Just a thought

[David Shaw]

On Apr 25, 2009, at 6:14 PM, John Clizbe wrote:

> Ingo Klöcker wrote:
>> On Saturday 25 April 2009, John Clizbe wrote:
>>>
>>> The message will be encrypted once with a symmetric cipher and
>>> session key. Then the session key is encrypted to each recipient's
>>> public key and the encrypted session keys are attached to the
>>> message.
>>>
>>> For each recipient the first valid key with matching email address  
>>> is
>>> the one selected. If this is not the preferred key, then Enigmail's
>>> Per-recipient rules may be setup to specify the correct key to use.
>>
>> How does Thunderbird/Enigmail handle bcc'd recipients? Does it create
>> several differently encrypted copies of the message in case of bcc'd
>> recipients, i.e. one copy of the message encrypted with the keys of  
>> all
>> public recipients and additional copies of the message (one per bcc'd
>> recipient) encrypted only with the key of the corresponding bcc
>> recipient (and probably with the sender's key)?
>
> Enigmail passes GnuPG a list of recipients to encrypt to. It does not
> generate separate messages, only the one.  This is a constraint of
> Thunderbird's architecture.
>
> BCCed recipients are treated as just another recipient. There is only
> one copy of the message and one set of encrypted session keys.

I'm not sure if Enigmail has sufficient control here (due to the  
Thunderbird restrictions), but if possible, it might be wise to handle  
Bcc's recipients with --hidden-recipient instead of --recipient (i.e.  
"-r").  That would better duplicate the standard expectations of a  
user using Bcc: the regular recipients can all see who the recipients  
are, but not the Bcc'd people.  As things stand now, any recipient can  
see who was Bcc'd, which sort of removes the "B" from the Bcc.

--throw-keyids is a reasonable solution as well, but it's more of a  
sledgehammer, rather than a scalpel.

David