[Stolpe]

"The story of the seizure of the machine by Balme and his shipmates was kept secret until the mid-1970s". I've always been intrigued by this fact. Does anyone know why this was kept a secret for so long?

[ptha]

Interestingly from: https://en.wikipedia.org/wiki/Enigma_machine#History

"An estimated 100,000 Enigma machines were constructed. After the end of World War II, the Allies sold captured Enigma machines, still widely considered secure, to developing countries".

I'm sure they were quite happy to sell Enigma and also decrypt their communications for nearly another 30 years.

[arethuza]

Another interesting thing to note is that the Soviets knew fine well that the UK could decrypt German codes from their spies at Bletchley Park.

[anovikov]

If the Enigma machines were operated properly, they could never be broken. Breaking them were a result of German lack of discipline and irresponsibility, not machine's weakness (maybe a simple inscription on the cover of machine in the bold letters would help though, machine designers just expected too much from their enlisted, barely literate operators).

[bendykstra]

Just as during WWII, during WWI, the British had a very sophisticated interception and decryption program[1]. Its capabilities were also kept secret for long after the war and the Germans remained largely ignorant of how thoroughly their codes had been broken. I think if the work during WWI had been revealed earlier, the Germans would have been more careful and would have avoided repeating some of the mistakes of WWI. It was shown to be a wise policy after WWI, so I'm not surprised that they continued it after WWII, especially with the start of the Cold War.

1. https://en.wikipedia.org/wiki/Room_40

[danielam]

I can't speak about the relative sophistication of British cryptanalysis during WWI, but Bletchley owed much of its sophistication to the Poles. The Polish Cipher Bureau was responsible for bringing mathematical and computational techniques into cryptanalysis while the French and the British were still largely employing linguistic analysis. Few realize that the Enigma was actually broken and reverse engineered by the Cipher Bureau before two new rotors were added by the Germans less than a year before the War, or that Turing's bombe was developed from Rejewski's bomba.

[bboreham]

Many countries used Enigma and its derivatives after the war; the UK and US did not want those countries to know they could read their messages.

[conjectures]

This is true.

[pjc50]

That sounds like the 30 year rule in action. At the time it was done, it would have been extremely secret, and secrecy was not abandoned simply because the war was over.

Bletchley was kept secret for even longer.

[DanBC]

England keeps secrets for a long time. GCHQ have only just recently released stuff that Turing wrote.

[cromulent]

Yeah, they developed the equivalent of RSA in 1973 but only declassified it in 1997 so no-one knew about it and the RSA patent held.