Abstract: As a kind of cryptocurrency, bitcoin has attracted much attention with its decentralization. However, there is two problems in the bitcoin transactions: the account security and transaction privacy. In view of the above problems, a new partially blind threshold signature scheme is proposed, which can both enhance the security of bitcoin account and preserve the privacy of transaction. Firstly, transaction amounts are encrypted by employing the homomorphic Paillier cryptosystem, and output address is disturbed by using one-time public key. Then the encrypted or disrupted transaction information is signed by multiple participants who are authorized by using threshold secret sharing. Compared with partially blind fuzzy signature scheme, the proposed scheme can fully preserve the transaction privacy. Furthermore, performance analysis shows that the proposed scheme is secure and effective in practical applications.

Key words: bitcoin, account security, threshold secret sharing, transaction privacy, one-time public key, Paillier cryptosystem