1. Executive Summary

This document defines message encryption and authentication procedures, in order to provide privacy-enhanced mail (PEM) services for electronic mail transfer in the Internet. It is intended to become one member of a related set of four RFCs. The procedures defined in the current document are intended to be compatible with a wide range of key management approaches, including both symmetric (secret-key) and asymmetric (public-key) approaches for encryption of data encrypting keys. Use of symmetric cryptography for message text encryption and/or integrity check computation is anticipated. RFC 1422 specifies supporting key management mechanisms based on the use of public-key certificates. RFC 1423 specifies algorithms, modes, and associated identifiers relevant to the current RFC and to RFC 1422. RFC 1424 provides details of paper and electronic formats and procedures for the key management infrastructure being established in support of these services.

Privacy enhancement services (confidentiality, authentication, message integrity assurance, and non-repudiation of origin) are offered through the use of end-to-end cryptography between originator and recipient processes at or above the User Agent level. No special processing requirements are imposed on the Message Transfer System at endpoints or at intermediate relay sites. This approach allows privacy enhancement facilities to be incorporated selectively on a site-by-site or user-by-user basis without impact on other Internet entities. Interoperability among heterogeneous components and mail transport facilities is supported.

The current specification's scope is confined to PEM processing procedures for the RFC-822 textual mail environment, and defines the Content-Domain indicator value "RFC822" to signify this usage. Follow-on work in integration of PEM capabilities with other messaging environments (e.g., MIME) is anticipated and will be addressed in separate and/or successor documents, at which point additional Content-Domain indicator values will be defined.