Notes:
1500 BC Intaglio: pictographic embossed stone stamp merchants mark to uniquely identify goods. Kind of ancient digital Signature.
1466 Cipher Disk later known as captain midnights cipher disk, not broken until 1800's
1790 Jefferson George Washington's secretary of state. Cylindrical wooden alphabet, message spelt out then alternate line written down. Later version adapted by US military and used between 1922 and WWII.
1933-1945 Enigma: Initially Broken by Polish Marian Rejewski further breaks were made by the likes of Alan Turing at Bletchley Park in the UK. Also home to the first programmable computer Colussus.
1976 DES: Still used today as a component in triple DES algorithm. 1976 also see's the introduction of the concept of public key encryption.
1991 (PGP): Phil's Response to NSA plan to hold back-door key to all US encryption systems. (Senate Bill 266, a 1991, Clipper Chip) manufacturers of secure communications equipment to insert special "trap doors"