The British had been cracking Soviet codes for years, but in 1927 everything was stopped due to an incredible political blunder: the British government decided to release some intercepts to justify breaking off relations with the USSR. Naturally, the Soviets changed the codes, and for several years the British were left in the dark. This mistake would not be repeated again during World War II or the Cold War. The event, called the “SigInt Catastrophe of 1927” (Signal Intelligence), led the Soviets to adopt the (theoretically) uncrackable “one-time pad,” which uses random additives used only once. If used correctly, the system is unbreakable. But the Soviets will make mistakes, such as using the same additive multiple times, which will lead to the decryption of some messages.
