In cryptography, encoding or encrypting a message means to use some kind of symbols to represent the letters in a message. Decoding or decrypting a message puts the secret message back into a readable form. Secret codes have been around for as long as there has been written language. As a matter of fact, the English language could be considered a code that encrypts thoughts and statements that your brain decodes using those complex grammatical structures taught to your by your underappreciated English teachers. Computers routinely use codes; all these letters and numbers that you see on your computer screen are simply the decoded messages produced from a series of ones and zeros called binary code.

In this project, you will learn to use invertible matrices to encode and decode a secret message.

Encryption and HUGE numbers

This Numberphile video explains RSA encryption, which is the type of encryption used by modern digital devices. The bit in here about writing down the remainder is in called modular arithmetic. Duration_9_21

158,962,555,217,826,360,000 (Enigma Machine)

In this Numberphile video, James Grime discusses the cryptography employed by the Germans during WWII, whose encrypted their secret correspondence using an Enigma Machine. Duration_11_51

Flaw in the Enigma Code

In a continuation of the previous video, Dr. Grime discusses the flaw in the Enigma Machine, that any given letter would never encode as itself. Alan Turing built the first computer to exploit this flaw and break the Enigma Code. Duration_10_58

Not a Robot, But a Ghost

Taken from his 2009 album Noble Beast, Andrew Bird alludes to cracking codes and winning wars. One could interpret this as describing the tragic life of Alan Turing. Or perhaps the song concerns decrypting the unspoken codes exchanged between participants in a difficult relationship. I'm not sure. Ask your English teacher. Duration_5_37