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Substitution Cipher Solver

Monoalphabetic substitution cipher with interactive solving assistant, drag-and-drop alphabet mapping, frequency analysis, bigram/trigram patterns, and word pattern finder.

Plain
A
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A
Cipher
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B
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B
Cipher
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C
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C
Cipher
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D
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D
Cipher
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E
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E
Cipher
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F
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F
Cipher
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G
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G
Cipher
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H
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H
Cipher
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I
↓
I
Cipher
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J
↓
J
Cipher
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K
↓
K
Cipher
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L
↓
L
Cipher
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M
↓
M
Cipher
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N
↓
N
Cipher
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O
↓
O
Cipher
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P
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P
Cipher
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Q
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Q
Cipher
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R
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R
Cipher
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S
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S
Cipher
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T
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T
Cipher
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U
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U
Cipher
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V
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V
Cipher
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W
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W
Cipher
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X
↓
X
Cipher
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Y
↓
Y
Cipher
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Z
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Z
Cipher

About Substitution Ciphers

How It Works

A substitution cipher replaces each letter with another letter according to a fixed rule. The key is a rearranged alphabet where position determines the substitution.

For example, with key "ZEBRACDFGHIJKLMNOPQSTUVWXY": A→Z, B→E, C→B, etc. This creates 26! (403 septillion) possible keys.

Cryptanalysis Techniques

  • Frequency Analysis: E, T, A are most common in English
  • Pattern Words: Short words like THE, AND, FOR are easy to identify
  • Bigrams/Trigrams: TH, HE, THE appear frequently
  • Word Boundaries: Single-letter words are usually A or I

Historical Use

Substitution ciphers have been used for thousands of years. Julius Caesar used a simple version (Caesar cipher). Mary Queen of Scots was convicted partly due to her substitution cipher messages being broken.

Security Note

Monoalphabetic substitution ciphers are easily broken with frequency analysis. They should never be used for real security. This tool is for educational purposes only.

Related Cipher Tools

Caesar Cipher
Simple shift cipher with auto-crack
Vigenère Cipher
Polyalphabetic cipher with key analysis
XOR Cipher
Binary encryption tool
ROT13 Cipher
Caesar cipher with shift 13

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Frequently Asked Questions

Common questions about the Substitution Cipher Solver

A monoalphabetic substitution cipher replaces each letter with another letter consistently throughout the message. Unlike Caesar cipher which shifts all letters by the same amount, a substitution cipher can use any mapping (A→Q, B→X, C→M, etc.). This creates 26! possible keys.

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