Symmetric and Asymmetric Schemes with Ideal Secrecy and Secure Transaction over Physical Channel

This thesis is to formulate and address the requirement of confidentiality of bulk data communication along with the exchange of keys and authentication of communicating parties. Apart from developing cryptographic schemes for secure communication of data an objective in this thesis is also to assure the security of these schemes from cryptanalytic point of view. The class of schemes that are addressed in this thesis fall into the following categories. First, the bulk transmission of data using a symmetric key scheme. Second, the public key scheme for authentication and key exchange. Third, a scheme which addresses bulk encryption and decryption with security for communication over the physical layer. Fourth is about the construction of feedback shift registers with long periods.