区块链与可搜索加密结合的电子病历共享方案

电子病历（Electronic Medical Record，EMR）数据的共享被认为是提高医疗服务质量和降低医疗成本的关键方法。然而，EMR分散存储在各个医疗机构中，这阻碍了数据共享，并使患者的隐私面临风险。为了解决这些问题，提出了一个基于区块链的EMR隐私保护数据共享方案。将原始EMR安全地存储在私有链中，而将关键词索引保存在联盟链中，从而有效降低医疗数据泄露的风险，并保证EMR的不可篡改性。利用布尔函数改进基于密文策略属性的关键字搜索算法，用属性上的布尔公式指定表达性访问策略，有效优化了带宽和通信消耗，并引入了门限签名机制，有效地缩短了密文长度。使用私有链服务器执行配对操作，使得搜索速度更快。通过公共验证者检查搜索结果，保证了数据安全并降低了计算开销。安全性和性能分析的结果表明，该方案是实现EMR数据共享的一种安全有效的方法，可减轻用户设备的额外计算负担，最小化带宽和通信消耗。

Electronic Medical Record Sharing Scheme Based on Blockchain and Searchable Encryption

The sharing of Electronic Medical Record（EMR） data is considered to be the fundamental method to improve the quality of medical service and reduce medical costs. However, EMR is stored in various medical institutions, which hinders data sharing and put patients’ privacy at risk. To solve these problems, an EMR privacy preserving data sharing scheme based on blockchain is proposed. The original EMR is stored securely in the private blockchain, while the keyword index is stored in the consortium blockchain, so as to effectively reduce the risk of medical data leakage and ensure the non tamperability of EMR. The Boolean function is used to improve the keyword search algorithm based on the attribute of ciphertext policy, and the Boolean formula on the attribute is used to specify the expressive access policy, which effectively optimizes the bandwidth and communication consumption. The threshold signature mechanism is introduced to shorten the length of ciphertext. The private blockchain server is used to perform pairing operation, which makes the search faster. The public verifier checks the search results to ensure the data security and reduce the computational overhead. Through the security analysis and performance analysis, it shows that this scheme is a safe and effective way to realize EMR data sharing, which reduces the additional computing burden of user equipment with limited resources, and further minimizes the bandwidth and communication consumption.