What are the major code breaks in the history of cryptography? Which code breaks changed the face of a battle or another major event? Which one had nationwide consequences?
Besides the ones mentioned in the already existing Q&A "Examples of modern, widely used ciphers that suddenly fell?", the following major code breaks have been notable in history:
- The break of the German Enigma based codes in the second world war by the team led by Alan Turing;
- Project Magic / Purple;
- Crypto AG's Hagelin C(X)-52, which can be regarded as a break from an operational standpoint;
- The Zimmermann Telegram;
- Break of Lorenz cipher;
- Halske T52;
- Project Venona;
- Break of JN-25.
The case of the Queen Mary of Scots is interesting. She paid with her head the cost of using a weak cipher (breakable with frequency analysis). But that happened many centuries ago so ciphers using complicated substitution were the best option at the time.
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