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Cryptography and Communications

LR-OT: Leakage-resilient oblivious transfer

Francesco Berti, Carmit Hazay, Itamar Levi

Published Jul 21, 2025• 0 citations
Publisher

Abstract

Abstract Oblivious Transfer ( $$\textsf{OT}$$ OT ) is a fundamental cryptographic primitive that becomes a crucial component of a practical secure protocol. $$\textsf{OT}$$ OT is typically implemented in software, and one way to accelerate its running time is by using hardware implementations. However, such implementations are vulnerable to side-channel attacks (SCAs). On the other hand, protecting interactive protocols against SCA is highly challenging due to their longer secrets (which include inputs and randomness), more complex design, and the need to run multiple instances. Consequently, there are no truly practical leakage-resistant $$\textsf{OT}$$ OT protocols yet. In this paper, we introduce two tailored indistinguishability-based security definitions for leakage-resilient $$\textsf{OT}$$ OT , focusing on protecting the sender’s state. Second, we propose a practical semi-honest secure $$\textsf{OT}$$ OT protocol that achieves these security levels while minimizing the assumptions on the protocol’s building blocks and the use of a secret state.

DOI
10.1007/s12095-025-00824-4

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Abstract Oblivious Transfer ( OT\textsf{OT}OT OT ) is a fundamental cryptographic primitive that becomes a crucial component of a practical secure protocol. OT\textsf{OT}OT OT is typically implemented in software, and one way to accelerate its running time is by using hardware implementations. However, such implementations are vulnerable to side-channel attacks (SCAs). On the other hand, protecting interactive protocols against SCA is highly challenging due to their longer secrets (which include inputs and randomness), more complex design, and the need to run multiple instances. Consequently, there are no truly practical leakage-resistant OT\textsf{OT}OT OT protocols yet. In this paper, we introduce two tailored indistinguishability-based security definitions for leakage-resilient OT\textsf{OT}OT OT , focusing on protecting the sender’s state. Second, we propose a practical semi-honest secure OT\textsf{OT}OT OT protocol that achieves these security levels while minimizing the assumptions on the protocol’s building blocks and the use of a secret state.
Oblivious Transfer (OT) is a fundamental cryptographic protocol with applications in secure Multi-Party Computation, Federated Learning, and Private Set Intersection. With the advent of quantum computing, it is crucial to develop unconditionally secure core primitives like OT to ensure their continued security in the post-quantum era. Despite over four decades since OT's introduction, the literature has predominantly relied on computational assumptions, except in cases using unconventional methods like noisy channels or a fully trusted party. Introducing "Supersonic OT", a highly efficient and unconditionally secure OT scheme that avoids public-key-based primitives, we offer an alternative to traditional approaches. Supersonic OT enables a receiver to obtain a response of size O(1). Its simple (yet non-trivial) design facilitates easy security analysis and implementation. The protocol employs a basic secret-sharing scheme, controlled swaps, the one-time pad, and a third-party helper who may be corrupted by a semi-honest adversary. Our implementation and runtime analysis indicate that a single instance of Supersonic OT completes in 0.35 milliseconds, making it up to 2000 times faster than the state-of-the-art base OT.
Oblivious transfer (OT) is one of the most fundamental primitives in cryptography and is widely used in protocols for secure two-party and multi-party computation. As secure com-putation becomes more practical, the need for practical large scale oblivious transfer protocols is becoming more evident. Oblivious transfer extensions are protocols that enable a relatively small number of “base-OTs ” to be utilized to compute a very large number of OTs at low cost. In the semi-honest setting, Ishai et al. (CRYPTO 2003) presented an OT extension protocol for which the cost of each OT (beyond the base-OTs) is just a few hash function operations. In the malicious setting, Nielsen et al. (CRYPTO 2012) presented an efficient OT extension protocol for the setting of active adversaries, that is secure in the random oracle model. In this work, we present an OT extension protocol for the setting of malicious adversaries that is more efficient and uses less communication than previous works. In addition, our protocol can be proven secure in both the random oracle model, and in the standard model with a type of correlation robustness. Given the importance of OT in many secure computation protocols, increasing the efficiency of OT extensions is another important step forward to making secure
The Oblivious Transfer (OT), introduced by Rabin in 1981, has become an important and fundamental cryptography technique. An OT protocol should have two important characteristics: sender's privacy and chooser's privacy. The sender is a party who will deliver a secret to chooser. The chooser is another party who acts as receiver to learn some information about input from sender. The chooser learns of certain information concerning sender's input while sender is not allowed to know what chooser has learned. Moreover, chooser cannot acquire any messages that he/she did not choose. Naor and Pinkas have recently proposed an efficient oblivious transfer protocol (EOT) that implementes 1-out-of-n protocol, but this EOT has a flaw: it cannot withstand the same message attack. In this paper, we will improve Naor and Pinkas EOT and make it resistant to the same message attack.
In an adaptive oblivious transfer (OT) protocol, a sender commits to a database of messages and then repeatedly interacts with a receiver in such a way that the receiver obtains one message per interaction of his choice (and nothing more) while the sender learns nothing about any of the choices. Recently, there has been significant effort to design practical adaptive OT schemes and to use these protocols as a building block for larger database applications. To be well suited for these applications, the underlying OT protocol should: (1) support an efficient initialization phase where one commitment can support an arbitrary number of receivers who are guaranteed of having the same view of the database, (2) execute transfers in time independent of the size of the database, and (3) satisfy a strong notion of security under a simple assumption in the standard model. We present the first adaptive OT protocol simultaneously satisfying these requirements. The sole complexity assumption required is that given (g, g a, g b, g c, Q), where g generates a bilinear group of prime order p and a, b, c are selected randomly from Zp, it is hard to decide if Q = g abc. All prior protocols in the standard model either do not meet our efficiency requirements or
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 III-(OT)2(OT)^2(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, III-(OT)2(OT)^2(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 III-(OT)2(OT)^2(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 μs on desktop platforms and 39.90 μs on IoT devices, more than 10×\times× faster than the well known SimplestOT.
Oblivious Transfer (OT) protocol is nowadays recognised as a generic primitive for all cryptographic protocols since it is one of the strongest primitives for secure multiparty computation (MPC). To design hardware-assisted OT protocols, Physically Unclonable Functions (PUFs) have been thoroughly studied in the literature. PUF-based OT protocols, however, necessitate the physical transfer of PUF devices, rendering them inappropriate in situations where the physical transfer of devices is not secure. Additionally, two-party secure computation protocols, in general, are performed between two distrusting parties. Yet, the PUF-based OT protocols require the PUF receiver to trust the PUF sender to behave honestly. Recent works have considered malicious PUF models resulting in more complex protocols. To avoid these drawbacks, we in this work rely on the concept of Physically Related Functions (PReFs), a pair of PUF devices that allow two PUF devices to generate similar responses over a "related" input set. XOR composition of PReFs, also called XOR_PReF, is an improved construction that eliminates the need for any trusted party and generates a "related" input set securely and independently. With the help of this new primitive, we propose 1-out-of-2 OT protocols using XOR_PReF in semi-honest as well as malicious settings keeping the protocol secure even after switching the roles of OT-sender and OT-receiver. Our protocols can be integrated into hardware-assisted MPC protocols and provide a safe and valuable solution for all OT-based techniques, notably Private Set Intersection (PSI), Private Information Retrieval (PIR), and Password Authenticated Key Exchange (PAKE).