One-time pad (XOR)
True one-time-pad XOR: a key at least as long as the message, used once, mathematically unbreakable if kept secret and never reused. Refuses a key that is too short instead of silently repeating it.
One-time pad (XOR) XORs your message against a key no shorter than it, byte for byte, turning away anything shorter rather than stretching it to fit. Encrypt prints hex; decrypt tries UTF-8 first and falls back to hex on failure. It is unbreakable only when the key stays truly random and used exactly once, a guarantee this tool cannot check.
Questions
What key length does it require?
At least as many bytes as the message or ciphertext. A shorter key is refused, naming both lengths, rather than being reused or repeated.
What format is the key?
Even-length hex, if it parses as hex, otherwise the typed text itself as UTF-8 bytes.
What does decrypt mode show?
It tries to read the XOR result as UTF-8 text first, and falls back to printing hex if that fails.
Is this unbreakable?
Only if the key is truly random, kept secret, and never reused, the classic one-time-pad conditions. The tool has no way to check any of those three.
Can I use this from the command line?
Yes, it runs the same on the page, the CLI and MCP.