Privacy Enhanced Mail (PEM) was the first serious effort to secure Internet mail. The Internet Resources Task Force (IRTF) Privacy and Security Research Group (PSRG) did the initial design. The Internet Engineering Task Force (IETF) PEM Working Group continued development for three years, resulting in a four- part Proposed Internet Standard published in early 1993 [64] [56] [5] [55]. PEM is a broad standard suite, it provides encryption, authentication, message integrity and key management. PEM supports both symmetric and asymmetric (public- key) key management schemes. PEM uses DES for encryption, MD2 or MD5 for authentication and with RSA for public-key management. The standard also allows for different suites.
