Crypt::Dining - The Dining Cryptographers' Protocol

            my $dc = new Crypt::Dining(
                    LocalAddr       => '',
                    Peers           => [ '', ... ],
            my $answer = $dc->round;
            my $answer = $dc->round("hello");

    The dining cryptographers' protocol is documented in Bruce Schneier's
    book as a kind of "cryptographic ouija board". It works as follows:

    A number of cryptographers are dining at a circular table. At the end of
    the meal, the waiter is summoned and asked for the bill. He replies,
    "Thank you, sir. The bill has been paid." The cryptographers now have
    the problem of working out whether someone at the table paid the bill,
    or whether the NSA has paid it as some sort of veiled threat. The
    protocol proceeds.

    Each cryptographer flips a coin, and shows the result ONLY to the
    participant on his RIGHT. Each cryptographer then compares his coin with
    that on his LEFT, and raises his hand if they show different faces. If
    any participant paid the bill, he "cheats" and does the opposite, that
    is, he raises his hand if the coins show the same face. Now, the hands
    are counted. An odd number means that someone at the table paid the
    bill. An even number means that the NSA paid.

    At most one person "cheats" at any time, otherwise the message is
    scrambled. Detecting scrambling is only possible with multi-bit messages
    containing a checksum.

    The comparison operator described above is the XOR operator on
    single-bit values. If the protocol is performed with multi-bit messages,
    then the XOR is still used.

    The following description is copied from
    <> and is
    redistributed under the GNU Free Documentation License. It is a very
    slightly different protocol to that implemented here, but the result is
    the same.

    The dining cryptographers protocol is a method of anonymous
    communication. It offers untraceability of both the sender and the

    The method is as follows: two or more cryptographers arrange themselves
    around a circular dinner table, with menus hiding the interaction of
    each pair of adjacent cryptographers from the rest. Each adjacent pair
    picks a random number in private. Then each cryptographer announces
    publicly the difference between the number on his right and the number
    on his left, adding a message if he wants to transmit one. All
    cryptographers then add up the publicly announced numbers. If the sum is
    0, no one sent a message. If the sum is a valid message, one
    cryptographer transmitted a message. If the sum is invalid, more than
    one cryptographer tried to transmit a message; they wait a random time
    and try again.

    If the send_*() and recv_*() methods are overridden to use TCP sockets
    with very large messages, deadlock may occur around the ring unless
    something intelligent is done with select().

    Crypt::Chimera - another cryptographic curiosity.

    Copyright (c) 2005 Shevek. All rights reserved.

    This program is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself.