Public key algorithms |
| In a public-key cryptography system (unlike secret-key systems), the sender and the receiver of that message hasn't to know the same secret-key. In fact they use 2 pair of key each one: a public-key and a private-key. There are several public-key systems: RSA is a cryptosystem for both encryption and authentication developed in 1977 by Ron Rivest, Adi Shamir and Leonard Adleman. This algorithm is based on the factoring problem. RSA is usually combined with a secret-key algorithm such as DES for example. In fact DES is much faster than RSA. RSA provide key size up to 2048 bit (see RSA-129). ELGAMAL is an encryption algorithm based on the discrete logarithm problem. Analysis shows that ELGAMAL and RSA have similar security for equivalent key length. However ELGAMAL algorithm is slower than RSA. Elliptic curves cryptosystem is an algorithm similar to RSA and ELGAMAL, but it is based on elliptic curves addition operation. The Merkle-Hellman KNAPSACK cryptosystem was developed in 1978. It is based on the subset sum problem in combinatorics. LUC is a cryptosystem developed by a group of researchers in Australia and New Zealand. It is based on Lucas sequences. McEliece is a cryptosystem based on algebraic coding theory. Probabilistic encryption is a different approach for encryption discovered by Goldwasser and Micali. Unlike conventional cryptosystems, here a message is encrypted into one of many possible ciphertexts. |
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