Venona Project - Decryption

Decryption

This message traffic, which was encrypted with a one-time pad system, was stored and analyzed in relative secrecy by hundreds of cryptanalysts over a 40-year period starting in the early 1940s. Due to a serious blunder on the part of the Soviets, some of this traffic was vulnerable to cryptanalysis. Somebody who was working for the manufacturers of Soviet secret-communication materials had reused pages of some of the one-time pads in other pads, which were then used for other secret messages. This defeated the purpose of the one-time pad, which provides perfect security when each page is used exactly once and then disposed of. It is unclear as to why this mistake was made, or by whom.