One Time Pad Cipher

The One Time Pad (OTP) cipher is a substitution cipher that is impossible to crack (if used correctly).

To encrypt a message using OTP you combine each letter of your plaintext with a letter from your "pad". The pad is simply a large amount of text, some people use books as their pad, some people generate random letters.

To combine the letters you have to:

For example, let's use an alphabet of:


And let's encrypt this message, using this pad:


Going through every letter of the plaintext and pad gives us:



Complicated right? The calculator below can help. If you type a message into the plaintext box and a random pad into the pad box it will encrypt your message. If you instead provide a pad and a ciphertext it will decrypt for you.

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