elliptical curve cryptography (ECC) definition

Contributor(s): Jonathan Burr

Elliptical curve cryptography (ECC) is a public key encryption technique based on elliptic curve theory that can be used to create faster, smaller, and more efficient cryptographic keys. ECC generates keys through the properties of the elliptic curve equation instead of the traditional method of generation as the product of very large prime numbers. The technology can be used in conjunction with most public key encryption methods, such as RSA, and Diffie-Hellman. According to some researchers, ECC can yield a level of security with a 164-bit key that other systems require a 1,024-bit key to achieve. Because ECC helps to establish equivalent security with lower computing power and battery resource usage, it is becoming widely used for mobile applications. ECC was developed by Certicom, a mobile e-business security provider, and was recently licensed by Hifn, a manufacturer of integrated circuitry (IC) and network security products. RSA has been developing its own version of ECC. Many manufacturers, including 3COM, Cylink, Motorola, Pitney Bowes, Siemens, TRW, and VeriFone have included support for ECC in their products.

The properties and functions of elliptic curves have been studied in mathematics for 150 years. Their use within cryptography was first proposed in 1985, (separately) by Neal Koblitz from the University of Washington, and Victor Miller at IBM. An elliptic curve is not an ellipse (oval shape), but is represented as a looping line intersecting two axes (lines on a graph used to indicate the position of a point). ECC is based on properties of a particular type of equation created from the mathematical group (a set of values for which operations can be performed on any two members of the group to produce a third member) derived from points where the line intersects the axes. Multiplying a point on the curve by a number will produce another point on the curve, but it is very difficult to find what number was used, even if you know the original point and the result. Equations based on elliptic curves have a characteristic that is very valuable for cryptography purposes: they are relatively easy to perform, and extremely difficult to reverse.

The industry still has some reservations about the use of elliptic curves. Nigel Smart, a Hewlett Packard researcher, discovered a flaw in which certain curves are extremely vulnerable. However, Philip Deck of Certicom says that, while there are curves that are vulnerable, those implementing ECC would have to know which curves could not be used. He believes that ECC offers a unique potential as a technology that could be implemented worldwide and across all devices. According to Deck (quoted in Wired), "the only way you can achieve that is with elliptic curve."

This was first published in September 2005

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