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.
Download slides for PowerPoint or slides as PDF (because of animations some slides aren't clear).
An article on this topic, "Ciphers through the ages" by Peter Rowlett, appears in issue 10 of iSquared Magazine (Winter 2009/10), on pages 24-27. Download issue 10 of iSquared Magazine for free.
Download companion audio podcast episode to this talk & article, which extends the topic by covering cracking the Vigenere cipher, from the Travels in a Mathematical World podcast.