Classic Protocol + Manoj

Versão em Português

0. Variant

This variant of the Classic Protocol with Rotation adds secrets for key verification, as idealized by Manoj Srivasta. It's not widely adopted for being even slower than the first and is undoubtfully only suited for small 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 and secrets 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.

In this moment, also, each person must think in a secret (preferably unique for each interaction). Each one writes the shared secrets (Secrets 1 and 2) in the piece of paper corresponding to the key to be signed.

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 that were given to you by the participants during the party you must:

1. Create a new secret (Secret 3), different from the one you used with that person (Secret 1).
2. Send an email to that person, signed by your key, ciphered to that person, containing the secret you just created (Secret 3) and the secret the person told you (Secret 2).
3. The person must, then, create another secret (Secret 4), different from the one already told to you (Secret 2).
4. The person must send an email, signed by his own key, ciphered to you, containing the secret that was just created (Secret 4), the secret you told at the party (Secret 1) and the new secret you just sent (Secret 3).
5. When you get this email, you must check if both secrets you shared with that person (Secrets 1 and 3) match and take note of the newly created secret that person sent (Secret 4).
6. You must, then, sign that person's key, sending it back in a message signed by you, ciphered to that person, along with the new secret that person just sent you (Secret 4).
7. When that person got your email and check that Secret 4 matches, he should sign your key, sending it back to you, signed by his own key and ciphered to you.

-- PabloLorenzzoni - 08 May 2009