Digital Signature Standard

DSA (Digital Signature Algorithm) - is the algorithm of digital signature public key, included in the standard DSS (Digital Signature Standard)operating in the United States. Intended for formation (calculations) and verify digital signatures.

Description of a digital signature algorithm

Let p is a prime numbe, q is a prime divisor of p-1, satisfying the conditions:

Select is an element field , with the order of q. To do this, select a random number and calculate . If =1, then select the number again.

Select a random number a in the interval and calculate the value . The number a is a "secret key", and set - public key.

Algorithm to calculate the digital signature

Calculation algorithm of digital signature for a message M is of the form:

1. choose a random integer r, ;

2. calculate ;

3. calculate according to the algorithm SHA-1;

4. check condition : if it is not met, then select a new value r;

5. calculate ;

6. the signature for the message M is a pair .

Algorithm to verify digital signatures

Algorithm to verify digital signatures consists of the following:

1. calculate , , ;

2. calculate ;

3. check the equality ; if it is true, then the signature is accepted; if it is false, then the signature is rejected.

Bibliography

• Черемушкин А.В. Криптографические протоколы. Основные свойства и уязвимости. - М.: Издательский центр "Академия", 2009. — 272 с.