Abstract :
Histories of cryptography are apt to be episodic. For long periods of time nothing seems to be happening–but for good reasons. Cryptographic offices do not announce successful penetration of another nation´s secrecy system. On the contrary, they guard this information so jealously that they hesitate even to use any intelligence gained through it, lest the other nation, realizing the discovery, should discontinue its use of the now transparent system.
