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arXiv 1707.02152cs.ITmath.IT
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安全的对称私有信息检索

Secure Symmetric Private Information Retrieval from Colluding Databases with Adversaries

Qiwen Wang, Mikael Skoglund

摘要:

研究了服务器和对手合谋情况下的对称私有信息检索(SPIR)问题。具体地,数据库包括$K$文件,其被复制地存储在$N$服务器之间。用户希望通过与$N$服务器通信从数据库中检索一个文件,而不向任何服务器透露所需文件的身份。此外,用户不应了解其他$K-1$文件。$N$服务器中的任何$T$都可能串通,也就是说,它们可能会与用户进行交互,以猜测所请求文件的身份。系统中的对手可以窃听甚至试图破坏通信。考虑了三种类型的对手:拜占庭对手,可以覆盖任何$B$服务器向用户的传输;被动窃听者,可以窃听任何$E$服务器的传入和传出传输;以及两者的组合-可以窃听一组任何$E$节点的对手,并覆盖一组任何$B$节点的传输。将存在合谋服务器和三类攻击者的SPIR问题分别命名为T-BSPIR、T-ESPIR和T-BESPIR。问题的容量被定义为每个下载位检索到的所需文件的最大信息位数。我们表明,T-BSPIR等于$1-\frac{2B+T}{N}$的信息理论容量,如果服务器共享共同的随机性(在用户不可用)的金额至少$\frac{2B+T}{N-2B-T}$倍的文件大小。否则,容量等于零。证明了T-ESPIR的容量等于$1-\frac{\max(T,E)}{N}$,公共随机性至少是文件大小的$\frac{\max(T,E)}{N-\max(T,E)}$倍。最后证明了T-BESPIR的容量为$1-\frac{2B+\max(T,E)}{N}$,公共随机性至少为文件大小的$\frac{2B+\max(T,E)}{N-2B-\max(T,E)}$倍。

英文摘要:

The problem of symmetric private information retrieval (SPIR) from replicated databases with colluding servers and adversaries is studied. Specifically, the database comprises $K$ files, which are replicatively stored among $N$ servers. A user wants to retrieve one file from the database by communicating with the $N$ servers, without revealing the identity of the desired file to any server. Furthermore, the user shall learn nothing about the other $K-1$ files. Any $T$ out of $N$ servers may collude, that is, they may communicate their interactions with the user to guess the identity of the requested file. An adversary in the system can tap in on or even try to corrupt the communication. Three types of adversaries are considered: a Byzantine adversary who can overwrite the transmission of any $B$ servers to the user; a passive eavesdropper who can tap in on the incoming and outgoing transmissions of any $E$ servers; and a combination of both -- an adversary who can tap in on a set of any $E$ nodes, and overwrite the transmission of a set of any $B$ nodes. The problems of SPIR with colluding servers and the three types of adversaries are named T-BSPIR, T-ESPIR and T-BESPIR respectively. The capacity of the problem is defined as the maximum number of information bits of the desired file retrieved per downloaded bit. We show that the information-theoretical capacity of T-BSPIR equals $1-\frac{2B+T}{N}$, if the servers share common randomness (unavailable at the user) with amount at least $\frac{2B+T}{N-2B-T}$ times the file size. Otherwise, the capacity equals zero. The capacity of T-ESPIR is proved to equal $1-\frac{\max(T,E)}{N}$, with common randomness at least $\frac{\max(T,E)}{N-\max(T,E)}$ times the file size. Finally, the capacity of T-BESPIR is proved to be $1-\frac{2B+\max(T,E)}{N}$, with common randomness at least $\frac{2B+\max(T,E)}{N-2B-\max(T,E)}$ times the file size.

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