1. DIGITAL SIGNATURE ALGORITHM

2. The National Institute of Standards and Technology (NIST) has published Federal Information Processing Standard FIPS 186, known as the Digital Signature Standard (DSS). The DSS makes use of the Secure Hash Algorithm (SHA) and presents a new digital signature technique, the Digital Signature Algorithm (DSA).

3. DSS APPROACH

4. DSA A 160-bit prime number q is chosen. (hash o/p length) a prime number p is selected with a length between 512 and 1024 bits such that q divides (p-1) Finally,g is chosen to be of the form h (p-1)/q mod p where h is an integer between 1 and (p -1) with the restriction that g must be greater than 1.

5. DSA

6. COMMENTS ON DSA Comments on DSA was originally a suggestion to use a common modulus, this would make a tempting target, discouraged it is possible to do both ElGamal and RSA encryption using DSA routines, this was probably not intended :-) DSA is patented with royalty free use, but this patent has been contested, situation unclear Gus Simmons has found a subliminal channel in DSA, could be used to leak the private key from a library - make sure you trust your library implementer