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Substitution ciphers: Ancient - Renaissance

University of Nottingham (01/12/2009).

Cryptography is the process by which messages are communicated through secret means. Cipher cryptography converts messages by applying some cipher algorithm with a secret key to a plaintext message, converting it into a ciphertext message that cannot be read by interceptors. Cryptanalysis is the science that attempts to decipher these messages without access to the secret key.

This talk will focus on substitution ciphers and demonstrate the processes of encrypting and breaking some examples of these. The focus is on the battle between cryptographers - who create cipher systems - and cryptanalysts - who attempt to break them. As cryptanalysis develops more ingenious ciphers must be created and this constant struggle evolves from Roman generals, through the Golden Age of Islam to political intrigue in Renaissance Europe.

This talk will provide a gentle introduction and will assume no prior knowledge of cryptography.

This talk was recorded for the web as part of the History of Maths and x series.

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