Re: [Dcrup] Working Group Last Call for draft-ietf-dcrup-dkim-crypto

["John Levine" <[e-mail]>]

>Simultaneously: John, your comments in reply to this?

>> 1.  The existing RFC 6376 signature algorithms specify what to use for
>> hash-
>> alg.  That's missing from the Ed25519-SHA256 definition in section 3.  As
>> implied by the name (and discussed on the list), the hash-alg should be
>> SHA256.  Recommend replacing the leading sentence phrase in section 3 with:
>>
>> The Ed25519-SHA256 Signing Algorithm computes a message hash as described
>> in
>> Section 3.7  of [RFC6376] using SHA-256 [FIPS-180-3-2008] as the hash-alg,

That's fine.

>> 2.  For clarity, per some of the IETF LC feedback on draft-ietf-dcrup-dkim-
>> usage, recommend adding after the main body of section 3 and before the
>> note:
>>
>> This is an additional DKIM signature algorithm added to Section 3.3 of
>> [RFC6376] as envisioned in Section 3.3.4 of [RFC6376].

Also fine.

>> 3.  Private key storage format
>>
>> Unlike RSA, Ed25519 does not appear to have a standardized textual
>> format.  I
>> think it might make sense to specify that for DKIM Ed25519 purposes the
>> private key is stored as the base64 encoded output of the RFC 8032 Section
>> 5.1.5 private key generation processes.  This would provide a (slightly)
>> human readable private key representation that could be used by different
>> implementations so that operators can safely switch implementations without
>> regenerating keys and that are more understandable for trouble shooting
>> purposes.

OK by me but I'm no crypto expert.  Perhaps we could ask the openssl folks what
key format they'll be using.

>> 4.  Examples
>>
>> It would be nice to have at least one signing example for implementers to
>> use to verify correctness.  I currently have either a signing bug or a
>> verification bug in my work and I'm not sure which.  If I had a known
>> correct example to bounce my signing results against, that would help a lot.

A reasonable albeit somewhat painful request.  What ed25519 library are you using?

R's,
John
-- 
Regards,
John Levine, [e-mail], Primary Perpetrator of "The Internet for Dummies",
Please consider the environment before reading this e-mail. https://jl.ly