One-Time Pad XOR Tool

About this calculator

The one-time pad, formalized by Gilbert Vernam, achieves theoretically perfect secrecy by combining each plaintext byte with a key byte of equal length using XOR — a reversible bitwise operation where applying the same key twice returns the original data (P ⊕ K = C, then C ⊕ K = P). Perfect secrecy only holds if the key is truly random, exactly as long as the message, and never reused; in practice, the same math with a short repeating key (as this tool does) produces a simple, breakable stream cipher rather than a true unbreakable pad.

This tool XORs a message against a key — repeating the key to match the message length — to encrypt text into hex or decrypt hex back into text. Cryptography students use it to see XOR-based encryption mechanics firsthand, and CTF players and security learners use it to quickly encode or decode XOR-cipher challenges by hand.