Encryption to key with multiple subkeys

[Peter Pentchev]

On Wed, May 12, 2010 at 02:59:44AM +0200, Joke de Buhr wrote:
> On Wednesday 12 May 2010 02:08:27 Daniel Kahn Gillmor wrote:
> > yup, i think this is a good argument for your proposed behavior.  what i
> > haven't seen yet (haven't thought through yet) is what the
> > counter-arguments might be.
> 
> One possible argument against it could be the increased size of the encrypted 
> message. But the size of an email isn't that important nowadays and if size 
> matters the user should set a compression (bzip2) algorithm within the key 
> settings.

Just for the record: no, the encrypted message will not be much larger.

The way OpenPGP encryption works is that a new, random, once-only
session key is generated each time you want to encrypt a message to one
or more recipients; the message itself is encrypted using a symmetric
algorithm, and only the session key is encrypted using the asymmetric
algorithm specified by the users' OpenPGP encryption keys.  Thus, only
the session key (a couple of hundred bytes at most, and usually just
a couple of dozens of bytes) will be encrypted over and over again
for each recipient's encryption key - and, in the case discussed, for
each encryption subkey of each recipient's key.

Well, of course, if you're encrypting a single-byte message,
the overhead might be detectable... :)

G'luck,
Peter

-- 
Peter Pentchev	roam at ringlet.net    roam at space.bg    roam at FreeBSD.org
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If the meanings of 'true' and 'false' were switched, then this sentence wouldn't be false.
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