The Clipper Encryption System
Dorothy E. Denning · American Scientist · 1993
Cryptography is an ancient art. During the Gallic Wars in the first century b.c.e. Julius Caesar encoded his messages by shifting the alphabet forward by three letters, so that an A was encoded as a D and so on. Over the centuries since then, increasingly complicated encryption systems have been developed in an ongoing ef? fort to outsmart the code breakers. Sophisticated encryption technology will soon be so widely available that it will be used to hide illegal activi? ties, and no law-enforcement agencies will be able to unravel the evidence behind encrypted crimes. The Clinton administration wants to prevent a possible cryptographic edge for criminals by de? veloping a key-escrow system of encryption for voice and data communications. On April 16, President Clinton proposed a new government standard for encryption. It is embodied in two mi? croelectronic devices called the Clipper Chip and the Capstone Chip. Many encryption systems, including the Clipper and Capstone chips, rely a for encoding and decoding a message. Caesar's encryption sys? tem used a key of 3, and an encryptographic algo? rithm of adding on followed by letter substitu? tion. Modern encryption systems use a stream of numbers, or bits, as the key and an algorithm com? posed of a series of mathematical transformations. A longer key coupled with a complex algorithm makes an encryption system more difficult to break. The mid-1970s marked a turning point in the development of modern cryptosystems. In 1976 Whitneld Difhe and Martin Hellman of Stanford University introduced the public-key cryptosys tem. This system relies matched pairs of keys, one public and the other secret. A sender can en? code a message with a receiver's public key, and