# Popular maths talks

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## Cryptography

University of Sheffield (19/11/2009).

Cryptography is the process by which messages are communicated through some secret means, often through a process on encrypting a message using some cipher process into an unintelligible sequence. This talk runs through 4 interesting cipher systems from history and demonstrates the processes of encrypting, decrypting and in some cases breaking these - Caesar cipher and frequency analysis, Vigenère cipher, Enigma and Public key cryptography. This talk will provide a gentle introduction and no previous knowledge of cryptography will be assumed. The talk features demonstrations using The Code Book on CD-ROM. Following the talk an activity can be operated whereby groups of students use The Code Book on CD-ROM's encryption and decryption tools to crack each others messages.