An electronic cash system allows users to withdraw coins, represented as bit strings, from a bank or broker, and spend those coins anonymously at participating mer- chants, so that the broker cannot link spent coins to the user who withdraws them. A variety of schemes with var- ious security properties have been proposed for this pur- pose, but because strings of bits are inherently copyable, they must all deal with the problem of double-spending. In this paper, we present an electronic cash scheme that in- troduces a new peer-to-peer system architecture to prevent double-spending without requiring an on-line trusted party or tamper-resistant software or hardware. The scheme is easy to implement, computationally efficient, and prov- ably secure. To demonstrate this, we report on a proof-of- concept implementation for Internet vendors along with a detailed complexity analysis and selected security proofs.