Partially Blind ECDSA Scheme and Its Application to Bitcoin

Blind signatures allow a user to obtain a signature without revealing message information to the signer. However, in many cases, the signer must record additional information relevant to the signature. Therefore, the concept of partially blind signature is introduced that enables the signer to obtain some information from the signed message. With the development of blockchain technology, users increasingly use Bitcoin for purchases and transactions with coin providers. Some studies have indicated that Elliptic Curve Digital Signature Algorithm (ECDSA)-based blind signatures are compatible with Bitcoin because they prevent the linking of sensitive information due to the untamability of Bitcoin. However, these approaches are not sufficiently flexible because blind signatures do not allow the signer to obtain any information. Here, we propose an ECDSA-based partially blind signature scheme. Security proofs are provided to demonstrate that the proposed scheme have satisfactory unforgeability and blindness. To the best of our knowledge, compared with other state-of-the-art schemes, our scheme is the first ECDSA-based partially blind signature scheme compatible with the current Bitcoin protocol.