TheCodeBreakers
letter cryptogram, but dozens for those of two letters, and zillions for
those of 100.
A final hope flickers. Suppose that the cryptanalyst obtains the
plaintext of a given cryptogram, perhaps through theft or the error of a
radio operator. Can he use the key that he can recover to determine the
system on which that key was built, and so predict future keys? No,
because a random key has no underlying system—if it did, it would not
be random.
These are empiric proofs. It is possible, however, to demonstrate a
priori that the one-time system is unbreakable. This constitutes the proof
that it is theoretically unbreakable.
In essence, the Vernam encipherment constitutes an addition—an
addition based on the Baudot alphabet, but an addition nonetheless.
Suppose then that the plaintext is 4 and the key is 5. The ciphertext will
be 9. Now, given only this, the cryptanalyst has no way of knowing
annaabi.ee 
