subst

package
v0.7.0 Latest Latest
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 Go to latest Published: Jul 14, 2026 License: Apache-2.0 Imports: 3 Imported by: 0

Documentation

Overview

Package subst solves monoalphabetic substitution ciphers by hill-climbing over the 26! key space, scored by an embedded English n-gram model. It seeds from a frequency match and refines with random key-swaps under random restarts — the standard approach for this class of cipher.

Index

Constants

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Variables

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Functions

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Types

type Key 

type Key [26]byte

Key is a substitution key: Key[c] is the plaintext letter index (0..25) for ciphertext letter index c. It is always a permutation of 0..25.

func Solve 

func Solve(ct []byte, m *lang.Model, r *rand.Rand, opt Options) (Key, []byte, float64)

Solve recovers the most English-like substitution key for ct using model m and randomness r. It returns the best key, its decryption, and its score.

func (Key) Decrypt 

func (k Key) Decrypt(ct []byte) []byte

Decrypt applies the key, preserving case and passing non-letters through.

type Options 

type Options struct {
	Restarts int // independent hill-climbs (default 25)
	MaxFails int // consecutive non-improving swaps before a restart ends (default 1500)
}

Options tune the search. Zero values get sensible defaults.

Source Files

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