One Time Pad

• One Time Pad - A key for one use

• Encryption:

  • Message M (the ClearText), Key K
  • Encrypted Message C (CipherText) :
    C = M xor K
    

• Decryption :

  • CipherText C, Key K.
  • Decrypted Message (ClearText):
    M ? C xor K
    

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Notice that the key has to be in the length of the message.

C xor K = (M xor K) xor K = M xor 0 = M