The Jargon File (version 4.4.7, 29 Dec 2003):

cypherpunk
 n.

    [from cyberpunk] Someone interested in the uses of encryption via
    electronic ciphers for enhancing personal privacy and guarding against
    tyranny by centralized, authoritarian power structures, especially
    government. There is an active cypherpunks mailing list at <
    cypherpunks-request@toad.com> coordinating work on public-key encryption
    freeware, privacy, and digital cash. See also tentacle.