My assumption is that most references to the concept of electronic cash before Bitcoin refer to Chaumian tokens, or at least systems with properties like it.
Chaumian tokens are created by a central server, following this procedure. As an example, say party A has a coin (a random string R1, plus a valid signature S1 from the central server), and wishes to pay party B:
- Party A sends the coin (R1, S1) to B.
- Party B anonymously connects to the central server (for example though Tor), and hands the server (R1, S1), and also sends a newly generated random string R2 in blinded form (R2').
- The central server verifies that S1 is a valid signature, and that R1 was never spent before, marks R1 as spent in a (growing) database, and creates a signature S2' on the blinded string R2', sending it back to B.
- B now removes the blinding from S2', and obtains a new valid coin (R2,S2), which nobody else has.
The security of this scheme relies on the server not knowing what it is signing. So it cannot track (even pseudonymous) ownership of coins. In fact, the server doesn't actually know what coins exist at all, just which ones have been spent.
Schemes like this have very different properties than Bitcoin (and in fact would be a nice complement to it):
- It is extremely centralized (everything depends on the central server).
- As long as anonymously connecting to the server is possible, it has very good privacy. Nobody (including the server) basically observes any transaction except their own.
- Is very scalable (only the server needs to create many signatures, and maintain a database of spent coins).