Abstract:

To address the untrusted issue of cloud storage servers， a Dynamic ciphertext sorting and retrieval scheme based on blockchain was proposed. A balanced binary tree was utilized as the index tree to achieve sublinear search efficiency. A vector space model was employed to reduce text complexity. The sorting of search results for multiple keywords was achieved through the TF-IDF （Term Frequency-Inverse Document Frequency） weighted statistical algorithm. By employing a separate index tree for newly added files and maintaining a revocation list for deleted files， dynamic updating was enabled for the blockchain-based searchable encryption solution. Through leakage function， it is proven that the proposed scheme is secure against adaptive chosen keyword attacks. Performance testing analysis demonstrates that compared to the ｛key， value｝ index structure， the tree index structure adopted in the proposed scheme reduces index tree generation time by 98%， file search time by 7% and dynamic updating time by 99% averagely， with significant efficiency improvements on each step.

Key words: searchable encryption, multi-keyword search, ciphertext sorting, blockchain, index tree

摘要：

为解决云存储服务器不可信问题，提出基于区块链的动态密文排序检索方案。首先，采用树形索引结构，可达到亚线性的检索效率；使用向量空间模型，降低了文本的复杂度；其次，利用词频-逆文档频率（TF-IDF）加权统计算法实现了多关键词检索结果的排序；再次，采用为新添加的文件单独建立索引树、为删除文件建立删除列表的方法，动态更新区块链上可搜索加密方案；最后，通过泄漏函数证明了所提方案对自适应选择关键词攻击的安全性。性能测试结果表明，所提方案采用的树形索引结构相较于｛key，value｝索引结构，索引树生成时间平均降低了98%、文件搜索时间平均降低了7%、动态更新时间平均降低了99%，各阶段效率均有明显提高。

关键词: 可搜索加密, 多关键词搜索, 密文排序, 区块链, 索引树