[kiwijimm]

The thing the allies did know and the Germans largely ignored was the fact that their Ciphers could be vulnerable. They tested them. Despite some pockets of dissent the Germans thought enigma was totally secure and never subjected it to proper analysis from their side. Also the German hierarchy during the war made it difficult for dissenting voices from the ranks to be heard on these topics.

Donitz was one exception. He suspected the allies were breaking enigma and hence the security of the naval enigma's was increased. I believe he advocated for more changes but was stopped or ran out of time.

After the war the allies sent in teams of intelligence operatives to assess how much the Germans knew about allied codebreaking and intelligence efforts. What they found was that the secrecy of Ultra worked and held throughout the war.

James