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arXiv 2303.09043cs.CR
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HE is all you need: 使用加性 HE 压缩 FHE 密文

HE is all you need: Compressing FHE Ciphertexts using Additive HE

Rasoul Akhavan Mahdavi, Abdulrahman Diaa, Florian Kerschbaum

AI总结:

针对高延迟网络下同态加密密文通信开销大的问题,提出利用加性同态加密压缩基于LWE的大型密文的技术,实现超99%压缩率,并据此构建了通信开销最低且无需预处理通信的ZipPIR协议。

摘要:

同态加密(HE)是构建隐私保护应用的常用工具。然而,在具有许多客户端和高延迟网络的场景中,由巨大密文尺寸引发的通信开销成为了瓶颈。在本文中,我们提出了一种新的压缩技术,该技术使用具有小密文的加性同态加密方案,来压缩基于 Learning with Errors (LWE) 的大型同态密文。我们的技术利用此类密文解密过程中的线性步骤,将部分解密工作委托给服务器。我们实现了高达 90% 的压缩率,且仅需一个小的压缩密钥。通过同时压缩多个密文,我们可以达到超过 99% 的压缩率。我们的压缩技术可以直接应用于将 LWE 密文从服务器传输至客户端作为查询响应的应用中。此外,我们将该技术应用于私有信息检索(PIR),在该场景中客户端访问数据库而不会泄露其查询内容。利用我们的压缩技术,我们提出了 ZipPIR,这是一种 PIR 协议,在现有文献的所有协议中实现了最低的整体通信开销。ZipPIR 在预处理阶段不需要与客户端进行任何通信,这使其成为具有临时客户端或高延迟网络的 PIR 用例的理想解决方案。

英文摘要:

Homomorphic Encryption (HE) is a commonly used tool for building privacy-preserving applications. However, in scenarios with many clients and high-latency networks, communication costs due to large ciphertext sizes are the bottleneck. In this paper, we present a new compression technique that uses an additive homomorphic encryption scheme with small ciphertexts to compress large homomorphic ciphertexts based on Learning with Errors (LWE). Our technique exploits the linear step in the decryption of such ciphertexts to delegate part of the decryption to the server. We achieve compression ratios up to 90% which only requires a small compression key. By compressing multiple ciphertexts simultaneously, we can over 99\% compression rate. Our compression technique can be readily applied to applications which transmit LWE ciphertexts from the server to the client as the response to a query. Furthermore, we apply our technique to private information retrieval (PIR) where a client accesses a database without revealing its query. Using our compression technique, we propose ZipPIR, a PIR protocol which achieves the lowest overall communication cost among all protocols in the literature. ZipPIR does not require any communication with the client in the preprocessing phase, making it a great solution for use cases of PIR with ephemeral clients or high-latency networks.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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