Elgamal encryption

The Elgamal algorithm is an asymmetric key encryption algorithm for public key cryptography which is based on Diffie-Hellman key agreement. It was described by Taher Elgamal in 1984. The Elgamal algorithm is used in the free GNU Privacy Guard software, recent versions of PGP, and other cryptosystems. The Digital Signature Algorithm is a signature scheme is a variant of the ElGamal signature scheme, which should not be confused with the Elgamal algorithm.

Efficiency

Encryption under Elgamal requires two exponentiations; however, these exponentiations are independent of the message and can be computed ahead of time if need be. Decryption only requires one exponentiation (plus one division, which is typically much faster). Unlike in the RSA and Rabin systems, Elgamal decryption cannot be sped up via the Chinese remainder theorem.

Related Topics:
Exponentiation - RSA - Rabin - Chinese remainder theorem

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