Letter Number Cipher (A1Z26)
The Letter Number Cipher (also known as A1Z26 Cipher) is one of the simplest substitution ciphers. The idea is straightforward — every letter in the alphabet is replaced by its position number. A becomes 1, B becomes 2, and so on, all the way to Z, which becomes 26.
Encoding
To encode a message, simply replace each letter with its alphabetical position number. A separator (like a dash -) is used between numbers so they can be unambiguously read back.
- H → position 8 →
8 - E → position 5 →
5 - L → position 12 →
12 - O → position 15 →
15 - W → position 23 →
23
So "HELLO WORLD" turns into a sequence of numbers separated by dashes — easy to write down, but not immediately obvious to someone who doesn't know the trick!
Decoding
To decode, just do the reverse — take each number and find the letter at that position in the alphabet:
- Split the encoded message by the separator (
-) - Convert each number back to its corresponding letter (1 = A, 2 = B, …, 26 = Z)
- Concatenate the letters to get the original message
Spaces in the original message are typically encoded as 0 or preserved as a space between groups of numbers.
Example
Input: HELLO WORLD
Encoded: 8-5-12-12-15---23-15-18-12-4
Decoded: hello world
The decoder reads 8 as the 8th letter of the alphabet (H), 5 as the 5th letter (E), 12 as the 12th letter (L), and so on — reconstructing the original message step by step!