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Substitution Cipher

Tool to encrypt / decrypt a message by substitution cipher (all sizes) by replacing one or more characters with one or more others

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Substitution Cipher -

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# Substitution Cipher

## Guide for Substitution

The most common method of substitution replaces the 26 letters of the alphabet (one letter matches only one other). dCode has a dedicated tool for this:

### Symbols Substitution

When the substituted characters are symbols/glyphs/drawings, this page cannot be used but dCode has tools for that:

## Substitution Decoder

Auto fill: [A-Z] [A-Z0-9] [A-Za-z0-9]

## Substitution Encoder

Auto fill: [A-Z] [A-Z0-9] [A-Za-z0-9]

### What is a substitution cipher? (Definition)

Substitution encryption consists, as its name suggests, of substituting (replacing) one element with another. In the case of a text, it is a question of replacing the characters (often letters) of the message by others.

### How to encrypt using substitution cipher?

For a substitution to be correct, it is necessary for the same element to be substituted by only one other (valid in both cases, for encryption and decryption) so that there is never more than one possibility of encryption or decryption.

Example: The Caesar cipher is an alphabetical substitution which replaces each letter by the following in the alphabet: ABC becomes 'BCD'

### How to decrypt substitution cipher?

The condition for a successful substitution decryption is to know the correspondence lookup table used.

### How to recognize a substitution ciphertext?

If the substitution is a simple transcription, then the frequency analysis can quickly recognize the language of the plain message.

If the substitution is more complex, it may become impossible to recognize the encryption.

The notions of substitutes, replacements and changes are clues.

### What are the variants of the substitution cipher?

Substitution cipher is one of the most basic cryptography methods. Many variations are possible:

— Ciphers by mono-alphabetic substitution, with a disordered alphabet, one letter replaces another.

— Encryptions by poly-alphabetic substitution, with several alphabets.

— Encryptions by homophonic substitution, the same element can be substituted by several others.

— Substitution by dictionary, with words, n-grams substituted by others.

### When was substitution cipher invented?

It is likely that substitution encryption appeared short after the invention of writing.

## Source code

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Substitution Cipher on dCode.fr [online website], retrieved on 2024-09-14, https://www.dcode.fr/substitution-cipher

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