In data outsourcing services, to ensure data security and user privacy, data is usually stored in cloud servers in ciphertext form. This method makes users face the problem of how to search the keywords in the ciphertexts. Although the Dynamic Searchable Symmetric Encryption (DSSE) schemes can solve this problem, most DSSE schemes assume that all the data is stored in a single cloud server. The assumption is not realistic since data may be stored in multiple servers. Furthermore, the cloud servers are usually considered “honest-but-curious”, though malicious servers can actively attack and return incomplete or incorrect results. In this paper, we propose a Blockchain-based DSSE under the Multiple Clouds (BDSSE-MC) scheme. The scheme enables the data owner to generate encrypted local file indexes and merges the local indexes into a global index through a smart contract. The search operation is also performed by the smart contract based on the global index. In this scheme, the attacker cannot obtain the original files and search results, only knows the number of clouds and the number of files. We provide security and privacy analysis. We also compare the experiments results with those of traditional solutions.

在数据外包服务中，为保证数据安全和用户隐私，数据通常以密文形式存储在云服务器中。这种方法使用户面临如何在密文中搜索关键字的问题。虽然动态可搜索对称加密 (DSSE) 方案可以解决这个问题，但大多数 DSSE 方案都假设所有数据都存储在单个云服务器中。该假设是不现实的，因为数据可能存储在多个服务器中。此外，尽管恶意服务器可以主动攻击并返回不完整或不正确的结果，但通常认为云服务器是“诚实但好奇的”。在本文中，我们提出了多云（BDSSE-MC）方案下基于区块链的 DSSE。该方案使数据所有者能够生成加密的本地文件索引，并通过智能合约将本地索引合并为全局索引。搜索操作也由智能合约根据全局索引执行。在该方案中，攻击者无法获得原始文件和搜索结果，只能知道云的数量和文件的数量。我们提供安全和隐私分析。我们还将实验结果与传统解决方案的结果进行了比较。