Re: [openpgp] [openpgp-email] Keyserverless Use of OpenPGP in Email

["Neal H. Walfield" <[e-mail]>]

On Tue, 12 Apr 2016 15:49:18 +0200,
Simon Josefsson wrote:
> > I'd like to discuss a thought that has come up in my work on k9 mail:
> > Using OpenPGP in E-Mail without relying on keyservers. 
> 
> Important use-case.
> 
> > If we don't have bandwidth constraints, we can solve this by sticking
> > the public key block right next to every signature we make, which
> > effectively eliminates the need for keyservers (with the possible
> > exception of the distribution of revocation certs).  However, it also
> > adds ~10kb of size to every signature.  This is a rather extreme
> > approach, and although 10kb are not a lot these days, they add up.
> 
> Not necessarily -- I don't think you have to add all signatures to the
> key for this use-case to work, do you?  If you just include a stripped
> public key, verification of the signature will work.  It should be max
> 1-2kb I would guess.

I think 10kb is accurate.  If you have a primary and three subkeys and
all four have a self-signature, then you are about 10k:

  $ gpg2 -k 0xAACB3243630052D9
  pub   rsa3744/0xAACB3243630052D9 2015-04-07 [SC] [expires: 2025-04-04]
        Key fingerprint = 8F17 7771 18A3 3DDA 9BA4  8E62 AACB 3243 6300 52D9
  uid                   [ultimate] Neal H. Walfield <[e-mail]>
  uid                   [ultimate] Neal H. Walfield <[e-mail]>
  uid                   [ultimate] Neal H. Walfield <[e-mail]>
  sub   rsa2048/0x7223B56678E02528 2015-04-07 [S] [expires: 2017-04-06]
  sub   rsa2048/0xC2B819056C652598 2015-04-07 [E] [expires: 2017-04-06]
  sub   rsa2048/0xA3506AFB820ABD08 2015-04-07 [A] [expires: 2017-04-06]
  $ gpg2 --export-options=export-minimal --export 0xAACB3243630052D9 | wc -c
  9622

Of course, we can leave off the authorization key in this case.  But,
we need the primary key to verify the self-signatures, we need to the
signing key to verify signatures and we need the encryption key to
encrypt.  So, this is pretty minimal.

:) Neal