Overview of digital signature algorithms supported by OpenSSL

In this section, we will review the digital signature algorithms that are supported by OpenSSL and give some recommendations on which algorithms to use.

Reviewing RSA

The Rivest-Shamir-Adleman (RSA) algorithm was invented by Ronald Rivest, Adi Shamir, and Leonard Adleman. Ronald Rivest is the same person who invented symmetric encryption algorithms from the RC family and message digest algorithms from the MD family. The RSA algorithm was first published in 1977. It was the first popular asymmetric crypto algorithm.

RSA is quite a universal algorithm since it can both encrypt and sign messages. RSA is the slowest algorithm to sign but the fastest to verify for the same security level among the digital signature algorithms provided by OpenSSL.

The speed of both signing and verification depends on the key size. The signing speed quickly drops with the growth of the key size. The verification speed also drops, but...