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Baudot / ITA2 (5-bit)

From the Buttcrack Cipher Wiki — the free field guide to classical ciphers

Baudot / ITA2 (5-bit) — Five bits per character on teleprinter tape, in the ITA2 letter table.

Five bits per character, ITA2 letters table. Distinguished from Bacon by its own letter assignment.

A worked example§

Encrypting a sample with the cipher itself, at build time:

MEET ME BY THE OLD CLOCK TOWER AT DAWN

No key — the transformation is fixed.

produces the ciphertext

00111 10000 10000 00001 00100 00111 10000 00100 10011 10101 00100 00001 00101 10000 00100 00011 01001 10010 00100 01110 01001 00011 01110 11110 00100 00001 00011 11001 10000 01010 00100 11000 00001 00100 10010 11000 11001 00110

This example is generated by running the cipher when the page is built, and the round trip is checked, so it always matches what the solver does.

How it is broken§

A five-bit stream is also valid Bacon, so both tables are decoded and the one that reads as English wins.

History and context§

Emile Baudot's 1870 code, later revised by Donald Murray, is why 'baud' is a unit — and it is the tape that fed the Lorenz machine, whose traffic Bletchley called Tunny.

See also§

Morse code · Bacon cipher · Bacon (letter case) · A1Z26 (numbered alphabet) · Polybius square · Tap code

Browse every cipher in the Codes and alphabets family, read the history of codebreaking, or return to the wiki main page.

Frequently asked questions§

How is the Baudot / ITA2 (5-bit) broken?

A five-bit stream is also valid Bacon, so both tables are decoded and the one that reads as English wins.

What key does the Baudot / ITA2 (5-bit) use?

none. There are 1 possible keys.

How much ciphertext do I need?

At least 15 characters for this solver to attempt it; short messages can be readable and still not be proof.

Can I break a Baudot / ITA2 (5-bit) on this page?

Not with the browser build, which targets the common puzzle families. The desktop version searches it: see the Windows app page.

Categories: Codes and alphabets | Full-version ciphers | Cipher wiki
The facts in this article are generated from buttcrack's cipher registry when the site is built, so they describe the implementation you can run on this page. Registry-generated content is checked against the code; the history is editorial.

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