Classic Protocol With Rotation

Versão em Português

0. Variant

This variant of the Classic Protocol adds a little bit of order to the chaos that usually happens in parties managed by it. Nevertheless, it's not suited to large parties.

1. Requirements

• A key pair.
• Two ids with recent photo (or, at least, closest to your look today), at least one of them issued by a governmental entity.
• Several copies of the fingerprint of your public key.
• A pen.

2. Before the Party

You'll need several printed copies of the fingerprint of your public key. Small pieces of paper with the output of the command:

bash$ gpg --fingerprint KeyID

...are, in general, all that's needed.

3. During the Party

Group distribution

In the party, participants will be divided in two groups lined up in front of each other (we'll call them "group A" and "group B").

Keys exchange

Every participant exchange the slips of paper containing the printed fingerprint with the other right in front. Every one is also responsible to check if given ID corresponds to the person and to the name in the slip of paper.

Rotation

• After the key exchange, in the first move all participants of the group A take a step to their left, while group B participants don't move. In this moment, a participant of each group will be left out of rotation at each end of the line.
• After new key exchange involving the participants in front of each other, occurs the second move, in which all participants of group B take a step to their left, while group A participants fon't move. In this moment, the participants that were left out of rotation previously join the opposite group.
• After a new key exchange, the process go back to the beginning. When all participants that began in group A end up in group B, the party is over.

In the following diagrams, all the rotations of a 8 participant party are depicted:

Moment 0:         group A:     1   2   3   4
                  group B:     5   6   7   8
=================================================> Exchange keys: 1-5, 2-6, 3-7, 4-8
Moment 1:         group A:         1   2   3   4
                  group B:     5   6   7   8
=================================================> Exchange keys: 1-6, 2-7, 3-8 / Left out: 5 and 4
Moment 2:         group A:     5   1   2   3
                  group B:     6   7   8   4
=================================================> Exchange keys: 5-6, 1-7, 2-8, 3-4
Moment 3:         group A:         5   1   2   3
                  group B:     6   7   8   4
=================================================> Exchange keys: 5-7, 1-8, 2-4 / Left out: 6 and 3
Moment 4:         group A:     6   5   1   2
                  group B:     7   8   4   3
=================================================> Exchange keys: 6-7, 5-8, 1-4, 2-3
Moment 5:         group A:         6   5   1   2
                  group B:     7   8   4   3
=================================================> Exchange keys: 6-8, 5-4, 1-3 / Left out: 7 and 2
Moment 6:         group A:     7   6   5   1
                  group B:     8   4   3   2
=================================================> Exchange keys: 7-8, 6-4, 5-3, 1-2
Moment 7:         group A:         7   6   5   1
                  group B:     8   4   3   2
=================================================> Exchange keys: 7-4, 6-3, 5-2 / Left out: 8 and 1
Moment 8:         group A:     8   7   6   5
                  group B:     4   3   2   1
=================================================> Party is over

4. After the Party

Key Signing

With the pieces of paper given to you by the other participants, you can choose the best way to sign the keys that you have correctly verified. This procedure is beyond the scope of this document (check how to sign automatically using caff or manually one by one the cryptographic keys).

What to do with the signed keys?

It's controversial whether you should send the signed keys to a public keyserver or back to its owner, so he/she do whatever he/she likes. It's generally considered Good Practice™ to send it back to its owner. This process can be rather slow and tedious if you've chosen to sign manually each key... Luckily, caff before mentioned follows this practice, and we recommend its use.

-- PabloLorenzzoni - 03 May 2009