Research On The Bitcoin Wallets Supported Offline Payments And Privacy Protection

At present,there exists technical limitation in the wallet used to store Bitcoin.This is mainly reflected in the fact that most wallet software needs to store and backup user's keys in offline transaction.At the same time,it is vulnerable to a type of trapdoor attack.In addition,the pseudonym mechanism of the Bitcoin system only has pseudo anonymity property.The adversary can easily obtain user's transaction privacy information by use of transaction graph analysis or the Change attack.According to whether there exists a third-party platform(such as a shuffling server),the existing methods for improving the anonymity of bitcoin system can be divided into the centralized privacy protection scheme and the decentralized privacy protection scheme.However,these protocols have problems such as limited application scenarios.Therefore,this paper has done the following work on the above issues:(1)The offline wallet in multiple offline bitcoin transactions needs to generate and store a large number of public and private key pairs for users,which impose a heavy storage burden on the wallets and lower the efficiency of the transaction.In addition,the offline wallet is vulnerable to a type of trapdoor attack,like the kleptographic attack,resulting in the leakage of the user's private keys.In view of the above problems,an offline wallet(MOBT)that can quickly execute multiple offline bitcoin transactions is proposed.We generate the key pair of the MOBT wallet by an iterative manner,thereby reducing the key storage space of the wallet under multiple offline bitcoin transactions and making users have a better wallet experience.In addition,we utilize an interactive signature protocol to resist the kleptographic attack.Finally,the protocol propose a novel approach to penalizing double-spending attacker.This measure can be implemented without a trusted third party,which was impossible in the past.(2)In the centralized privacy protection scheme,users need to wait for other people with the same conditions to complete the transaction information hiding process,which limits the large-scale application of existing schemes.In response to this problem,a wallet protocol is proposed to protect the privacy of Bitcoin transactions.It allows a single user to hide transaction information by use of the wallet service,while the government or authorized authority can track the transaction history of illegal users,thus improving the regulatory mechanism of the Bitcoin system.In addition,this protocol solves the problem that the verification process is incomplete in the previous schemes when verifying the correctness of the hidden transaction amounts,thereby ensuring the encrypted transaction amounts are always correct and the payee will not suffer additional losses.Finally,the protocol was analyzed for anonymity and efficiency.(3)In the decentralized privacy protection scheme,users can not request to exit during the bitcoin confusion process.To solve this problem,an anonymous revocation scheme for Bitcoin confusion is proposed.The scheme comprehensively utilizes technical means such as commitment,accumulator and knowledge signatures to effectively resist the knowledge signature forgery attack and the identity detection attack.In addition,the protocol can be implemented without modifying the current Bitcoin system.