Evolution of unified framework for run time optimization and security enhancement in cryptographic algorithms

Abstract

With the rapid usage of data communication, security is becoming a more crucial issue. The fundamental requirements for security include authentication, confidentiality, integrity, and non-repudiation. To provide such security services, most system uses two major classes of cryptographic algorithms namely symmetric-key and public-key algorithms. In symmetric-key algorithms, same key is used for both encryption and decryption. They usually operate at relatively high speed and are suitable for bulk encryption of messages. Public-key algorithms are based on the idea of separating the key used to encrypt a message from the one used to decrypt it. They are relatively slow and therefore unsuitable for encryption of large bulky messages. Most of the number-theory based cryptographic algorithms used for message transmission are deterministic. They always encrypt the plaintext into the same ciphertext. If an eavesdropper knows the plaintext message belongs to a small set, the original message can easily be recovered. However, it is sometimes easy to compute partial information about the plaintext from the ciphertext. For example, in RSA, if c = me mod n is the ciphertext corresponding to a plaintext m, then (c/n) = (me/n) = (m/n)e = (m/n). Since e is odd, an adversary can easily gain one bit of information about m, based on the Jacobi symbol (m/n). It is easy to detect when the same message is sent twice and hence it is not fully secured. For these reasons, probabilistic encryption is introduced. Though the probability encryption produces different ciphertext for the same plaintext, its behavior is partly controlled by random events. The security of these algorithms purely depend on the level of randomness i.e., more randomness means more security. Moreover, to encrypt a character using either deterministic or probability encryption algorithms, numerals corresponding to the plaintext (preferably ASCII) are always considered.