Journal of Advanced Computing and Communication Technologies (ISSN: 2347 - 2804) Volume No. 2 Issue No. 1, February 2014 1 Survey on Asymmetric Key Cryptography Algorithms S. Nithya , Dr. E. George Dharma Prakash Raj Computer Science and Engineering, Bharathidasan University, Trichy, India. Computer Science and Engineering ,Bharathidasan University, Trichy, India. niyaa20@yahoo.co.in,georgeprakashraj@yahoo.com ABSTRACT Asymmetric key encryption is also called public key encryption. It uses two keys known as a public and a private key. Data encrypted with one key can be decrypted only with the other key. This paper discusses some public key algorithms and its advantages and disadvantages such as Rivest Shamir Adleman, Diffi-Hellman, Elliptic Curve Cryptography, Elliptic Curve Diffi-Hellman, ElGamal Encryption Algorithm, Knapsack Algorithm, Digital Signature Algorithm and Short Range Natural Numbers. Keywords Cryptography, Rivest Shamir Adleman, Elliptic Curve Cryptography, Diffi - Hellman, Digital Signature. I. INTRODUCTION All public key cryptosystems are based on the notion of a one-way function. Which depending on the public key, converts plaintext into cipher text using are relatively small amount of computing power but whose inverse function is extremely expensive to compute, so that an attacker is not able to derive the original plaintext from the transmitted cipher text within a reasonable time frame. In public key cryptography, each user or the device taking part in the communication have a pair of keys, a public key and a private key, and a set of operations associated with the keys to do the cryptographic operations. Only the particular user/device knows the private key whereas the public key is distributed to all users/devices taking part in the communication. It increased security and convenience: private keys never need to be transmitted or revealed to anyone [1]. This paper work focuses on brief descriptions of various public key cryptography algorithms which are discussed on section II and in section III advantages and disadvantages of these algorithms were made in the form of comparative study. II. PUBLIC KEY CRYPTOGRAPHY ALGORITHMS A. Rivest Adi Adleman (RSA) In 1978, Ron Rivest, Adi Shamir, and Leonard Adleman introduced a cryptographic algorithm, which was essentially to replace the less secure National Bureau of Standards (NBS) algorithm. In RSA, this asymmetry is based on the practical difficulty of factoring the product of two large prime numbers, the factoring problem [2]. In such a cryptosystem, the encryption key is public and differs from the decryption key which is kept secret. The RSA algorithm involves three steps: key generation, encryption and decryption. (i) Key generation: R1. Users of RSA must determine two primes at random: p, q R2. Select either e or d and compute the other Primes p, q must not be easily derived from modulus N=p*q R3. Exponent e, d is inverses, so use inverse algorithm to compute the other. (ii) Encryption: R4. To encrypt a message m the sender R5. Obtains public key of recipient Pu= {e.N} R6. Computes: C=M e mod N, where 0≤M<N (iii) Decryption: R7.To decrypts the cipher text c the owner R8.Uses their private key PR= {d, p, q} R9. Computes: M=M d mod N B. Diffi-Hellman key exchange (D-H) The DH algorithm, introduced by Whitfield Diffie and Martin Hellman in 1976, was the first system to utilize “public-key” or “asymmetric” cryptographic keys. These systems overcome the difficulties of “private-key” or “symmetric” key systems because asymmetric key management is much easier [3]. DH is a mathematical algorithm that allows two computers to generate an identical shared secret on both systems, even though those systems may never have communicated with each