For some time it had been apparent that the DES, though never broken in the usual cryptanalytic sense, was no longer secure.
Another famous example of cryptanalytic success was the deciphering by the British during World War I of a telegram from the German foreign minister, Arthur Zimmermann, to the German minister in Mexico City, Heinrich von Eckardt, laying out a plan to reward Mexico for entering the war as an ally of Germany.
Obviously, there is no counterpart to this kind of cryptanalytic attack in single-key systems.
It adds: "The Israeli side enjoys the benefits of expanded geographic access to world-class NSA cryptanalytic and SIGINT engineering expertise, and also gains controlled access to advanced US technology and equipment via accommodation buys and foreign military sales".
Vernam suggested a means of introducing equivocation at the same rate at which it was reduced by redundancy among symbols of the message, thereby safeguarding communications against cryptanalytic attack.
In other words, the system is unconditionally secure, not because of any failure on the part of the cryptanalyst to find the right cryptanalytic technique but rather because he is faced with an irresolvable number of choices for the key or plaintext message.
The advantage of these electronic machines was speed of operation; the disadvantages were the cryptanalytic weaknesses inherited from mechanical rotor machines and the principle of cyclically shifting simple substitutions for realizing more complex product substitutions.
"In the future, superpowers will be made or broken based on the strength of their cryptanalytic programs," a 2007 document said.
"Cryptanalytic capabilities are now coming online.
"While the specifics of how our intelligence agencies carry out this cryptanalytic mission have been kept secret, the fact that NSA's mission includes deciphering enciphered communications is not a secret, and is not news.
