Re: [openpgp] v5 sample key

[Jonathan McDowell <[e-mail]>]

On Tue, Apr 23, 2019 at 10:28:26AM +0200, Werner Koch wrote:
> On Mon, 22 Apr 2019 08:55, [e-mail] said:
> > There is no distinction between V3, V4, and V5 signatures resp. keys.
> > However, GnuPG computes the hash in function hash_public_key() for V5
> > keys in a different way: starting with octet 0x9a and a four-octet
> > length is given before the body of key packet is hashed.
> 
> That is because 12.2 (Key IDS and Fingerprints) has
> 
>    A V4 fingerprint is the 160-bit SHA-1 hash of the octet 0x99,
>    followed by the two-octet packet length, followed by the entire
>    [...]
>    A V5 fingerprint is the 256-bit SHA2-256 hash of the octet 0x9A,
>    followed by the four-octet packet length, followed by the entire
> 
> I think it makes sense to keep the signature computation in sync with
> the fingerprint computation.  Using the four-octet length and thus 0x9a
> is important because it remove ambiguities if the key material is larger
> than 2^16.

A move to easily enable key material > 2^16 bytes seems to be in
conflict with dkg's work on trying to reinvigorate the usefulness of key
servers + the suggestion to limit key material packets to < 8383 bytes.

J.

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