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Re: Signature Crypto Algorithm Details

From: Tim Bray <tbray@textuality.com>
Date: Fri, 14 Jan 2022 10:21:38 -0800
Message-ID: <CAHBU6ivaDkhmYyJKRgW=t+ARZ6pk5Hkea8PbqZ6YvH75iHDkzg@mail.gmail.com>
To: Henry Story <henry.story@gmail.com>
Cc: Justin Richer <jricher@mit.edu>, HTTP Working Group <ietf-http-wg@w3.org>
On Fri, Jan 14, 2022 at 10:01 AM Henry Story <henry.story@gmail.com> wrote:


> ( I also prefer my key data to be in plain text rather than Base64 encoded
> binary ASN.1
> which just makes crypto feel like dark magic.)
>
> I got ed25519 to work in Java easily, but I think it is missing in the
> WebCrypto API in
> the browser. At least that is what my initial research suggested.
>

FWIW, here are my explorations of how to interchange ed25519 keys in Java &
Go: https://www.tbray.org/ongoing/When/202x/2021/04/19/PKI-Detective


>
> https://github.com/httpwg/http-extensions/issues/1509#issuecomment-1009913760
>
> It would make a big difference if it were available in the browsers by
> default I think.
> Perhaps someone can relay that to the right folks?
>
> Henry
>
>
> > On Fri, Jan 14, 2022 at 8:42 AM Justin Richer <jricher@mit.edu> wrote:
> >> Hi all,
> >>
> >> In the Signatures draft, we’ve got a bunch of strictly-defined
> algorithms for people to be able to use out of the box. Crypto primitives
> are often parameterized, giving a lot of flexibility and choice. The idea
> here though is that if you’re pulling something out of the named algorithm
> registry, you wouldn’t have choices to make about how to apply it. (You
> can, as always, go off and do your own algorithm within your own ecosystem
> without using the registry values.)
> >>
> >> In any event, two elliptic curve algorithms have caught my attention
> the last couple weeks and I am looking to drum up feedback. First, Edwards
> curve algorithms, specifically ed25519. It’s been requested by a number of
> people out there that we add this, so I’ve been working out what parameters
> we’d need within the spec text to make it interoperable. From early
> implementations and feedback, we’ve settled on a PureEdDSA algorithm with
> no pre-hash of the message input, since that seems to be the most common
> and accepted version of this. We’re preparing text to add this to the
> draft, and I’m looking to confirm that choice if anyone has any strong
> feelings on the matter.
> >>
> >> Second, the ECDSA algorithm that we define over curve P256 has its own
> snag that we didn’t realize: the signature in the mathematical model is two
> separate numbers, r and s. We need to encode a single value, and all the
> libraries that I used take the approach that you just concatenate the two
> into a single 64-byte array and call that the signature. However some
> implementors have gotten back to me that their libraries use an alternative
> method of encoding, using ASN.1 to wrap the two integers into an ASN.1
> structure. A quick survey shows that this is supported on many libraries,
> but it does have the drawback of pulling in explicit ASN.1 into the
> signature definition where it isn’t needed elsewhere. I’m currently leaning
> towards more carefully defining the concatenation approach, similar to what
> JOSE uses in this case, but I am seeking feedback on this choice.
> >>
> >> I know that this is a question more for the security/crypto crowd, and
> we’ll be reaching out there as well for sure, but I wanted to get a feel
> for any preference within this community that would be implementing and
> dealing with this spec on the other side. What do your libraries support
> for ECDSA and EdDSA inputs and outputs? Do you have a strong feeling on
> either of these choices?
> >>
> >> Thanks,
> >>  — Justin
>
>
Received on Friday, 14 January 2022 18:23:03 UTC

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