Digital signature algorithm (DSA) is a variant of the signature algorithm of Schnorr and ElGamal, and is regarded as DSS(DigitalSignature Standard) by NIST in the United States. The following parameters are applied in the algorithm:

Prime number with l bit length. L is a multiple of 64, ranging from 5 12 to1024;

Q: the prime factor of1of p-160;

G: g = h ((p- 1)/q) mod p, h satisfies H.

x:x & lt； Q and x are private keys;

Y: y = g x mod p, (p, q, g, y) is the public key;

H (x): one-way hash function. SHA (secure hash algorithm) is selected in DSS.

P, Q, G can be enjoyed by a group of users, but in practical application, using the male model may bring some threats. The signing and verification protocols are as follows:

1.p generates random numbers k, k.

2.p calculate r = (g k mod p) mod q.

s = ( k^(- 1) (H(m) + xr)) mod q

The signature result is (m, r, s).

3. Calculate w = s (- 1) mod q during verification.

u 1 = ( H( m ) * w ) mod q

u2 = ( r * w ) mod q

V = ((g u1* y U2) module p) module q

If v = r, the signature is considered valid.

DSA is a discrete logarithm problem based on integer finite field, and its security is similar to RSA. An important feature of DSA is that two prime numbers are public, so that when using other people's P and Q, you can confirm whether they are randomly generated or tampered with even if you don't know the private key. RSA algorithm doesn't work.