Delegated-Query Oblivious Transfer and its Practical Applications

TL;DR

A compiler that transforms any 1-out-of-n OT into a thin client version that protects privacy in evolving scenarios of physically separated databases, e.g., Internet of Things devices.

Abstract

Databases play a pivotal role in the contemporary World Wide Web and the world of cloud computing. Unfortunately, numerous privacy violations have recently garnered attention in the news. To enhance database privacy, we consider Oblivious Transfer (OT), an elegant cryptographic technology. Our observation reveals that existing research in this domain primarily concentrates on theoretical cryptographic applications, overlooking various practical aspects: - OTs assume parties have direct access to databases. Our "1-out-of-2 Delegated-Query OT" enables parties to privately query a database, without direct access. - With the rise of cloud computing, physically separated databases may no longer remain so. Our "1-out-of-2 Delegated-Query Multi-Receiver OT" protects privacy in such evolving scenarios. - Research often ignores the limitations of thin clients, e.g., Internet of Things devices. To address this, we propose a compiler that transforms any 1-out-of-n OT into a thin client version.

Figures (6)

• Figure 1: DQ-OT: Our $1$-out-of-$2$ OT that supports query delegation. The input of ${R}$ is a private binary index $s$ and the input of ${S}$ is a pair of messages $(m_{ 0}, m_{ 1})$. Note, $\mathtt{SS}\xspace(.)$ is the share-generation algorithm, $\mathtt{H}\xspace(.)$ is a hash function, and $\$$ denotes picking a value uniformly at random.
• Figure 2: DUQ-OT: Our $1$-out-of-$2$ OT that supports query delegation while preserving the privacy of query from ${R}$.
• Figure 3: Phases \ref{['phase::s-init']}--\ref{['DUQOT-HT::gen-res']} of ${\text{DUQ}^{ \text{MR}}\text{--}\text{OT}}$.
• Figure 4: A compiler that turns a $1$-out-of-$n$ OT with response size $O(n)$ to a $1$-out-of-$n$ OT with response size $O(1)$.
• Figure 5: Original OT proposed by Naor and Pinkas Efficient-OT-Naor. In this protocol, the input of ${R}$ is a private binary index $s$ and the input of ${S}$ is a pair of private messages $(m_{ 0}, m_{ 1})$.

Theorems & Definitions (19)

• definition thmcounterdefinition
• definition thmcounterdefinition: $\mathcal{DQ\text{--}OT}^{ 2}_{ 1}$
• definition thmcounterdefinition: Efficiency
• definition thmcounterdefinition: Sender-push communication
• theorem thmcountertheorem
• proof
• definition thmcounterdefinition: $\mathcal{DUQ\text{--}OT}^{ 2}_{ 1}$
• theorem thmcountertheorem
• proof
• definition thmcounterdefinition: $\mathcal{DQ^{ MR}\text{--}OT}^{ 2}_{ 1}$