Implementation Of Secure Email System Supporting Base91 Encoding

Electronic mail (Email) is one of the most important services in Internet. With the rapid development of Internet, Email has become a popular communication tool. Nowadays, the users of Email come from not only the scientific and educational professions but also ordinary family. Information transmitted by Email expands from common textual information to multimedia information including audio and video. With the further application of Email, the users pay more and more attention to such indexes as the security, stability and transmission speed of the Email system.This paper analyzes the menace that Email system faces and proposes effective solutions to enhance its security. What's more, the paper does a detailed discussion on how to implement the S/MIME protocol based on PKI and SASL authentication mechanism in secure Email system. Meanwhile the paper analyzes the deficiency of current transmission coding and describes a new digital transformation method, base91 encoding, with high encoding efficiency but low data extension. This method can obviously improve the transmission speed when used in electronic mail system.After the investigation of the related protocols of Email, the author developed a kind of secure Email agent software based on the international standards, which can support base91 encoding. Besides having the traditional function of receiving and sending Email, the software puts great emphasis upon providing the secure services of confidentiality, authentication, integrity, non-repudiation and so on.