CIPHER/SUBSTITUTION CIPHERS

Substitution ciphers

Each character is replaced by another character or symbol. The alphabet is renamed, not rearranged.

Atbash folds the alphabet in half and glues A to Z, B to Y, C to X. There is no key at all — knowledge of the method is the whole…

ZMWGSVOLLNRHGSVPVB…

Francis Bacon's 1605 biliteral cipher is the first recorded binary encoding of an alphabet, three centuries before anyone had a…

BAABA AABBB AABAA ABABA ABBAB ABBAB ABABB BAAA…

A book cipher replaces the alphabet with a book. Every letter is written as a position — page, line, word, letter — and the…

1 2 3 29 11 11 19 8 3 3 20 21 6 1 21 11 12 13 …

The oldest alphabet cipher most people meet first: every letter moves a fixed number of places down the alphabet. It takes about…

WKHROGORRPQHYHUVWRSV…

A nomenclator is half cipher, half dictionary. It substitutes letters as usual but also assigns its own codes to the names that…

01 / 03 / 02 / 01 / 04…

A null cipher does not disguise a letter — it hides which letters are the message. Every character in the transmitted text is a…

THEWL ATHEO HOLDO FAIRM NDTHS OLDBK ASSLE OMKE…

Pigpen writes letters as fragments of a grid. Two tic-tac-toe frames and two X frames give exactly 26 cells, so the cipher fits…

N3 N5 S3 S3 E1 N8 S6 S3 N4 E1 N5 N3 S9 N5 E2 E…

Playfair was the first practical cipher to encrypt letter *pairs* rather than single letters, and that one design decision bought…

JSVSGTIYCFTNQIXH…

Polybius did not invent a cipher. He invented a *notation*: a way to write any letter as two numbers between one and five. That…

32 35 35 33 34 15 52 15 43 44 45 35 41 44…

Before ciphers abbreviated letters, they abbreviated *words*. Tironian notes were a Roman shorthand of several thousand signs…

[THE] (SCRIBE) (WROTE) [CON] [AND] [EST] (IN) …