[Privacy-pass] RFC 4055 PSS encoding

[Watson Ladd <[e-mail]>]

Dear privacy pass WG,

As a result of some events we've discovered that draft-10 of the
privacy pass protocol is not compatible with RFC 4055's recommendation
to encode NULLs explicitly when serializing RSA PSS parameters.

Unfortunately much software including OpenSSL 3.0 and the Go standard
library include these NULLs when serializing RSA PSS public keys. This
makes it difficult to use these packages in implementation.

I think the simplest way to fix this issue is to take the token ID as
the hash of the DER encoding as presented in the directory, and follow
RFC 4055 for tolerance.

Apologies for not spotting this issue during last call.
Sincerely,
Watson

-- 
Astra mortemque praestare gradatim