encryption key to produce an intermediate key having a given length determined by the first hash function, and deriving the final encryption key from the intermediate key.

5. The method of claim 4, wherein the first word comprises a combination of the initial encryption key and a salt.

6. The method of claim 4, wherein if the given work factor is greater than the lowest one of the different work factor values, the method further comprises:

deriving from the intermediate key a modified intermediate key having a work factor value not greater than the lowest one of the different work factor values; and

deriving from the final encryption key from the modified intermediate key.

7. The method of claim 6, further comprising:

performing a second hash function on a second word that includes the modified intermediate key to produce a second output; and

deriving from the second output the final encryption key.

8. The method of claim 7, wherein the second word is combination of the intermediate key and a salt.

9. The method of claim 7, wherein the second hash function is different from the first hash function.

10. The method of claim 6, wherein deriving the modified intermediate key comprises:

setting a selected number of the most significant bit values of the intermediate key to zero.

11. The method of claim 10, wherein the selected number is equal to a number resulting from subtracting the lowest one of the different work factor values from the given length of the intermediate key.

12. The method of claim 3, wherein if the given work factor value is not greater than the lowest one of the different work factor values, the method further comprises:

using the initial encryption key for the encrypted communications.

13. A method for permitting encrypted communications between two stations which are operable with compatible encryption algorithms having an accepted key length, wherein the encryption algorithms accept encryption keys having work factors with respectively different values, comprising:

generating an initial encryption key;

determining a lowest one of the different work factor values;

comparing the accepted key length and the lowest one of the different work factor values; and

wherein, if the lowest one of the different work factor values is less than the accepted key length, the method further comprises;

deriving from the initial encryption key a final encryption key having a work factor value not greater than the lowest one of the different work factor values; and

using the final encryption key for the encrypted communications.

14. The method of claim 13, further comprising:

performing a first hash function on a first word that includes the initial encryption key to produce an intermediate key having a given length determined by the first hash function, and deriving the final encryption key from the intermediate key.

15. The method of claim 14, wherein the first word comprises a combination of the initial encryption key and a salt.

16. The method of claim 14, wherein if the lowest one of the different work factor values is less than the accepted key length, the method further comprises:

deriving from the intermediate key a modified intermediate key having a work factor value not greater than the lowest one of the different work factor values; and

deriving from the final encryption key from the modified intermediate key.

17. The method of claim 16, further comprising:

performing a second hash function on a second word that includes the modified intermediate key to produce a second output; and

deriving from the second output the final encryption key.

18. The method of claim 17, wherein the second word is combination of the intermediate key and a salt.

19. The method of claim 17, wherein the second hash function is different from the first hash function.

20. The method of claim 16, wherein deriving the modified intermediate key comprises:

setting a selected number of the most significant bit values of the intermediate key to zero.

21. The method of claim 20, wherein the selected number is equal to a number resulting from subtracting the lowest one of the different work factor values from the given length of the intermediate key.

22. The method of claim 13, wherein if the lowest one of the different work factor values is greater than the accepted key length, the method further comprises:

using the initial encryption key for the encrypted communications.

23. The method of claim 22, wherein using the initial encryption key comprises:

using a selected number of the least significant bits of the initial encryption key, wherein the selected number is equal to the accepted key length.