Public Cryptography and Private Key - Private-key Cryptography, Public-key Cryptography, The Cryptographic Outlook

Cryptography—called "crypto" by its practitioners—is the study of codes and ciphers and their use to protect information. Cryptography has existed, in one form or another, since the ancient Greeks began toying with methods for encoding with mathematics. In the modern period, cryptography was utilized mainly in wartime to protect sensitive military information, and in the high-stakes and secretive world of diplomacy and spying.

For years, computer-based cryptography was almost exclusively used by the United States National Security Agency (NSA) for coding and decoding sensitive information and messages during the Cold War. For many years after private-sector computer scientists began working on cryptography, the government fought such efforts out of concern for national security. Cryptographers, however, were wary of government monopolization of the technology, which raised fears of a "big brother" capable of snooping into the private lives and communications of its citizens.

This door was opened in 1975 by Massachusetts Institute of Technology graduate Whitfield Diffie and Stanford University professor Martin Hellman. The two were searching for a way to share encrypted messages between two people who didn't know each other, and thus couldn't have devised their own scrambling formula beforehand. The Diffie-Hellman algorithm that resulted was the birth of contemporary public-key cryptography, the dominant cryptographic infrastructure used on the Internet.

Cryptography assumed a whole new significance with the development of e-commerce in the mid-1990s. Perhaps the biggest roadblocks to e-commerce were consumer fears over privacy and the security of their financial and personal information. Because of this, cryptography was of central importance to the growth of the Internet economy.

Encryption is the scrambling of text-based messages into unrecognizable code via a complex mathematical algorithm. Only those with the correct "key" are able to encrypt or decrypt such a message in a given cryptographic system. The key is a set of specific parameters, based on the algorithmic encryption formula, that act to lock and unlock the coded information. The formula typically consists of a long string of bits, sometimes more than 200 digits long. The more digits involved and the more complicated the algorithmic equation used to generate the code, the more difficult the hacker's job in breaking it.

The two basic infrastructures used in cryptographic systems are public-key and private-key. While early computer systems used private-key cryptography almost exclusively, by the late 1990s and early 2000s the tide was shifting in favor of public-key cryptography. The dominant encryption standards were testament to the sea of change. The 25-year-old Data Encryption Standard (DES), a private-key algorithm developed by the NSA, was being phased out due to its lack of flexibility and a level of security that could no longer withstand sophisticated modern attacks, not to mention the limited use of private-key systems in e-commerce. In its place, the public-key Advanced Encryption Standard (AES) was preparing for international launch in the early 2000s.