From Jargon File (4.3.1, 29 Jun 2001) :
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
coordinating work on public-key
encryption freeware, privacy, and digital cash. See also tentacle.