Cryptogram

Break the substitution cipher and recover the quotation.

What it is

A short text — here, a public-domain quotation — enciphered by a consistent letter-for-letter substitution: every A in the plaintext became the same cipher letter, and no letter stands for itself. Punctuation, spacing and word breaks survive, which is what makes it solvable with a pencil.

How to play

One-letter words are A or I. The most frequent cipher letter is probably E, T, A or O; a frequency table (this crate prints one as an aux block) makes that concrete. Apostrophe patterns give T, S and N’T; double letters narrow fast (LL, EE, SS, OO). Guess a common short word, propagate its letters everywhere, and abandon the guess at the first contradiction — the cascade either confirms itself in a few words or collapses.

Purpose

The only text puzzle in the catalogue, and the one that trades on curation: the corpus must be genuinely public-domain (pre-1929 or explicitly so), and quote selection is the product. In the workspace it also demonstrates a correctness property that looks like decoration and is not: the cipher is a true derangement, because a letter mapping to itself hands out free letters.

History

Substitution ciphers are ancient (Caesar’s shift, the Hebrew atbash), but the parlor puzzle dates to the 19th century — Edgar Allan Poe stoked the vogue and built “The Gold-Bug” (1843) around frequency analysis. The American Cryptogram Association (1929) standardised the hobby form it still has.

This implementation

• Spec knobs: corpus/quote selection, hints, difficulty.
• Generation: a random derangement of the alphabet (no fixed points — built deranged in one pass, not by rejection) applied to a corpus quote; optional starter hints; a letter-frequency table shipped as an aux scene.
• Guarantees: the derangement property is tested for every seed; hint letters are verified against the key; the corpus is public-domain by construction.
• Difficulty: quote length, letter-frequency flatness, and how many one- and two-letter words are exposed, banded.