| This dissertation is motivated by the need for a user-friendly and universally adaptable Secure E-Mail Infrastructure. In this dissertation, we design and implement a Secure E-Mail System (SEMS) that is flexible enough to be adapted to various platforms and also fits into other communication environments in addition to e-mail as well. It overcomes the weaknesses of the existing secure e-mail systems/standards and is better in terms of speed, user-friendliness and adaptability.; In designing SEMS, we adopt new algorithms and software architectures that help us in achieving software interoperability. These new algorithms and architectures allow us to accomplish a given task faster with limited resources. The Aryabhata Remainder Theorem (ART) is used in developing faster public-key crypto-algorithms. A parallel version of ART algorithm is designed for higher performance on systems with multiple processors. The extended Lehmer's algorithm for calculating the inverse of a large number is implemented and analyzed, which is again useful in designing fast public-key based algorithms. We also implemented and analyze a modified version of the Rao-Nol stream cipher algorithm called dynamic-key based SEMS stream cipher algorithm. This algorithm generates one-time pad like secure key sequences and is useful as a secret-key encryption algorithm in any secure application. This algorithm is shown to be not only fast but also secure in contrast to the existing encryption algorithms.; Some of the salient features of SEMS include 128-bit fast encryption, timestamps, message integrity checks and digital signatures. In SEMS, we bring together the Certification Authority (CA), the Key Distribution Center (KDC) and the smart card technology in attaining data confidentiality, authentication, data integrity and nonrepudiation.; The SEMS infrastructure was successfully adopted in other applications like Secure Short Messaging Service and ilisting.com. Ilisting.com is an e-commerce web-based system that provides a model for selling and buying a home. |
