I am the assigned Gen-ART reviewer for this draft. The General Area Review Team (Gen-ART) reviews all IETF documents being processed by the IESG for the IETF Chair. Please treat these comments just like any other last call comments. For more information, please see the FAQ at . Document: draft-ietf-dcrup-dkim-usage-?? Reviewer: Jari Arkko Review Date: 2017-09-13 IETF LC End Date: 2017-09-13 IESG Telechat date: Not scheduled for a telechat Summary: This document defines modern day requirements for the cryptographic algorithms used for DKIM. The document is well written, short, and sets requirements that are quite appropriate. I have no comments beyond one small issue/question related to the wording of the main requirement. Major issues: Minor issues: The document says: Signers MUST sign using rsa-sha256. Verifiers MUST verify using rsa-sha256. rsa-sha1 MUST NOT be used for signing or verifying. I was slightly surprised by the wording of the middle requirement about MUST verify using rsa-sha256. Given that new algorithms may be defined in the future (and indeed, draft-ietf-dcrup-dkim-crypto already defines some), wouldn't a "MUST implement" type wording be more suitable? Particularly when the third requirement prohibits the use of weak algorithm. With the middle requirement, how could any other, future stronger algorithm be used? Or is the idea that the definition of those algorithms would update these requirements? Or am I missing something? Nits/editorial comments: