Baconian Cipher — Bench tool

IWhat this tool does

Assign every letter a five-position pattern of two symbols. Bacon used A and B; the modern bench uses 0 and 1 for clarity. Here is the classical 24-letter version — I and J share a pattern, U and V share a pattern, because five binary positions give 32 slots and the Elizabethan alphabet needed only 24:

Now the trick. The five marks need not be letters at all. They can be two typefaces in a printed book: ordinary roman versus italic, large versus small, one font versus another. Bacon's own example was a printed text in which that distinction carried a hidden message that a reader would never notice, because the visible sentence was perfectly ordinary prose.

The bench writes the patterns out as literal A and B, which makes them visible for study but destroys the whole point. In real use, the marks are the invisible part and the prose is the visible part.

IIThe key

The mapping is fixed and public; Bacon published it. There is no key in the cryptographic sense at all.

The key is the cover text: whatever prose you choose to hide the marks in. That makes the space unbounded in the same unhelpful way as the null cipher earlier on this loom.

What Bacon actually contributed is the discovery of encoding capacity. Five binary positions carry 32 values, which is exactly enough for an alphabet plus a little slack, and the slack is where the I/J and U/V mergers come from. Every digital character encoding since — five-bit Baudot, seven-bit ASCII, eight-bit bytes, sixteen-bit Unicode — makes the same trade between capacity and redundancy.

The Baconian is the first cipher in this collection whose weakness is not in the algorithm but in the carrier.

IIIWhat it will not protect

Historical ciphers are for study and recreation and are not suitable for protecting real information. The full analysis is in the cipher entry.