Tag

#Quadgram Statistics

2 articles with this tag.

A visual representation of the four-square cipher breaker recovering two key squares

Basic Classic Symmetric Breakers Advanced

Breaking the Four-Square Cipher with Two Key Squares

The four-square cipher hides letter frequencies behind two keyed grids, but it is still a pencil-and-paper cipher. Learn how simulated annealing with quadgram statistics recovers both secret squares from the ciphertext alone, with runnable Python.

Oct 29, 2026 14 min read

Basic Classic Symmetric Breakers Advanced

Breaking the Playfair Cipher

Playfair defeated single-letter frequency analysis by encrypting pairs of letters through a 5×5 key square. But the same simulated-annealing idea that cracks the substitution cipher still works here too, once you swap in quadgram statistics and a richer set of moves.

Aug 22, 2026 20 min read

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