Re: MACs and Signatures (was Re: draft-ietf-httpbis-message-signatures-05)

A minor comment

> On 14 Jul 2021, at 11:19 PM, Watson Ladd <watsonbladd@gmail.com> wrote:
> 
> Which applications, what kind of switching? If it's identifying the
> key in the signed data, that can be done, but the algorithm must
> travel with the key, not the message. Why is indicating the algorithm
> in the signed data necessary? Could you please provide examples of
> applications that need it?

With MAC no key is sent. So you need somehow to indicate the MAC algorithm.