A1Z26 cipher is a simple direct substitution cipher. It goes with other name like (letters to Numbers, Numbers to letters, and Letter-Number code).

It’s the simplest possible letters to numbers translation cipher.

Basically, A1Z26 cipher encrypts by replacing each letter by its position in the alphabet. For example, letter A with the digit 1, letter B with the digit 2 and so on.

A1Z26 simply replaces each letter of the alphabet by its number in the alphabet. Most of the time all letters are set to lowercase and English alphabet is used.

All non-alphabet symbols are not changed, for example, dashes and spaces.

A1Z26, or variants of letters to numbers, is frequently used in geocaching mystery caches (puzzle caches), CTFs and logic puzzles.

## How to encrypt using Letter-to-Number cipher

A1Z26 encryption requires to count the positions or ranks of letters in the alphabet. If it’s the Latin alphabet of 26 characters here is the correspondence table.

Letters to numbers conversion table.

 Letter in alphabet Number or Rank in alphabet A 1 B 2 C 3 D 4 E 5 F 6 G 7 H 8 I 9 J 10 K 11 L 12 M 13 N 14 O 15 P 16 Q 17 R 18 S 19 T 20 U 21 V 22 W 23 X 24 Y 25 Z 26

To encrypt a message, replace each letter with its position in the alphabet (A = 1, B = 2, … Z = 26).

For example, lets encrypt the message “Attack at noon”.

By looking up in the letters to numbers conversion table, letter A corresponds to 1, letter T corresponds to 20 and so on.

Thus, the message “Attack at noon” is encrypted as “1 20 20 1 3 11 1 20 14 15 15 14”.

## How to decrypt Number-to-Letter cipher

Decryption requires taking each number and replace it with the letter of same position in the alphabet: 1 = A, 2 = B, … 26 = Z.

For example, lets decrypt the ciphertext: 11 9 6 1 14 7 1.

By replacing each number to correspond letter of the alphabet depending on its rank, the ciphertext (11 9 6 1 14 7 1) is decrypted to (kifanga).

Use the above A1Z26 cipher decoder and encoder to translate numbers to letters or letters to numbers.

## How to recognize Letter-to-Number ciphertext

The encrypted message is made of numbers between 1 and 26, sometimes the number 0 is used to encode a space.

The digit 5 for E is supposed to appear frequently for an English text. This encryption is sometimes called alphanumeric code.

## What are the variants of the Letter-to-Number cipher?

1. Shift of numbers: the alphabet can start with A = 0 or A = 1, but also A = 65 or A = 97 (ASCII code).

2. Use of supplementary character for space (usually 0 or 27).

3. Use of leading zeros to be able to concatenate numbers AB = 0102, else AB = 12 and 12 = L.

4. Use of a custom alphabet, or reversed alphabet (A = 26, Z = 1).

5. Use of modulo 26 in order to get 1 = A, 2 = B, … 26 = Z then 27 = A, 28 = B and so on.

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