]> Mailpile ehf

Baronsstigur Iceland bre@mailpile.is

Independent

juga@riseup.net

American Civil Liberties Union

125 Broad St. New York, NY 10004 USA dkg@fifthhorseman.net

int openpgp Internet-Draft This is a tombstone document of an abandoned effort to provide end-to-end cryptographic protections for e-mail headers. It has been superseded by RFC 9788.

This Document Is Deprecated This document has been superseded by .

References Normative References S/MIME version 3.1 introduced a mechanism to provide end-to-end cryptographic protection of email message headers. However, few implementations generate messages using this mechanism, and several legacy implementations have revealed rendering or security issues when handling such a message. This document updates the S/MIME specification (RFC 8551) to offer a different mechanism that provides the same cryptographic protections but with fewer downsides when handled by legacy clients. Furthermore, it offers more explicit usability, privacy, and security guidance for clients when generating or handling email messages with cryptographic protection of message headers. The Header Protection scheme defined here is also applicable to messages with PGP/MIME (Pretty Good Privacy with MIME) cryptographic protections. Informative References xkcd

Document History Significant changes between version -03 and -04:

• Update "Tombstone" to point to released RFC9788.

Significant changes between version -02 and -03:

• "Tombstone" this document in favor of draft-ietf-lamps-header-protection

Significant changes between version -01 and -02:

• Added S/MIME test vectors in addition to PGP/MIME
• Legacy Display parts should now be text/plain and not text/rfc822-headers
• Cryptographic Payload must have protected-headers parameter set to v1
• Test vector sample Message-Ids have been normalized
• Added encrypted-only (unsigned) test vectors, at the suggestion of Russ Housley

Changes between version -00 and -01:

• Credit Randall for "correct horse battery staple".
• Adjust test vectors to ensure no line in the generated .txt format exceeds 72 chars.
• Minor formatting cleanup to appease idnits.
• Update references to more recent documents (RFC 2822 -> 5322, -00 to -01 of draft-ietf-lamps-header-protection-requirements).

Acknowledgements The set of constructs and algorithms in this document has a previous working title of "Memory Hole", but that title is no longer used as different implementations gained experience in working with it. These ideas were tested and fine-tuned in part by the loose collaboration of MUA developers known as . Additional feedback and useful guidance was contributed by attendees of the OpenPGP e-mail summit (). The following people have contributed implementation experience, documentation, critique, and other feedback:

• Holger Krekel
• Patrick Brunschwig
• Vincent Breitmoser
• Edwin Taylor
• Alexey Melnikov
• Russ Housley

The password example used in previous versions comes from .