Abstract:

Extended research and practical application about DSA(Digital Signature Algorithm) are very wide, they are all based on the security of DSA itself. Aiming at the main known attacks of evaluating secret key with the help of public data, exhaustive groping attack, birthday attack and fabrication attack based on known message, security of DSA is analyzed. The computing expressions are given about the attack methods. It is indicated that these attacks are equal to or more difficult than solving the discrete logarithm problem. Upon that, security intensity of DSA is shown a certain content. The potential weakness of DSA is given, lying in random number k, message independent signature r, sharing modulus p  and  q, Hash function, etc. And the corresponding solutions are presented.A favorable random numbers generator is designed for selecting right random numbers, so the attacks on low exponential and same random number could be avoided. Length of modulus  p  is selected reasonably, so the attack on the common signature r   could been counteracted. DSA prime is used as modulus in the case of high security intensity and low speed, so the common modulus attack could be resisted. SHA(Secure Hash Algorithm) with enough length message digest is utilized, so security of inline hash function could be ensured.

Key words: digital signature, digital signature algorithm(DSA), security, attack