# Primary sources

## Enigma mechanism

- **Anonymous (German Army manual).** *Schlüsselanleitung zur Chiffriermaschine Enigma I* (Berlin, 1930s). The official German operating manual. Public domain. Surviving copies in the National Archives, Kew.
- **Heeresnachrichtendienst documents** — captured rotor wirings (rotors I–V) are in the public domain. Standard cryptography textbooks reproduce them.
- **Tony Sale's website**, [codesandciphers.org.uk](https://codesandciphers.org.uk/). Sale led the rebuilds; the technical reconstruction notes are extensive and well-sourced.

## The Bombe

- **Alan Turing.** "Turing's Treatise on the Enigma" (the "Prof's Book", c.1940). Internal Bletchley document; declassified and digitised by GCHQ in 2012. The canonical description of the Bombe's logical operation.
- **Gordon Welchman.** *The Hut Six Story* (McGraw-Hill, 1982). Welchman invented the "diagonal board" that made the Bombe practical; his account is the best high-level reference.
- **Tony Sale.** *The Colossus Computer 1943–1996* (M&M Baldwin, 1998) — short companion volume with Bombe context.
- **John Harper / Bletchley Park Trust.** Technical reports on the working Bombe rebuild (completed 2006). Both the rebuild and the original blueprints are available at the National Museum of Computing.

## Historical context

- **Marian Rejewski, Jerzy Różycki, Henryk Zygalski.** Polish Cipher Bureau pre-1939 work. Rejewski's "bomba kryptologiczna" (1938) predates and inspires the British Bombe. Reports in *Annals of the History of Computing* and the Polish IPN archives.
- **Hugh Sebag-Montefiore.** *Enigma: The Battle for the Code* (Cassell, 2000). Cited.
- **B. Jack Copeland (ed.).** *Codebreakers: The Inside Story of Bletchley Park* (Oxford UP, 2010). Multi-author, primary-source-heavy.

## The Polish predecessor

The Polish *bomba kryptologiczna* (1938) and the British Bombe (1940) are technically distinct — Rejewski's bomba attacked the indicator-doubling weakness of pre-1940 German operating procedure; Turing's Bombe attacks the underlying rotor cryptography via cribs. The v0.6 lineage essay handles both. The British Bombe inherits its name from the Polish.

## What this sim will not claim

- **Diagonal board correctness in detail.** Welchman's diagonal board adds parallel deductions across the entire crib graph. Implementing it correctly is hard. v0.4 may implement a simplified version — the lineage essay will be explicit about what's modelled.
- **Speed.** The real Bombe rotated at about 1 revolution per second on the fast drum, completing a full search in ~15 minutes. Our visualisation runs slow-mo so the menu structure is readable.
- **Plugboard cycling.** The Bombe handles the plugboard implicitly via the "scrambler" wiring. We do the same.
- **Multi-Bombe coordination.** Bletchley ran ~200 Bombes; the operator scheduling and result combination is out of scope.