1. Integrating Diffie-Hellman Key Exchange into the Digital Signature Algorithm IEEE Communications Letters, March 2004 Lein Harn, Manish Metha and Wen- Jung Hsin Presented by Jung-Chen Liu Date ： 2004/04/13

2. Outline Motivation Introduction Secure DH+DSA key exchange protocols Security analysis Contributions

3. Motivation NIST has published a series of security standards under Federal Information Proceeding Standard (FIPS). But for far, there is no FIPS standard for key agreement between two parties. DH key agreement(1976) did not provide authentication.

4. Introduction In 1993, Arazi suggested replacing the message in the DSA algorithm with DH exchange key (authentication). In 1994, Nyberg pointed out it cannot resist the known key attack.

5. Secure DH+DSA key exchange protocols A. One-Round Protocol A. One-Round Protocol ： supports noninteractive applications, such as secure e-mail transmission. B. Two-Round Protocol B. Two-Round Protocol ： interactive application, K AB and K BA are the shared secret keys. C. Three-Round Protocol C. Three-Round Protocol ： key confirmation.

6. One-Round Protocol User A User B Verify DSA signature (r A, s A ) of message m A (m A, s A )

7. Two-Round Protocol User A User B (m A, s A ) (m B, s B )

8. Three-Round Protocol User A User B mAmA (m B, s B ) sAsA

9. Security analysis

10. Contribution This protocol provide multiple secret keys, one for each direction. This arrangement conforms most standard protocols, ex. SSL IPSec… The shared secret key is included in the signature. Prevent the known key attack and key replay attack. Three-round protocol achieves key confirmation. Prevent unknown key attack.