On Jun 28, 2014, at 5:20 AM, MFPA <2014-667rhzu3dc-lists-gro...@riseup.net> 
wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA512
> 
> Hi
> 
> 
> On Friday 27 June 2014 at 11:35:00 PM, in
> <mid:a2f8dba9-1da7-47a6-bc79-cfaea3b02...@jabberwocky.com>, David Shaw
> wrote:
> 
> 
>> Incidentally, since subkeys have come up in this
>> thread, I seem to recall a few strange bugs with 8.x
>> (8.0? 8.1?) that make it difficult to use if the key
>> you are encrypting to has a signing subkey.  8.x didn't
>> always handle signing subkeys properly, so could end up
>> failing to encrypt (it wasn't 100% of the time - it
>> depended on which subkey was dated first).  If anyone
>> is curious, I'll dig out my notes for this.  I
>> submitted the bug to PGP, and I know it was fixed in a
>> later version.
> 
> 
> My recollection is that PGP 8.x would always try to encrypt to the
> newest subkey, and encryption would fail if the newest was a signing
> subkey. I had 8.0.3 and 8.1; if memory serves, both had this issue -
> signing subkeys were fairly new at the time.

Yes, that was it.  It got particularly strange when someone was using an RSA 
signing subkey or auth key (as they would do if they had a smartcard).  In that 
case, the PGP encryption would actually succeed (after all, RSA is capable of 
it, despite what the key flags instructed for use) but the GnuPG recipient 
would be unable to decrypt as from their perspective, that key was sign or auth 
only.

I put a limited workaround in GnuPG at the time - that's why the encryption key 
is always written to the card after the auth key (so the encryption key would 
always be the "newest".  Of course, that didn't handle existing keys.  The real 
fix was needed in PGP, and it was fixed.

David


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