Alan Freedman -- The Computer Language Company - Computer Desktop Encyclopedia
Computer Desktop Encyclopedia
Longest-Running Tech Reference on the Planet

A CDE Definition

You'll love The Computer Desktop Encyclopedia (CDE) for Tech Term of the Day (TTOD)



A cryptographic key exchange method developed by Whitfield Diffie and Martin Hellman in 1976. Also known as the "Diffie-Hellman-Merkle" method and "exponential key agreement," it enables parties at both ends to derive a shared, secret key without ever sending it to each other.

Using a common number, both sides use a different random number as a power to raise the common number. The results are then sent to each other. The receiving party raises the received number to the same random power they used before, and the results are the same on both sides. See elliptic curve cryptography and key management.

Very Clever
There is more computation in actual practice, but this example, which uses tiny numbers to illustrate the concept, shows a very clever mathematical approach. Each party raises the common number, which is 2 in this example (this has nothing to do with binary-- it is just the number "2") to a random power and sends the result to the other. The received number is raised to the same random power. Note that both parties come up with the same secret key, which was never transmitted intact.

Personal Use Only

Before/After Your Search Term
differential amplifierDiffie-Helman
Differential Analyzerdiffraction
differential backupdiffraction grating
differential configurationDiffserv
differential GPSdiffusion
differential PCMDig
Differential SCSIdigerati
differential signalingdigest
differential updatingDigg
differentiated servicesDiggs

Terms By Topic
Click any of the following categories for a list of fundamental terms.
Computer Words You Gotta KnowSystem design
Job categoriesUnix/Linux
Interesting stuffPersonal computers
InternetIndustrial Automation/Process Control
Communications & networkingAssociations/Standards organizations
HistoryDesktop publishing
ProgrammingHealthcare IT
System design