1. Introduction to Cryptography

History of cryptography – A timeline of important events

Cryptology is a very young science. Although humans have had rudimentary forms of cryptography for thousands of years, the systematic study of cryptology as a science only began about a hundred years ago. The advent of computers made cryptography many orders of magnitude more complex than it had been previously.

  • 1900 BC – First evidence of altered symbols in text found in the tomb of Khnumhotep II in Egypt. The writings weren’t meant to be secret, but are the first evidence we have of someone altering encoding symbols.
  • 100 BC – Ceasar Cipher. Julius Caesar was known to use a form of encryption to convey secret messages to his army generals posted on the war front. This substitution cipher, known as the Caesar cipher, is perhaps the most mentioned historic cipher (an algorithm used for encryption or decryption) in academic literature. It’s a simple cipher where each character of the plain text is simply substituted by another character to form the ciphertext. For example, “a” becomes “d”, “b” becomes “e”, and so on.
  • 500 AD – Vigenere’s Cipher. Vigenere designed a cipher that is said to have been the first cipher to use a secret key.
  • 1800 Hebern Rotor Machine. In the early 1800s, when everything became electric, Hebern designed an electromechanical device that used a single rotor in which the secret key is embedded in a rotating disk. The key encoded a substitution box and each keystroke on the keyboard resulted in the output of ciphertext. Like the caesar and vigenere ciphers, Hebern’s machine was broken by using letter frequencies.
  • 1918 – Enigma Machine. The Engima machine was invented by German engineer Arthur Scherbius at the end of World War I and was heavily used by German forces during World War II. The Enigma machine used 3 or more rotors that spin at different speeds as you type on the keyboard and output corresponding letters of the ciphertext. In the case of Enigma, the key was the initial setting of the rotors.
  • 1943 Alan Turing and others on his team at Bletchley Park, complete the “Heath Robinson”, a specialized machine for cipher-breaking. This team was also responsible for cracking the Enigma Machine during the second world war.
  • 1948 – Claude Shannon writes a paper that is responsible for establishing our modern mathematical basis of information theory.
  • 1970 – Lucifer Cipher. In the early 1970s, a team from IBM designed a cipher called Lucifer. The Nation Bureau of Standards (now NIST) in the U.S. put out a request for proposals for a block cipher that would become a national standard. Lucifer was eventually accepted and became DES (Data Encryption Standard).
  • 1977 – RSA public key encryption invented by Ron Rivest, Adi Shamir and Leonard Adleman.
  • 1991 – Phil Zimmermann releases PGP.
  • 1994 – Secure Sockets Layer (SSL) encryption protocol released by Netscape, which now secures the majority of the modern web.
  • 1994 – Peter Shor devises an algorithm which lets quantum computers determine the factorization of large integers quickly.
  • 1997 – DES Broken by exhaustive search. In 1997 and the following years, DES was broken by an exhaustive search attack. The main problem with DES was the small size of the encryption key. As computing power increased, it became easy to brute force all the different combinations of the key to get a possible plaintext message.
  • 2000 – AES accepted as DES replacement. In 1997, NIST again put out a request for proposal for a new block cipher. It received 50 submissions. In 2000, it accepted Rijndael, and christened it as AES or the Advanced Encryption Standard.
  • 2004 – MD5 shown to be vulnerable to collisions
  • 2009 – Bitcoin network launch

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