Look closely at the text on this page. Now look closer. Beyond the words and their meanings, have you ever considered the letters themselves—their shapes, their fonts, their subtle variations—as a medium for a second, hidden message? In the 17th century, the polymath Sir Francis Bacon did more than just consider it; he systematized it, creating a brilliant method of steganography that stands as a testament to the idea that information can be encoded anywhere, even in the style of the text you’re reading right now.

This is Bacon’s Cipher, and it represents a fascinating intersection of typography, cryptography, and linguistics. It’s a forerunner to the binary systems that power our digital world, all cleverly disguised within the analog medium of the printed word.

What is Bacon’s Cipher? A Binary Beginning

At its heart, Bacon’s Cipher isn’t a traditional cipher that scrambles letters (like a substitution cipher). Instead, it’s a method of steganography—the art of hiding a message in plain sight. The goal is not just to make the message unreadable to outsiders, but to make them unaware that a message even exists.

Bacon, writing in his 1623 De Augmentis Scientiarum, proposed that any piece of information could be reduced to sequences of just two distinct elements. Let’s call them ‘a’ and ‘b’. Sound familiar? This is the fundamental principle of binary code, the language of modern computers (0s and 1s), conceived centuries before the first vacuum tube glowed to life.

He created a 5-bit binary code for each letter of the alphabet. In his original system, he used a 24-letter alphabet, combining I/J and U/V as was common at the time. A modern 26-letter version looks like this:

• A = aaaaa
• B = aaaab
• C = aaaba
• D = aaabb
• E = aabaa
• F = aababa
• G = aababb
• H = aabba
• I = aabbb
• J = abaaa
• K = abaab
• L = ababa
• M = ababb
• N = abbaa
• O = abbab
• P = abbba
• Q = abbbb
• R = baaaa
• S = baaab
• T = baaba
• U = baabb
• V = babaa
• W = babab
• X = babba
• Y = babbb
• Z = bbaaa

With this system, any secret message can be translated into a long string of ‘a’s and ‘b’s.

The Genius of Typography: Hiding the Code in a Carrier Text

Translating “SECRET” into `baaab aabaa aaaba baaaa aabaa baaba` is the easy part. The true genius of Bacon’s method lies in how this binary string is hidden. Bacon specified that you need a “carrier” text—any piece of writing that is at least five times longer than your secret message.

Each letter of the carrier text is then assigned an ‘a’ or ‘b’ value based on its typography. Bacon described using “two sorts of letters”, one in “Form A” and one in “Form B.”

This is where the system becomes incredibly flexible and subtle. The two forms could be:

• Roman vs. Italic
• Serif vs. Sans-serif
• A regular font vs. a bold font
• Two minutely different manuscript hands
• Even something as subtle as one font having slightly longer descenders (the tails on letters like ‘g’ and ‘p’) than the other.

As long as the two forms are visually distinct to the intended recipient, the code can be embedded.

An Example in Action

Let’s encode the secret message “HIDE” into a carrier text. For our two forms, we’ll use regular type (Form A) and italic type (Form B) to make it obvious.

Step 1: Convert the secret message to Baconian binary.

Using our chart:

• H = aabba
• I = aabbb
• D = aaabb
• E = aabaa

Our full binary string is: aabbaaabbbaaabbaabaa

Step 2: Choose a carrier text.

We need a text with at least 20 characters (4 letters x 5 bits/letter). Let’s use a fitting quote from Bacon himself: “Knowledge is power.” (18 characters). We’ll add a word to make it long enough: “True knowledge is power.” (23 characters).

Step 3: Embed the binary string into the carrier text.

We’ll go through the carrier text letter by letter, assigning each one a form based on our binary string. Regular type is ‘a’, and italic is ‘b’.

Secret binary: aabba aabbb aaabb aabaa

Carrier text: Truek nowle dgeis power

Let’s map them:

T r u e k  -> a a b b a -> T r u e k
n o w l e  -> a a b b b -> n o w l e
d g e i s  -> a a a b b -> d g e i s
p o w e r  -> a a b a a -> p o w e r

Step 4: Present the final, encoded text.

The resulting text would be printed to look like this:

Truek nowledge is power.

To an unsuspecting reader, this might look like a simple printing quirk or an aesthetic choice. But to someone who knows the system, it’s a perfectly legible message. They would simply transcribe the form of each letter into ‘a’s and ‘b’s, group them in fives, and decode the hidden word: HIDE.

The Shakespeare Controversy and Cultural Legacy

No discussion of Bacon’s Cipher is complete without mentioning the Baconian theory of Shakespeare authorship. This fringe theory posits that Sir Francis Bacon was the true author of Shakespeare’s plays and poems. Proponents, like Ignatius L. Donnelly, scoured the First Folios of Shakespeare’s work, claiming to find messages hidden using Bacon’s Cipher within the printed text, pointing to minute variations in the typefaces used.

While these claims have been thoroughly debunked by mainstream literary scholars and historians—the typographic variations are now understood to be common and random printing artifacts of the era—the theory cemented Bacon’s Cipher in the popular imagination. It transformed it from a mere cryptographic curiosity into a tool of grand literary conspiracy.

From Typography to Terabytes: An Analog Ancestor

What makes Bacon’s Cipher so profound from a linguistic and communication perspective is its manipulation of the medium itself. The carrier text has two layers of meaning: the explicit linguistic content (the words) and the implicit steganographic content (the typography). The writing system is doing double duty.

This is a powerful concept that resonates deeply in our digital age. Bacon’s method is a direct ancestor of modern digital steganography, where data is hidden within the “noise” of other files:

• A secret text file can be hidden in the least significant bits of the pixels in an image file.
• A clandestine message can be encoded in the background hiss of an audio track.
• Even today, messages can be hidden using zero-width characters in digital text, invisible to the human eye but readable by a computer program.

Sir Francis Bacon, with his ‘a’s and ‘b’s and his two forms of type, was demonstrating that any medium with the capacity for variation can be a medium for information. He saw that the how of writing could be just as meaningful as the what. It’s a humbling reminder that even in a simple line of text, there can be worlds of information hidden just beneath the surface, waiting for the right eyes to see it.