Private Information Retrieval (PIR) with Alex Hoover

In this episode, Anna and Kobi are joined by Alex Hoover, cryptographer and Assistant Professor at Stevens Institute of Technology. They explore Private Information Retrieval (PIR)—a cryptographic primitive that lets users query public databases without revealing what they're looking for.

They trace PIR's evolution from its early theoretical foundations to modern, practical constructions, unpack key variants like batch and keyword PIR, and discuss emerging blockchain applications, from private state queries to Merkle proof generation. They also examine the latest research making PIR increasingly practical, and why it could become a core building block for privacy-preserving systems.

A quick note: Alex mentioned during the interview that preprocessing in SimplePIR is independent of the database. But it is in fact independent of the queried index, and does depend on the database. He asked us to highlight this correction

Related Links

• One Server for the Price of Two: Simple and Fast Single-Server Private Information Retrieval
• Don’t be Dense: Efficient Keyword PIR for Sparse Databases
• The two papers that introduced client-side preprocessing:
  • PPY18
  • CK20
  
  
• Piano: Extremely Simple, Single-Server PIR with Sublinear Server Computation 
• Simple and Practical Amortized Sublinear Private Information Retrieval using Dummy Subsets 
• Plinko: Single-Server PIR with Efficient Updates via Invertible PRFs (builds on Piano and RMS) 
• Doubly Efficient Private Information Retrieval and Fully Homomorphic RAM Computation from Ring LWE (LMW23) 
• Lower Bounds for PIR with Preprocessing from Blackbox Cryptography

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