XOR Cipher & XOR Calculator

Exclusive-or (XOR) is the building block of stream ciphers and one-time pads, and a favourite of malware authors and capture-the-flag puzzles. This tool XORs text, hex or Base64 data with a key that repeats as needed, XORs two equal-length hex strings, or tries all 256 single-byte keys and ranks the results by how English they look. Output comes as hex, Base64 and readable text.

How to use this tool

1. Choose a mode: XOR with a key, XOR two hex strings, or brute-force a single-byte key.
2. Paste the data and say whether it is text, hex or Base64.
3. Enter the key as hex, text or decimal byte values (not needed for brute force).
4. Copy the hex, Base64 or text result; XOR it again with the same key to undo it.

Formula

Cᵢ = Pᵢ ⊕ K(i mod k) and Pᵢ = Cᵢ ⊕ K(i mod k)

Pᵢ is byte i of the data and K the key of k bytes. Each output bit is 1 where the two input bits differ. Because x ⊕ k ⊕ k = x, encryption and decryption are the same operation. Brute force scores each of the 256 results with English letter frequencies plus a bonus for spaces.

Example

The text Hello (48 65 6c 6c 6f) XOR the single key byte 0x20 gives 68 45 4c 4c 4f — hELLO, because 0x20 is the bit that separates upper and lower case. The hex string 1c0111001f010100061a024b53535009181c XOR 686974207468652062756c6c277320657965 gives 746865206b696420646f6e277420706c6179, which reads "the kid don't play".