David Chaum

In 1981 Chaum described the mix network: messages are encrypted in layers and passed through a chain of servers, each peeling off one layer and shuffling the order, so no single server can link sender to recipient. It is the ancestor of anonymous remailers and, via onion routing, of Tor. The following year came blind signatures — a bank can sign a coin without seeing it, see RSA blinding — and in 1988 the dining cryptographers problem.

Blind signatures underpinned ecash and DigiCash, founded in Amsterdam in 1989 and bankrupt by 1998: the technology worked, but banks didn't want anonymous money. The cypherpunks, and later Bitcoin, picked up where he left off.