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Privacy enhancement for Internet electronic mail: Part I: Message encipherment and authentication procedures (RFC0989) Disclosure Number: IPCOM000004986D
Original Publication Date: 1987-Feb-01
Included in the Prior Art Database: 2001-Jul-13
Document File: 46 page(s) / 62K

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Network Working Group John Linn (BBNCC) Request for Comments: 989 IAB Privacy Task Force

February 1987

Privacy Enhancement for Internet Electronic Mail: Part I: Message Encipherment and Authentication Procedures


This RFC suggests a proposed protocol for the Internet community and requests discussion and suggestions for improvements. Distribution of this memo is unlimited.


This RFC is the outgrowth of a series of IAB Privacy Task Force meetings and of internal working papers distributed for those meetings. I would like to thank the following Privacy Task Force members and meeting guests for their comments and contributions at the meetings which led to the preparation of this RFC: David Balenson, Matt Bishop, Danny Cohen, Tom Daniel, Charles Fox, Morrie Gasser, Steve Kent (chairman), John Laws, Steve Lipner, Dan Nessett, Mike Padlipsky, Rob Shirey, Miles Smid, Steve Walker, and Steve Wilbur.

1 Executive Summary

This RFC defines message encipherment and authentication procedures, as the initial phase of an effort to provide privacy enhancement services for electronic mail transfer in the Internet. Detailed key management mechanisms to support these procedures will be defined in a subsequent RFC. As a goal of this initial phase, it is intended that the procedures defined here be compatible with a wide range of key management approaches, including both conventional (symmetric) and public-key (asymmetric) approaches for encryption of data encrypting keys. Use of conventional cryptography for message text encryption and/or authentication is anticipated.

Privacy enhancement services (confidentiality, authentication, and message integrity assurance) are offered through the use of end-to- end cryptography between originator and recipient User Agent processes, with no special processing requirements imposed on the Message Transfer System at endpoints or at intermediate relay sites. This approach allows privacy enhancement facilities to be incorporated 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.

Linn, Privacy Task Force [Page 1]

RFC 989 February 1987

2 Terminology

For descriptive purposes, this RFC uses some terms defined in the OSI X.400 Message Handling System Model. This section replicates a portion of X.400's Section 2.2.1, "Description of the MHS Model: Overview" in order to make the terminology clear to readers who may not be familiar with the OSI MHS Model.

In the [MHS] model, a user is a person or a computer application. A user is referred to as either an originator (when sending a message) or a recipient (when receiving one). MH Service elements define the set of message types and the capabilities that enable an originator to transfer messages of those types to one...