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Mono-alphabetic Substitution

Tool to decrypt monoalphabetical substitution and find each letter of a substituted message with a deranged alphabet (monoalphabetic cipher).

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Mono-alphabetic Substitution -

Tag(s) : Substitution Cipher

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Mono-alphabetic Substitution

Monoalphabetic Substitution Decoder

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Decryption method




Monoalphabetic Substitution Encoder




See also: Caesar Cipher

Custom Deranged Alphabet Generator

Tool to decrypt monoalphabetical substitution and find each letter of a substituted message with a deranged alphabet (monoalphabetic cipher).

Answers to Questions

How to encrypt using an alphabetical substitution?

The monoalphabetical substitution consists in using a mixed alphabet (with the letters in an unusual order) and replacing the letters of the alphabet normal by it.

Example: NBAJYFOWLZMPXIKUVCDEGRQSTH is a totally random alphabet with the 26 letters of the Latin alphabet.

To understand, write the alphabet over the classic alphabet:

Plain alphabetABCDEFGHIJKLMNOPQRSTUVWXYZ
Substitution alphabetNBAJYFOWLZMPXIKUVCDEGRQSTH

The substitution involves a replacement the plaintext of all the letters of the first row with the letters associated with the second row.

Example: All A become N, all the B remain B, all the C become A, etc.

Example: With this substitution DCODE is encrypted as JAKJY.

Any deranged alphabet can be used to create a single alphabetical substitution (the same letter can be used only once in the alphabet).

How to decrypt using an alphabetical substitution?

Decryption requires knowing the alphabet mixed used and the inverse substitution encryption.

Substitution AlphabetNBAJYFOWLZMPXIKUVCDEGRQSTH
Plain AlphabetABCDEFGHIJKLMNOPQRSTUVWXYZ

The substitution involves replacing in the ciphertext all the letters of the first row with the letters associated with the second row.

Example: The encrypted message JAKJY has for plain message DCODE.

How to recognize a mono alphabetical substituted text?

The ciphered message has an index of coincidence identical to the language of the plain text.

English speakers call this encryption aristocrat (if there are spaces) or patristocrat (if there are no spaces between words).

How to decipher a substitution without the alphabet?

The interactive tool provided by dCode allows a semi-automatic decryption of messages encrypted by substitution ciphers.

The main technique is to analyze the frequencies of letters and find the most likely bigrams.

The known plaintext attack makes it possible to deduce some letters of the alphabet via the knowledge or the preliminary guess of certain portions of the plain text.

Example: The most common alphabets used for substitutions are: AZERTYUIOPQSDFGHJKLMWXCVBN
NBVCXWMLKJHGFDSQPOIUYTREZA
QWERTYUIOPASDFGHJKLZXCVBNM
MNBVCXZLKJHGFDSAPOIUYTREWQ
AQWZSXEDCRFVTGBYHNUJIKOLPM
ZYXWVUTSRQPONMLKJIHGFEDCBA
'AEIOUYBCDFGHJKLMNPQRSTVWXZ

What are the variants of the substitution cipher?

First, some substitution use specific alphabets, as Atbash that takes the alphabet backwards ZYXWVUTSRQPONMLKJIHGFEDCBA or the Caesar cipher which uses a shifted alphabet DEFGHIJKLMNOPQRSTUVWXYZABC that is shifted by 3. Then there are substitutions that use several alphabets, such as alphabet that changes depending on an algorithm defined by encryption (e.g. Vigenere uses 26 alphabets).

In game-play journals, substitution games / exercises are often called cryptograms.

Source code

dCode retains ownership of the online 'Mono-alphabetic Substitution' tool source code. Except explicit open source licence (indicated CC / Creative Commons / free), any algorithm, applet or snippet (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or any function (convert, solve, decrypt / encrypt, decipher / cipher, decode / encode, translate) written in any informatic language (PHP, Java, C#, Python, Javascript, Matlab, etc.) no data, script or API access will be for free, same for Mono-alphabetic Substitution download for offline use on PC, tablet, iPhone or Android !

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