Tool for automatic Shift Cipher that consists in replacing a letter by another one in the alphabet using a shifting system, a basic or complex sequence of numbers.
Shift Cipher - dCode
Tag(s) : Substitution Cipher
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The shift cipher is a cryptographic substitution cipher where each letter in the plaintext is replaced by a letter a certain number of positions further down the alphabet. This number of positions is sometimes called a key.
The Caesar code is the most well-known shift cipher, usually presented with a shift key of value 3.
The shift cipher encryption uses an alphabet and a key (made up of one or more values) that shifts the position of its letters.
A letter in position $ N $ in the alphabet, can be shifted by $ X $ into the letter located at position $ N+X $ (This is equivalent to using a substitution with a shifted alphabet).
Example: Take the letter E in position 5 in the alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ, it will be encrypted by a shift of 3 in position 8 or H.
If the shifted position exceeds the number of letters in the alphabet, then take it at the beginning (imagine the alphabet as cyclical)
Example: Z shifted by 1 gives A.
Traditional shift encryption only applies to the 26 letters of the alphabet. For numbers or special characters, it is possible to change the alphabet or leave them unchanged.
It is possible to define different types of shifts, some shifts correspond to known encryption algorithms:
A single shift (all letters are shifted by the same value) is called Caesar Code.
A multiple shift, according to a sequence or a key that is repeated (the letters are shifted from each of the key values), is called Vigenere Cipher.
A mathematical shift, the easier is progressive, shifting the nth letter of the value n is the Trithemius Cipher or if the shift is more complex Affine Cipher or even Hill Cipher.
In addition, each offset can be applied to a single or several letters, to a single or several words, etc.
Decryption requires knowing the shift used and the alphabet.
Take a letter in position N in the alphabet that has been encrypted by a shift of X, it must be shifted by -X to return to its original position N-X.
Example: The letter H in position 8 in the alphabet ABCDEFGHIJKLMNOPQRSTUVWXYZ, will be decrypted from a shift of 3 in position 8-3=5 or E.
Example: The word TIJGU is decoded with an offset of 1 as SHIFT
The shift cipher can take a date as key (called date shift cipher), generally in the formats YYYYMMDD is used as it contains a series of 8 digits which can be used as the shift key.
Example: DATECODE encrypted with the date 2020/10/10 or (2,0,2,0,1,0,1,0) becomes FAVEDOEE
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Shift Cipher on dCode.fr [online website], retrieved on 2024-10-05,