# Implementing Atbash Cipher

• Difficulty Level : Easy
• Last Updated : 21 Mar, 2023

Definition: Atbash cipher is a substitution cipher with just one specific key where all the letters are reversed that is A to Z and Z to A. It was originally used to encode the Hebrew alphabets but it can be modified to encode any alphabet.

Relationship to Affine: Atbash cipher can be thought of as a special case of Affine cipher with both the keys being 25, i.e, a = 25 & b = 25

Atbash Key

Algorithm: The following key is used in the Atbash algorithm

ABCDEFGHIJKLMNOPQRSTUVWXYZ
ZYXWVUTSRQPONMLKJIHGFEDCBA

Encryption

To encipher a message, find the letter you wish to encipher in the top row, then replace it with the letter in the bottom row. In the example below, we encipher the message ‘GEEKS FOR GEEKS’. The first letter we wish to encipher is ‘G’, which is above ‘T’, so the first ciphertext letter is ‘T’. The next letter is ‘E’, which is above ‘V’, so that comes next. The whole message is enciphered as:

GEEKS FOR GEEKS
TVVPH ULI TVVPH

Decryption

Similarly if we want to decrypt say ‘TVVPH ULI TVVPH’ we would replace the first letter ‘T’ with ‘G’. The second letter ‘V’ with ‘E’ and so forth substituting all letters including the last one ‘H’ with ‘S’. The deciphered message will be :

TVVPH ULI TVVPH
GEEKS FOR GEEKS

The Approach: Here, mapping of every element is done for the key as ‘key-value’ pairs in a dictionary and then it is used as a lookup table whenever you want to encrypt a single character. Code:

Implementation:

## C++

 // C++ program to implement Atbash Cipher #includeusing namespace std; // Map to lookup various alphabetsmap lookup_table = {{'A', 'Z'}, {'B', 'Y'}, {'C', 'X'}, {'D', 'W'}, {'E', 'V'}, {'F', 'U'},                                {'G', 'T'}, {'H', 'S'}, {'I', 'R'}, {'J', 'Q'}, {'K', 'P'}, {'L', 'O'},                                {'M', 'N'}, {'N', 'M'}, {'O', 'L'}, {'P', 'K'}, {'Q', 'J'}, {'R', 'I'},                                {'S', 'H'}, {'T', 'G'}, {'U', 'F'}, {'V', 'E'}, {'W', 'D'}, {'X', 'C'},                                {'Y', 'B'}, {'Z', 'A'}}; // Function to implement Atbash Cipherstring atbash(string message){    string cipher = "";    for(char letter : message)    {        // Checking for space        if(letter != ' ')        {            // Adds the corresponding letter from the lookup_table            cipher += lookup_table[toupper(letter)];        }        else        {            // Adds space            cipher += ' ';        }    }    return cipher;} // Driver function to run the programint main(){    // Encrypt the given message    string message = "GEEKS FOR GEEKS";    cout << atbash(message) << "\n";     // Decrypt the given message    message = "TVVPH ULI TVVPH";    cout << atbash(message) << "\n";     return 0;} // This code is contrbuted by prince

## Java

 // Java program to implement Atbash Cipher import java.util.HashMap; public class Main {    // Map to lookup various alphabets    static HashMap lookup_table = new HashMap(){{        put('A', 'Z'); put('B', 'Y'); put('C', 'X'); put('D', 'W'); put('E', 'V'); put('F', 'U');        put('G', 'T'); put('H', 'S'); put('I', 'R'); put('J', 'Q'); put('K', 'P'); put('L', 'O');        put('M', 'N'); put('N', 'M'); put('O', 'L'); put('P', 'K'); put('Q', 'J'); put('R', 'I');        put('S', 'H'); put('T', 'G'); put('U', 'F'); put('V', 'E'); put('W', 'D'); put('X', 'C');        put('Y', 'B'); put('Z', 'A');    }};     // Function to implement Atbash Cipher    public static String atbash(String message)    {        String cipher = "";        for(char letter : message.toCharArray())        {            // Checking for space            if(letter != ' ')            {                // Adds the corresponding letter from the lookup_table                cipher += Character.toLowerCase(lookup_table.get(Character.toUpperCase(letter)));            }            else            {                // Adds space                cipher += ' ';            }        }        return cipher;    }     // Driver function to run the program    public static void main(String[] args)    {        // Encrypt the given message        String message = "GEEKS FOR GEEKS";        System.out.println(atbash(message));         // Decrypt the given message        message = "TVVPH ULI TVVPH";        System.out.println(atbash(message));    }} // Contributed by adityasharmadev01

## Python

 # Python program to implement Atbash Cipher # This script uses dictionaries to lookup various alphabetslookup_table = {'A' : 'Z', 'B' : 'Y', 'C' : 'X', 'D' : 'W', 'E' : 'V',        'F' : 'U', 'G' : 'T', 'H' : 'S', 'I' : 'R', 'J' : 'Q',        'K' : 'P', 'L' : 'O', 'M' : 'N', 'N' : 'M', 'O' : 'L',        'P' : 'K', 'Q' : 'J', 'R' : 'I', 'S' : 'H', 'T' : 'G',        'U' : 'F', 'V' : 'E', 'W' : 'D', 'X' : 'C', 'Y' : 'B', 'Z' : 'A'} def atbash(message):    cipher = ''    for letter in message:        # checks for space        if(letter != ' '):            #adds the corresponding letter from the lookup_table            cipher += lookup_table[letter]        else:            # adds space            cipher += ' '     return cipher # Driver function to run the programdef main():    #encrypt the given message    message = 'GEEKS FOR GEEKS'    print(atbash(message.upper()))         #decrypt the given message    message = 'TVVPH ULI TVVPH'    print(atbash(message.upper()))  # Executes the main functionif __name__ == '__main__':    main()

## Javascript

 // Javascript program to implement Atbash Cipher // This script uses objects to lookup various alphabetslet lookup_table = {'A': 'Z', 'B': 'Y', 'C': 'X', 'D': 'W', 'E': 'V','F': 'U', 'G': 'T', 'H': 'S', 'I': 'R', 'J': 'Q','K': 'P', 'L': 'O', 'M': 'N', 'N': 'M', 'O': 'L','P': 'K', 'Q': 'J', 'R': 'I', 'S': 'H', 'T': 'G','U': 'F', 'V': 'E', 'W': 'D', 'X': 'C', 'Y': 'B', 'Z': 'A'}; function atbash(message) {  let cipher = '';  for (let letter of message) {    // checks for space    if (letter !== ' ') {      // adds the corresponding letter from the lookup_table      cipher += lookup_table[letter];    } else {        // adds space        cipher += ' ';    }  }  return cipher;} // Driver function to run the programfunction main() {  // encrypt the given message  let message = 'GEEKS FOR GEEKS';  console.log(atbash(message.toUpperCase()));   // decrypt the given message  message = 'TVVPH ULI TVVPH';  console.log(atbash(message.toUpperCase()));} // Executes the main functionmain();   // This code is contribued by adityashatmfh

Output

TVVPH ULI TVVPH
GEEKS FOR GEEKS

Advantages : Since its just an affine cipher with both a = 25 = b we don’t need to write separate functions for encryption and decryption. We can re-use the same function for both purposes.

Analysis : It has one constant key it is the easiest cipher to break and provides almost no security. Anyone can assume that it is atbash and decrypt the message by reversing the letters.

This article is contributed by Palash Nigam . If you like GeeksforGeeks and would like to contribute, you can also write an article using write.geeksforgeeks.org or mail your article to review-team@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.

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