Stream cipher based on quasigroup string transformations in Zp∗Z_p^*

In this paper we design a stream cipher that uses the algebraic structure of the multiplicative group \bbbz_p^* (where p is a big prime number used in ElGamal algorithm), by defining a quasigroup of order $p-1$ and by doing quasigroup string transformations. The cryptographical strength of the proposed stream cipher is based on the fact that breaking it would be at least as hard as solving systems of multivariate polynomial equations modulo big prime number $p$ which is NP-hard problem and there are no known fast randomized or deterministic algorithms for solving it. Unlikely the speed of known ciphers that work in \bbbz_p^* for big prime numbers $p$, the speed of this stream cipher both in encryption and decryption phase is comparable with the fastest symmetric-key stream ciphers.Comment: Small revisions and added reference

Quasi group based crypto-system

For electronic commerce and other applications it is required to encrypt data that is transmitted over an unsecured channel. The data is encrypted/randomized using a key. Algorithms such as DES and ECC randomize the data such that un-authorized user cannot decrypt it .This thesis presents a practical implementation of a quasi group based multilevel, indexed scrambling transformation for use in signal encryption. Results of experiments with text and speech scrambling are presented. It is shown that the quasi group transformation maximizes the entropy at the output, which is desirable for a good system. This system provides extremely large group of keys that ensures enhanced security. It can work in either the chain mode or the block mode. Block mode is more tolerant to errors compared to the chain mode

A Message Authentication Code based on Latin Squares

. This is a proposal on the construction of a Message Authentication Code (MAC) based on Latin Squares. The design is inspired by Wegman-Carter construction which takes advantage of provable security. The MAC is described and its security is examined. It is also compared with other MACs and its advantages are shown. 1 Introduction Message Authentication Code (MAC) is one of the most common cryptographic tools for providing authentication in a wide range of applications. A MAC takes a secret key to generate a checksum for a given message or to verify an existing (previously generated) checksum. In most designs, a MAC is constructed from an existing hash function. A checksum is a fixed length string that follows a message to provide its integrity. We refer to the process of generating a checksum of a given message as signing and the process of verifying an existing checksum as verifying. A MAC uses a symmetric key that will be used in both signing and verifying processes, and therefore..