Cryptography Reference
In-Depth Information
Fig. 10.2
Principle of EMSA-PSS encoding
10.3 The Elgamal Digital Signature Scheme
The Elgamal signature scheme, which was published in 1985, is based on the diffi-
culty of computing discrete logarithms (cf. Chap. 8). Unlike RSA, where encryption
and digital signature are almost identical operations, the Elgamal digital signature
is quite different from the encryption scheme with the same name.
10.3.1 Schoolbook Elgamal Digital Signature
Key Generation
As with every public-key scheme, there is a set-up phase during which the keys are
computed. We start by finding a large prime
p
and constructing a discrete logarithm
problem as follows:
