Bacon's Cipher
Binary encoding in 1605 — Francis Bacon hid messages in the typeface itself
Pattern recognition · Statistical analysis of A/B distribution
Why This Matters
Francis Bacon’s cipher — devised by 1605 and fully described in his 1623 De Augmentis — was one of the earliest documented uses of binary encoding — representing each letter as a 5-bit sequence over two centuries before Boolean algebra and three centuries before digital computing.
Sir Francis Bacon described his cipher in De Augmentis Scientiarum (1623). Each letter of the alphabet is represented by a 5-bit binary sequence using only two symbols (A and B). Bacon's original application was steganography: hide a secret message within an innocuous text by printing the covering text’s letters in two distinguishable typefaces — for example, roman and italic in a teaching illustration. Bacon’s proposal used two alphabets with subtler differences.
Bacon’s two-symbol alphabet is an early documented example of binary representation. Its historical interest does not establish a direct line of invention to Boolean algebra or electronic computing.
Bacon's binary alphabet: A = AAAAA N = ABBAA B = AAAAB O = ABBAB C = AAABA P = ABBBA D = AAABB Q = ABBBB E = AABAA R = BAAAA ... Z = BBAAA Example: HI = AABBB ABAAA (each letter = 5 A/B symbols) Following the common modern convention (Bacon's own alphabet had 24 letters, merging U/V as well), I and J share the same code ABAAA (a 25-letter alphabet). Steganographic use: Normal text: AABBB ABAAA Hidden in cover text by using two fonts: normal=A, italic=B across 10 characters
As a pure cipher, Bacon is trivially broken — it's a fixed binary encoding of the alphabet. As steganography in printed text, detection requires identifying two typefaces, which is usually obvious with magnification. Modern steganography detection uses statistical analysis of pixel distributions or bit-level patterns.
| Concept from Bacon's Cipher | Modern Evolution |
|---|---|
| 5-bit binary alphabet (A/B) | ASCII: 7-bit binary encoding of 128 characters; UTF-8: variable-width binary |
| Two-symbol encoding | Binary notation also uses two symbols; this similarity does not establish direct historical descent |
| Steganographic application | Modern steganography: hiding data in image LSBs, audio files, network timing |
| Exhibit | 33 of 172 |
| Era | 1605 |
| Trust | Broken |
| Inventor | Sir Francis Bacon |
| Year | 1605 |
| Key Type | 5-bit binary (A/B patterns) |
| Broken By | Pattern recognition · Statistical analysis of A/B distribution |
Sources and Reading
The Codebreakers: The Comprehensive History of Secret Communication from Ancient Times to the Internet, David Kahn (revised edition, 1996), “The Pathology of Cryptology”: Bacon’s 1605 allusion,1623 description,24-letter alphabet and two typefaces. The museum’s 25-letter mapping is a stated modern variant.