Subject: Re: Signature calculation language

From: Jon Callas <[email-masked]>
Date: Tue, 18 Apr 2006 11:59:32 -0700

On 12 Oct 2005, at 6:55 AM, Werner Koch wrote:

>
> On Tue, 11 Oct 2005 22:50:34 -0400, David Shaw said:
>
>> I support making 0x19 backsigs a MUST.
>
> I concur with David.  I am actually a heavy user of signing subkeys
> because they allow to keep the primary key offline.
>

Section 10.1 says:

    Each Subkey packet MUST be followed by one Signature packet, which
    should be a subkey binding signature issued by the top level key.
    For subkeys that can issue signatures, the subkey binding signature
    MUST contain an embedded signature subpacket with a primary key
    binding signature (0x19) issued by the subkey on the top level key.

And I think this does make it a MUST.

If there should be anything else (or this is wrong, unclear, etc.),  
just let me know.

	Jon

---

From: Jon Callas <[email-masked]>
Date: Tue, 18 Apr 2006 12:09:42 -0700

> because they allow to keep the primary key offline.

I also added an implementation nit:

    The 0x19 back signatures were not required for signing subkeys  
until relatively
    recently. Consquently, there may be keys in the wild that do not  
have these back
    signatures. Implementing software may handle these keys as it  
sees fit.

	Jon