区块链数据库:一种可查询且防篡改的数据库

随着比特币、以太币等一系列加密货币的兴起，其底层的区块链技术受到越来越广泛的关注.区块链有防篡改、去中心化的特性.以太坊利用区块链技术来构建新一代去中心化的应用平台.BigchainDB将区块链技术与传统的分布式数据库相结合，利用基于联盟投票的共识机制改进传统Pow机制中的节点全复制问题，提高了系统的扩展性与吞吐率.但是现有的区块链系统存储的信息大都是固定格式的交易信息，虽然在每个交易里有数据字段，但是现有的区块链系统并不能经由链上对交易内的数据字段的具体细节进行直接查询.如果想要查询数据字段的具体细节，只能先根据交易的哈希值进行查询，得到该交易的完整信息，然后再检索该交易内的数据信息.数据可操作性低，不具备传统数据库的查询功能.首先提出一种区块链数据库系统框架，将区块链技术应用于分布式数据管理；其次提出一种基于哈希指针的不可篡改索引，根据该索引快速检索区块内数据，以此实现区块链的查询；最后，通过实验测试数据库的读写性能，实验结果表明，所提出的不可篡改索引在保证不可篡改的同时具有较好的读写性能.

BlockchainDB: Querable and Immutable Database

With the rise of a series of crypto-currencies, such as Bitcoin and Ether, the underlying blockchain technology has received more and more attention. The blockchain is known as the characteristics of decentralization and immutability. Ethereum utilizes the blockchain technology to build the next generation decentralized application platform. BigchainDB combines blockchain technology with traditional distributed databases, and uses the federal based voting to improve the traditional PoW mechanism and finally improves the system''s scalability and throughput. However, the existing blockchain system mostly stores transaction information with a fixed-form. Although there are data fields in each transaction, the existing blockchain system cannot directly query the specific details within the data fields of the transaction data from the blockchain data. To query the specific details of the data field, it must query the transaction first with the hash value of the transaction to get the complete information of the transaction, and then retrieve the details in the transaction data. This mechanism has a low operability of data and a lack of query functions of the traditional database. This study first proposes a framework of blockchain database system, which applies blockchain technology to distributed data management. Then, an immutable index is proposed based on hash functions. According to the index, the data in the block can be quickly retrieved to implement the query processing in the blockchain. Finally, experiments are designed to test the database''s read/write performance. The experimental results show that the immutable index has good read/write performance while ensuring immutability.