Mechanising Cryptography

Professor Richard Walton CB

Cryptography is concerned with the application of technology to the problem of encrypting and decrypting a message.

The Mathematics is subordinate to the technology

20th Century Cryptography Development of Crypt in the 1900s Manual Methods

– Slow– Laborious– Error-Prone

Need to mechanise Importance of technology for design Nature of technological constraints

CRYPTOGRAPHYSecurity

Usability Cost

Cryptanalysis 1918 Knowledge of language Frequency Analysis Key Re-use (Depth)

Skill Requirement:To solve crossword puzzles

in foreign languages

Rotor Machines

Rotors

Commercial Enigma

Enigma

Enigma

Army

Navy

Navy – 4 wheel

Early Machine Cryptography Limitations of Security Design Balance Security against Cost Usability – Human Factors

Electronics – 1960-1980 Shift Registers and Simple Logic Gates Linear Algebra Galois Theory Rich Mathematical structure Rigorous Analysis Expensive Components

Large Scale Integration Application Specific Integrated Circuits Complex Algorithms Tailored to purpose Standard Cryptographic Primitives Software and Firmware

Public Key Cryptography Key Management Non-Secret Encryption

– Ellis, Cocks & Williamson– Beyond 1970’s technology

Widespread after 1985 Search for easier solutions

– Elliptic Curve Cryptography

Next Challenge

Quantum Computers destroycurrent Public Key algorithms

Find new algorithms to resist Quantum Computer attacks

Mechanising CryptographyAcknowledgement

Illustrations concerning Enigma in this presentation have been taken from the user manual for Enigma – E

by Paul Reuvers & Marc Simons.

For details of Enigma-E, which is available for purchase from Bletchley Park Museum, see www.xat.nl/enigma-e/