Diffie, Whitfield

In 1976, Whitfield Diffie developed public-key encryption as an alternative to private-key encryption. Public-key encryption is based on two halves of the same key that are generated with special software at the same time. The key pair are mathematically related so that the private key cannot be determined from the public key. Only one of the two halves of the key pair is required to encrypt a message, with the other half being used for decryption. In public key cryptography, one half of the key pair (the private key) is assigned to an individual, and is closely guarded and securely stored on the user s local disk in either an encrypted format or as part of a token that interfaces with the computer. The other half of the key is published in a public directory where all users can access it and this therefore referred to as the public key. 

DiHe76 Whitfield Diffie, Martin E. Heilman New Directions in Cryptography IEEE Transactions on Information Theory 22/6 (1976) 644-654. 

When DES was standardized, Whitfield Diffie and Martin Heilman estimated that it would be possible to build a DES-cracking computer for 20 million that would crack a DES key in a day. In 1993, Michael Wiener designed on paper a special purpose brute force DES-cracking computer that he estimated could be built for 1 million and would crack an average DES key in about three and a half hours. In 1997, Wiener updated his analysis based on then-current computers, estimating that a 1 million machine would crack keys in 35 minutes. 

The concept of public key cryptography was originally proposed in 1976 by Whitfield Diffie and Martin Heilman, and independently by Ralph Merkle. In 1997, Britain s Government Communications Headquarters (GCHQ) released previously classified documents revealing three British government employees, James Ellis, Clifford Cocks, and Malcolm Williamson, developed these same ideas several years earlier, but kept them secret for reasons of national security. There is some evidence that the United States National Security Agency (NSA)... 

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