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Alphabetical Substitution

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

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Alphabetical Substitution -

Tag(s) : Cryptography, Substitution Cipher

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Alphabetical Substitution

Monoalphabetic Substitution Encoder

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

How to encrypt using an alphabetical substitution?

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

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

We can write the alphabet over the classic alphabet to better understand:

Plain alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ NBAJYFOWLZMPXIKUVCDEGRQSTH

The substitution involves replacing 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 Alphabet NBAJYFOWLZMPXIKUVCDEGRQSTH ABCDEFGHIJKLMNOPQRSTUVWXYZ

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

Example: Consider the encrypted message JAKJY, then the plain message is 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.

How to decipher a substitution without the alphabet?

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

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

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 substutition 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).

Source code

dCode retains ownership of the source code of the script Alphabetical Substitution. Except explicit open source licence (indicated Creative Commons / free), any algorithm, applet, snippet, software (converter, solver, encryption / decryption, encoding / decoding, ciphering / deciphering, translator), or any function (convert, solve, decrypt, encrypt, decipher, cipher, decode, code, translate) written in any informatic langauge (PHP, Java, C#, Python, Javascript, etc.) which dCode owns rights can be transferred after sales quote. So if you need to download the Alphabetical Substitution script for offline use, for you, your company or association, see you on contact page !

Team dCode read all messages and answer them if you leave an email (not published). It is thanks to you that dCode has the best Alphabetical Substitution tool. Thank you.

Source : http://www.dcode.fr/monoalphabetic-substitution
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