"The earliest known use of cryptography goes back to Ancient Egypt, where scribes used hieroglyphs in a non-standard fashion on monuments. This was not considered however as a serious attempt to hide information."
"The Greeks encrypted their messages wrapping a tape around a stick (the scytale), rendering the message unreadable when unwound. The receiver had to use a stick of the same diameter to recover the information."
"Steganography was the method employed to hide a message rather than encrypting it. Herodotus mentions its use when Persia communicates with Greece tattooing a message on a shaved head, concealing it as hair grew back."
"The Caesar cipher is one of the simplest and most known encryption technique, substituting each letter of the message by another letter down a fixed number in the alphabet. It was named after Julius Caesar, who used it in his private correspondence."
"The Arabs, with mathematician Al-Kindi, developed techniques to break monoalphabetic ciphers through frequency analisis – noting that certain letters are more frequent than others in languages (like E in English)."
"As cryptanalysis progressed, more sophisticated encryption methods were needed. Leon Battista Alberti, the “father of Western Cryptology”, developed polyalphabetic ciphers, using different ciphers every few words."
"A form of polyalphabetic substitution, the Vignère cipher encrypts texts using a series of interwoven Caesar ciphers, based on the letters of a keyword. While Giovan Battista Bellaso invented the method, Blaise de Vigenère perfected it through a stronger autokey cipher."
"In England, the Babington plot, which aimed at the assassination of Queen Elizabeth I, was uncovered by cryptanalysis, leading to the implication and execution of Mary, Queen of Scots."
"The work of mathematician Charles Babbage helped Britain during the Crimean War, by breaking polyalphabetic ciphers."
"During WWI, Germany sent a telegram to Mexico, offering to join the war. This was intercepted and decoded by British intelligence, who had to ruse to reveal it to the US without disclosing they had broken the German codes."
"Invented by German engineer Arthur Scherbius, Enigma was a cipher machine to encrypt commercial, diplomatic and military communication. Thought to be unbreakable, it was heavily used by Germans during WWII, only to be defeated by efforts led by mathematicians in Bletchley Park."
"The US army used the Navajo’s own language to code war messages, which was instrumental in winning against the Japanese during WWII. While this was not strictly speaking cryptography, the code was never broken – a remarkable fact in military history."
"To s ecure electronic communications in financial organisations, the US establish the Dat Encryption Standard (DES), a data encryption algorithm."
"Transmitting keys to decode has always been a challenge in cryptography, but Diffie and Hellman solved for that when introducing a new key distribution system, using asymmetric encryption through private keys (for decryption) and public keys (for encryption)."
"Invented by Phil Zimmerman, Pretty Good Privacy (PGP) is an encryption program to provide privacy and authenticat ion for data communications. As the system was released, it received a lot of government criticism."