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Announcing: First-ever collection of declassified Chaocipher-related correspondences

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Oct 6, 2009, 7:33:51 AM10/6/09

The "Chaocipher Clearing House" is a web site dedicated to tracking
cryptanalytic work related to solving John F. Byrne's Chaocipher. The
site can be found at


Cryptologic books and texts that mention John F. Byrne's Chaocipher
(e.g., David Kahn's "The Codebreakers", articles in Cryptologia) refer
tantalizingly to historical letters between Byrne and William F.
Friedman, the father of American cryptology. The only letters readers
have had access to are snippets quoted by Byrne in his autobiography,
"Silent Years". The full correspondences between Byrne and Friedman,
unfortunately, have not been readily available to the cryptologic

As of today, this is no longer the case.

The Chaocipher Clearing House is proud to present a first-ever
comprehensive collection of Chaocipher-related correspondences between
John F. Byrne, William F. Friedman, and other persons.

Thanks to numerous Chaocipher researchers in the past, these letters
have been assembled from numerous sources, including declassified
Freedom Of Information Act (FOIA) requests to NSA, private
collections across the United States, and John F. Byrne's own
autobiographical "Silent Years".

Reading these letters will give you an unprecedented historical
perspective on the intriguing cipher mystery called Chaocipher.

The collection can be found at:


If you've never tackled the Chaocipher challenge, you'll find all the
resources you need to start with on the Chaocipher Clearing House site
(http:// If you've done any
work in the past on Chaocipher, how about sharing your thoughts with
the community? Collaborative work has a tendency to snowball. Come
aboard and be part of the joint effort.

Comments, informational contributions, and suggestions are most
welcomed. Feel free to contact me at the Chaocipher Clearing House

Moshe Rubin

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