1355-1418 - Ahmad al-Qalqashandi writes Subh al-a 'sha, a 14-volume encyclopedia including a section on cryptology, attributed to Ibn al-Durayhim (1312–1361). The list of ciphers in this work include both substitution and transposition, and for the first time, a cipher with multiple substitutions for each plaintext letter. It also included an exposition on and worked example of cryptanalysis, including the use of tables of letter frequencies and sets of letters which cannot occur together in one word.
1450 - The Chinese develop wooden block movable type printing.
1450-1520 - The Voynich manuscript, an example of a possibly encoded illustrated book, is written.
c. 1854 - Babbage's method for breaking polyalphabetic ciphers (pub 1863 by Kasiski)
1855 - For the English side in Crimean War, Charles Babbage broke Vigenère's autokey cipher (the 'unbreakable cipher' of the time) as well as the much weaker cipher that is called Vigenère cipher today. Due to secrecy it was also discovered and attributed somewhat later to the Prussian Friedrich Kasiski.
June 1942 - Battle of Midway where U.S. partial break into Dec 41 edition of JN-25 leads to turning-point victory over Japan
April 1943 - Admiral Yamamoto, architect of Pearl Harbor attack, is assassinated by U.S. forces who know his itinerary from decoded messages
April 1943 - Max Newman, Wynn-Williams, and their team (including Alan Turing) at the secret Government Code and Cypher School ('Station X'), Bletchley Park, Bletchley, England, complete the "Heath Robinson". This is a specialized machine for cipher-breaking, not a general-purpose calculator or computer.
December 1943 - The Colossus computer was built, by Thomas Flowers at The Post Office Research Laboratories in London, to crack the German Lorenz cipher (SZ42). Colossus was used at Bletchley Park during World War II - as a successor to April's 'Robinson's. Although 10 were eventually built, unfortunately they were destroyed immediately after they had finished their work - it was so advanced that there was to be no possibility of its design falling into the wrong hands.
1944 - Patent application filed on SIGABA code machine used by U.S. in World War II. Kept secret, it finally issues in 2001
1946 - The Venona project's first break into Soviet espionage traffic from the early 1940s
1985 - Walker spy ring uncovered. Remaining KL-7's withdrawn from service.
1986 - After an increasing number of break-ins to government and corporate computers, United States Congress passes the Computer Fraud and Abuse Act, which makes it a crime to break into computer systems. The law, however, does not cover juveniles.
1994 - Peter Shor devises an algorithm which lets quantum computers determine the factorization of large integers quickly. This is the first interesting problem for which quantum computers promise a significant speed-up, and it therefore generates a lot of interest in quantum computers.
1994 - Russian crackers siphon $10 million from Citibank and transfer the money to bank accounts around the world. Vladimir Levin, the 30-year-old ringleader, uses his work laptop after hours to transfer the funds to accounts in Finland and Israel. Levin stands trial in the United States and is sentenced to three years in prison. Authorities recover all but $400,000 of the stolen money.
1994 - Formerly proprietary, but un-patented, RC4 cipher algorithm is published on the Internet.
1997 - Ciphersaber, an encryption system based on RC4 that is simple enough to be reconstructed from memory, is published on Usenet.
October 1998 - Digital Millennium Copyright Act (DMCA) becomes law in U.S., criminalizing production and dissemination of technology that can circumvent technical measures taken to protect copyright.
October 1999 - DeCSS, a computer program capable of decrypting content on a DVD, is published on the Internet.
2000 and beyond
January 14, 2000 - U.S. Government announce restrictions on export of cryptography are relaxed (although not removed). This allows many US companies to stop the long running process of having to create US and international copies of their software.
September 6, 2000 - RSA Security Inc. released their RSA algorithm into the public domain, a few days in advance of their U.S. Patent 4,405,829 expiring. Following the relaxation of the U.S. government export restrictions, this removed one of the last barriers to the worldwide distribution of much software based on cryptographic systems