# I-(OT)^2: A Client-optimal Oblivious Transfer Protocol for IoT Devices Source: [I-(OT)^2: A Client-optimal Oblivious Transfer Protocol for IoT Devices]() Collection index: [llms.txt]() Data updated: 2026-06-02T05:03:19.764Z Authors: Elia Onofri, Andrea Ciccotelli, Roberto Di Pietro Published: 2026-06-01T14:54:08.000Z ## Abstract Oblivious Transfer (OT) is a fundamental cryptographic primitive enabling privacy-preserving computation and constitutes a core building block for secure multi-party computation while supporting a wide range of security-sensitive applications: private information retrieval, zero-knowledge proofs, and password-authenticated key exchange, to cite a few. While recent advances in OT extension have significantly reduced amortised costs, their reliance on batches of random base OTs and substantial pre-computation phases limits their practicality in scenarios where the number of transfers is modest or where communication latency and client-side computation are critical constraints. In such settings, efficient base OT protocols remain both relevant and necessary. In this work, we introduce $I$-$(OT)^2$, a novel base 1-out-of-2 OT protocol grounded in the quadratic residuosity problem, specifically designed to minimise receiver-side computation and interaction. Our construction is particularly appealing on client--server architectures in which the receiver operates on low-power hardware, such as Internet of Things (IoT) devices. Through a lightweight offline pre-computation phase, $I$-$(OT)^2$ shifts the on-transfer computational burden almost entirely to the Sender, while reducing online communication to only six messages and four digests exchanged. We provide a detailed description of the protocol, accompanied by a formal proof of its security. Moreover, to demonstrate the viability of $I$-$(OT)^2$, we also present an open-source proof-of-concept implementation (in C language) evaluated on real IoT hardware. Results are staggering: for 128-bit security using a 3072-bit RSA modulus, the receiver incurs an average online cost per OT as low as 2.80 {\\mu}s on desktop platforms and 39.90 {\\mu}s on IoT devices, more than 10$\\times$ faster than the well known SimplestOT. ## Recorded benchmark results A research result applies to its stated dataset, split, metric and evaluation configuration. Compare like-for-like settings, preserve the metric's unit and direction, and distinguish paper-reported results from independent reproduction. The best result recorded here is not a claim of exhaustive, current global coverage. - [Oblivious Transfer on OT protocols from literature](): Oblivious Transfer; OT protocols from literature; Communication Rounds: 2. ## Original sources and implementation [Original paper]() [PDF]()