History of Computer Science: Cryptography with Digital Computers

                With the computer revolution came forth more advanced cryptographic techniques that were previously impossible or at the very least not very efficient. In 1948, Claude Shannon started the cryptographic revolution with his paper, A Communications Theory of Secrecy Systems. The published paper crowned Shannon as “The Father of Information Theory” because he applied advanced mathematical techniques to show and prove the security of cryptographic algorithms. The Lucifer cipher developed by Horst Feistel in the 1970’s while working for IBM paved the way for the symmetric key ciphers. By the mid 1970’s the computer revolution was at full strength and it became clear that digital data needed to be secured. At the time cryptography was a field only for the military and the government until the National Bureau of Standards called for cipher proposals. The only serious contender was the Lucifer cipher which the NBS handed to the government experts, the NSA, who modified the Lucifer cipher and created the Data Encryption Standard (DES). With the ever increasing computational powers of the computers over time DES has been replaced by Triple-DES and AES.

                During the same time the symmetric key cryptography was being developed another cryptographic technique was being born, public key cryptography. In 1976, Whitfield Diffie and Martin Hellman published a paper titled New Directions in Cryptography which introduced public key cryptography and one-way functions. Unlike symmetric keys which required the key to be shared before the communication was made, the Diffie-Hellman key exchange allowed making connections without prior key sharing. The one-way functions allowed the public key cryptosystem to flourish because one-way functions are easy to compute in one direction computationally infeasible in the other. The Diffie-Hellman inspired RSA which is stilled used today for public cryptography. RSA was published in 1977 by Ronald L. Rivest, Adi Shamir and Leonard M. Adleman. For internet security PGP was released in 1991 and it is still considered secure today. PGP uses public keys and doesn’t allow the sender to determine the decryption key even if the encryption key is known. Cryptography has become extremely important and will become more important as the power of computers increases along with the growth of digital data and the internet.

More detailed history here and here.

More info on different cryptography systems here.
Book I've been reading: Information Security: Principles and Practice by Mark Stamp.