TheCodeBreakers
He can
no more pick the right solution from this list than he can from a
dictionary of military terms. The key does not help in limiting the
selection because, since it is random, any group of four letters is as
acceptable a keytext as
any other. The worst of it is that the possible solutions increase as the
message lengthens. There are only three possible solutions for a one-
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
annaabi.ee 
