Details of Alan Turing’s Voice Encryption System

Really interesting piece of cryptographic history:

In November 2023, a large cache of his wartime papers—nicknamed the “Bayley papers”—was auctioned in London for almost half a million U.S. dollars. The previously unknown cache contains many sheets in Turing’s own handwriting, telling of his top-secret “Delilah” engineering project from 1943 to 1945. Delilah was Turing’s portable voice-encryption system, named after the biblical deceiver of men. There is also material written by Bayley, often in the form of notes he took while Turing was speaking. It is thanks to Bayley that the papers survived: He kept them until he died in 2020, 66 years after Turing passed away.

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Posted on July 17, 2026 at 7:02 AM • 3 Comments

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KC • July 17, 2026 10:07 AM

From the auction notes, Bayley recalls his first meeting with Turing:

‘He was a bit slapdash; I was very well-organised… This chap had his shirt hanging out. There were resistors and capacitors, as fast as he’d soldered one on another would fall off. It was a spider’s nest of stuff – a complete mess […] He was annoyed I mentioned his shirt hanging out. He took it for granted. He said I shouldn’t have mentioned it’ (Dermot Turing, Prof: Alan Turing Decoded, 2016, p.142)

Bayley later gave the papers to a family member with a note: “Some historical interest?“

Clive Robinson • July 17, 2026 10:57 AM

@ ALL,

Bayley is mentioned within the context of WWII era Hanslop Park.

What is only indirectly mentioned is Piccolo. As I’ve mentioned a couple of times over quite some time on This blog, it was designed by Bayley for the “Diplomatic Wireless Service”(DWS) out of Poundon, where he was an engineering senior.

It worked on the principle of lossless quenched resonators that are also covered by Turing’s Maths Notes. A paper on It’s design actually got published in the then world Famous “Wireless World” magazine in the 1960’s.

I was involved in a design of a cleaned up Piccolo in the 1980’s on a single Z80 8bit microprocessor.

For reasons I don’t know the UK Army Signals Establishment summary report on the testing of the resulting modem ended up being put up on the Internet by Google.

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