Examples of Asymmetric Encryption Algorithms

Examples of Asymmetric Encryption Algorithms

Rivest-Shamir-Adleman (RSA) Algorithm

RSA is an asymmetric key cryptosystem that offers both encryption and digital signatures that provides non-repudiation, integrity, and authentication of source Ron Rivest, Adi Shamir, and Leonard Adleman developed RSA in 1977, and as you might have surmised, RSA stands for the first letter of its inventors' surnames.

The RSA public (asymmetric) key algorithm is one of the most popular and secure (given long key lengths) encryption methods available in the asymmetric cryptography area. The algorithm capitalizes on the fact that there is no efficient way to factor very large prime numbers. Therefore, the security of RSA is based on the assumption that factoring is difficult. Factoring is defined as taking a number and finding the numbers that can be multiplied together to calculate that number. As the speed of processors have become faster, RSA allows for the increase of key sizes that counter the possibility of factoring and therefore deducing the private key.

Diffie-Hellman-Merkle is a key negotiation algorithm and does not provide for message confidentiality. It is used to enable two entities to exchange or negotiate a secret symmetric key that will be used subsequently for message encryption using symmetric key cryptography.

The Diffie-Hellman-Merkle algorithm can be extremely useful for applications such as PKI and others where the generation of symmetric session keys are required. It is often referred to as a session key negotiation algorithm. Diffie-HellmanMerkle is based on a discrete logarithm hard math problem.

Diffie-Hellman-Merkle can be summarized as follows: It is a key agreement protocol whereby two parties, without any prior arrangements, can agree upon a secret symmetric key that is known only to them. This secret key can then be used, for example, to encrypt further communications between the parties from that point on using symmetric key cryptography.

The Diffie-Hellman-Merkle key agreement requires that both the sender and recipient of a message have their private and public key pairs. By combining one's private key and the other party's public key, both parties can compute the same shared secret number that ends up being the symmetric session key. A "session key" is a symmetric key that is used only for that particular session.

ElGamal

The ElGamal cryptographic algorithm is based on the work of Diffie-HellmanMerkle, but it also includes the ability to provide message confidentiality and digital signature service, not just session key negotiation.

Although not technically correct, some people refer to ElGamal as a combination of the Diffie-Hellman-Merkle and RSA algorithms. The ElGamal algorithm is based on the same mathematical functions of discrete logs.