A provably secure and practical fair E-cash scheme

By analyzing some current fair E-cash schemes, we find they are not always “fair” or “practical”. So we present a new scheme based on group signature with the problems solved. In our improved E-cash system, bank performs “double-spending owner tracing” and trusted authority performs “unconditional owner tracing” and “unconditional coin tracing” when necessary. Then we provide security proofs of our scheme under standard assumptions.