Function Repository Resource:

# CaesarDecipher

Decipher a Caesar-enciphered string

Contributed by: Sander Huisman
 ResourceFunction["CaesarDecipher"][string,n] deciphers a Caesar-enciphered string that was enciphered by shifting letters in string by n places further in the Latin alphabet. ResourceFunction["CaesarDecipher"][{s1,s2,…},n] deciphers each string si. ResourceFunction["CaesarDecipher"][n] represents an operator form of ResourceFunction["CaesarDecipher"] that can be applied to an expression.

## Details

ResourceFunction["CaesarDecipher"] replaces each plain text character with a different one a fixed number of places n up the alphabet. Here is an example for n=3, where the letter f is converted to the letter c: ResourceFunction["CaesarDecipher"][string] performs the ROT13 substitution.
n can be negative, shifting the letters to the right.
ResourceFunction["CaesarDecipher"] threads over the first argument.
Letters retain their case (lowercase/uppercase).

## Examples

### Basic Examples (2)

Perform a Caesar decipher with a shift of 2:

 In:= Out= Decipher a text by shifting the letters 9 positions back:

 In:= Out= ### Scope (3)

Cipher/decipher using a shift of n=13, also known at the ROT13 cipher:

 In:= Out= In:= Out= Decipher multiple strings:

 In:= Out= Create an operator form of the function that deciphers with a shift of 5:

 In:= Out= Use the operator:

 In:= Out= ### Applications (2)

Decipher a message:

 In:= Out= Decipher a message:

 In:= Out= ### Properties and Relations (2)

Enciphering can be done using the deciphering function but with a negative shift:

 In:= Out= If the shift is an integer multiple of 26, the Caesar decipher does not affect the input string:

 In:= Out= ### Neat Examples (1)

Try out all 25 options to decipher a message and find the original message:

 In:= Out= SHuisman

## Version History

• 1.0.1 – 31 August 2021
• 1.0.0 – 14 June 2019