In short, the Navy, specifically U boats, used a non-standard, stronger crypto (in this, more rotors) Enigma machine, called M4. They formed their own Enigma network called "Triton" which the allies called "Shark".
Due to their hardening, and less message sent for traffic analysis, these machines were "safer" against cryptanalysis.
In short, the Navy, specifically U boats, used a non-standard, stronger crypto (in this, more rotors) Enigma machine, called M4. They formed their own Enigma network called "Triton" which the allies called "Shark".
Due to their hardening, and less message sent for traffic analysis, these machines were "safer" against cryptanalysis.