DIGITAL SIGNAL PROCESSING AND COMMUNICATIONS

• Design and Development of Modems
• Cryptography
• Secure Communication
• Error Control Coding
• Compression
• Algorithm Design & Implementation of Standards

A new public key cryptosystem that has computationally less intensive encryption and decryption procedures has been proposed. It can be used in high data bit rate communication systems. Also, a symmetric key cryptosystem that uses non-linear operations and can be realized using linear feedback shift registers is proposed. An algorithm which is a modification of Derome and Chang and Hwang methods to generate RSA keys are proposed. A modification to ElGamal’s public key cryptosystem has been suggested to electronically exchange the keys. Also, several protocols have been developed to distribute the conference key assuming that the participants are placed in different (Ring, Star, and Complete Graph) topologies.

A new transformation called Householder transform in Cm is obtained. This transformation is applied to solve the subspace rotation problem that arises in the Direction of Arrival estimation. Two algorithms are proposed to solve the Linear Programming problem. One of the methods is based on the new definition of the center of the polytope and the other method is derived based on the concept of Angular Projection Matrix.

Video Codec confirming to H.261 standard for video telephony and video conferencing applications is currently being developed. In this project, the encoding and decoding algorithms of binary double error correcting BCH codes were implemented in C as well as in ADSP assembly language by exploiting the intrinsic properties of shift register sequences, Galois field theory in general and the concerned polynomial arithmetic.