AlanTuring.net

 

General Report on Tunny


 

This report describes the German Tunny encoding machine and tells the full story of how the British broke Tunny and decoded a steady stream of messages from Hitler and other members of the German High Command. It includes an account of Colossus, the world's first large-scale electronic digital computer, installed at Bletchley Park in December 1943.

The report was written at Bletchley Park in 1945 by three codebreakers, Jack Good, Donald Michie, and Geoffrey Timms.

This report was classified until the middle of 2000, when it was released to the Public Record Office, Kew (document reference HW 25/4 and HW 25/5).

The links in the table of contents below lead to a digital facsimile of the entire document.

The original document is Crown Copyright and is reproduced by permission of the Public Record Office.

photograph of Lorenz machine
 
photograph of Colossus
 
link to Tony Sale's retype of report

 

GENERAL REPORT ON TUNNY
With Emphasis on Statistical Methods

TABLE OF CONTENTS

Part 0

Preface

Part 1 INTRODUCTION

Contents
German Tunny
Cryptographic Aspects
Machines
Organisation
Some Historical Notes

Part 2 METHODS OF SOLUTION

Some Probability Techniques
Statistical Foundations
Machine Setting
Rectangling
Chi-breaking (from Cipher)
Wheel-breaking (from Key)
Cribs
Language Methods

Part 3 ORGANISATION

Mr Newman's Section
Major Tester's Section
Knockholt
Registration and Circulation
Tape-making and Checking
Chi-breaking and Cribs
Machine Setting
Wheel-breaking (from Key)
Language Methods

Part 4 EARLY METHODS AND HISTORY

The First Break
Early Hand Methods
Testery Methods 1942-4
Hand Statistical Methods

Part 5 MACHINES

General Introduction
Development of Robinson and Colossus
Colossus
Robinson
Specialised Counting Machines
Copying Machines
Simple Machines
Photographs

Part 6

Raw Materials and Production with Plans of Tunny Links

Part 7 REFERENCE

Glossary and Index
Notation
Bibliography
Chronology

Part 8

Conclusions

Part 9 APPENDICES

5202
Motor Rectangles
Thrasher
QEP Research
Mechanical Flags

Turing Archive Catalogue || Catalogue of Reference Articles || The Turing Archive Homepage

Site maintained by Jack Copeland and Gordon Aston.