Secure Electronic Post Office

This paper describes the Secure Electronic Post Office (SEPO), a new electronic mail (e-mail) system that provides authentication, authorization, secure communications, pipeline, multiple receiver, anti-reply attack, assurance of message reception and routing control. SEPO is easy to implement, cross-platform, to build a regional or global e-mail system. For the internationalization purpose, the e-mail address SEPO adopts is a unicode character. The typical SEPO e-mail is composed of a postmark, stamp, envelope and letter. The letter is a simple file format to combine contexts, e-mail header, attachment files, etc. Unlike MIME, it does not increase the data size up to 33% and it is easy to process and requires less error handling. The envelope is designed to pack the letter and add some attributes about the sender, receiver and encryption of the letter. Furthermore, each e-mail address of SEPO can own several public key pairs to authenticate the e-mail and encrypt the symmetric session key used for encrypting the letter before transfer. The symmetric session key is stored in the envelope after it has been encrypted by the receiver public key.