Bacon's cipher

create

create("bacon")

family

Fractionation

options

none

self-inverse

no

keyspace

1 (fixed 5-bit encoding)

try it

ciphers bacon "SECRET"

Francis Bacon's cipher writes each letter as five symbols from a two-letter alphabet, originally to hide a message in the italics of an innocent text. The historical alphabet has 24 letters, I and J merged, U and V merged. This one uses all 26 - A is AAAAA, B is AAAAB, Z is BBAAB - so the round trip is exact. No separators in the output. Decoding reads any A and B, ignores everything else, takes them five at a time.

const bacon = create("bacon");
bacon.encode("A").text; // "AAAAA"
bacon.encode("HI").text; // "AABBBABAAA"
bacon.decode("AABBB ABAAA").text; // "HI"

Puzzle uses the 24-letter version? Then I and J come out as one letter and U and V too. Map them by hand after decoding, it's two letters.