Bulldozer: A Cribless Rapid Analytical Machine (RAM) Solution to Enigma and its Variations

Abstract

The breaking of German Naval Enigma ciphers relied heavily on finding cribs. Most of the now well-known bombes and Rapid Analytical Machine(s) were designed to assist with discovering cribs. What if the Germans make changes in their Enigma machine, for which there were few or no cribs? This article looks at a time when this nearly happened and Bulldozer, a machine designed to break keys without cribs.

Keywords:

• Barnacles
• bulldozer
• crib
• dolphin
• EINS catalog
• fillibuster
• German Naval Enigma
• Grundstellung (Grund)
• hypo
• offizier
• plaice
• Rapid Analytical Machine(s)
• shark

Acknowledgements

The author wishes to thank Colin Burke for suggesting this topic and for sharing his material, comments, and encouragement. I also wish to thank Keith Batey, former Bletchley Park cryptanalyst, for reading and commenting on a draft of this article. Without them, this article would not have been written.

Notes

¹Radiogram from W. F. Friedman to MILID, 22 May 1943, in American Embassy, London Messages to Military Intelligence Division. National Archives, College Park (NACP). RG 457, Records of the National Security Agency/Central Security Service (NSA), Historic Cryptographic Collection (HCC), Box 1026. Hereinafter referred to as NACP, NSA, and HCC.

²Memorandum from John N. Seaman to C. O. Arlington Hall Station, Va.; RAM File, 1944. RG 457, NACP, NSA, HCC Box 1033.

³Memorandum from S. P. Collins, Signal Corps, to Signal Officer, Headquarters, ETOUSA; RAM File, 1944. RG 457, NACP, NSA, HCC, Box 1033.

⁴ C. H. O'D Alexander History of Enigma. June 1943. UK: National Archives. A copy of this manuscript, original at the National Archives (UK), was made available to me be Ralph Erskine.

⁵5750/176 CNSG-OP-20GM-G/GM-1-C-3/GM-11GE-1/GY-A-1 Daily War Diary (1 of 5); RG 38; Records of the Office of the Chief of Naval Operations; Records of the Naval Security Group Central Depository, Crane, Indiana; CNSG Library; Box 113. For fuller description of T Machine, see Enigma (Conferences, Theory, Related Information) Bombe; NR 1737; RG 457; NSA HCC; Box 705.

⁶Conference II—Enigma Theory. 27 March 1934. NR 1737, R6 457; NSA; HCC; Box 705.