ElGamal encryption

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In cryptography, the ElGamal encryption system is a public-key encryption algorithm based on the Diffie–Hellman key exchange. It was described by Taher Elgamal in 1985. ElGamal encryption is used in the free GNU Privacy Guard software, recent versions of PGP, and other cryptosystems. The Digital Signature Algorithm (DSA) is a variant of the ElGamal signature scheme, which should not be confused with ElGamal encryption. ElGamal encryption can be defined over any cyclic group G {\displaystyle G} , like multiplicative group of integers modulo n if and only if n is 1, 2, 4, pk or 2pk, where p is an odd prime and k > 0. Its security depends upon the difficulty of the Decisional Diffie Hellman Problem in G {\displaystyle G} .

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