One-Time Pad Generator

Generate a one-time pad

The one-time pad is the only cipher proven to be unbreakable, provided its key is truly random, as long as the message, kept completely secret, and never reused. This tool generates a random key, the pad, exactly as long as your letters-only message, and encrypts by adding each pad letter to the corresponding message letter modulo twenty-six. The result is a ciphertext that, without the pad, reveals nothing about the message because every possible plaintext is equally likely.

To decrypt, the recipient subtracts the same pad from the ciphertext, recovering the original message.

Why the rules matter

The one-time pad perfect secrecy depends entirely on following its rules. The key must be generated from genuine randomness, must be at least as long as the message, must be shared only between the two parties, and must be used once and then destroyed. Break any rule, especially reusing a pad, and the security collapses, which is exactly how historically real one-time-pad systems were broken.

This tool demonstrates the principle for learning and short messages, using the browser random generator where available. Distributing a truly secret pad to the recipient is the practical challenge that limits real-world use. All processing happens locally in your browser.

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