Public Key Cryptography - Computerphile (6:19)

Spies used to meet in the park to exchange code words, now things have moved on - Robert Miles explains the principle of Public/Private Key Cryptography

note1: Yes, it should have been 'Obi Wan' not 'Obi One' :) note2: The string of 'garbage' text in the two examples should have been different to illustrate more clearly that there are two different systems in use.