Ashwin Jain, C Hari
This paper presents a new efficient protocol for k-out-of-n oblivious transfer which is a generalization of Parakh's 1-out-of-2 oblivious transfer protocol based on Diffie-Hellman key exchange. In the proposed protocol, the parties involved generate Diffie-Hellman keys obliviously and then use them for oblivious transfer of secrets.
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A new protocol for 1-2 (String) Oblivious Transfer is proposed. The protocol uses 5 rounds of message exchange.
This paper presents protocols for Kak's cubic transformation and proposes a modification to Diffie-Hellman key exchange protocol in order to achieve asymmetric oblivious exchange of keys.
With oblivious transfer multiparty protocols become possible even in the presence of a faulty majority. But all known protocols can be aborted by just one disruptor. This paper presents more robust solutions for multiparty protocols with oblivious transfer. This additional robustness against disruptors weakens the security of the protocol and the guarantee that the result is correct. We can observe a trade off between robustness against disruption and security and correctness. We give an application to quantum multiparty protocols. These allow the implementation of oblivious transfer and the p…
Although random sequences can be used to generate probability events, they come with the risk of cheating in an unsupervised situation. In such cases, the oblivious transfer protocol may be used and this paper presents a variation to the DH key-exchange to serve as this protocol. A method to verify the correctness of the procedure, without revealing the random numbers used by the two parties, is also proposed.
Key-exchange protocols have been overlooked as a possible means for implementing oblivious transfer (OT). In this paper we present a protocol for mutual exchange of secrets, 1-out-of-2 OT and coin flipping similar to Diffie-Hellman protocol using the idea of obliviously exchanging encryption keys. Since, Diffie-Hellman scheme is widely used, our protocol may provide a useful alternative to the conventional methods for implementation of oblivious transfer and a useful primitive in building larger cryptographic schemes.
In this short note we want to introduce {\em anonymous oblivious transfer} a new cryptographic primitive which can be proven to be strictly more powerful than oblivious transfer. We show that all functions can be robustly realized by multi party protocols with {\em anonymous oblivious transfer}. No assumption about possible collusions of cheaters or disruptors have to be made. Furthermore we shortly discuss how to realize anonymous oblivious transfer with oblivious broadcast or by quantum cryptography. The protocol of anonymous oblivious transfer was inspired by a quantum protocol: the anonymo…
This paper proposes an algorithm for oblivious transfer using elliptic curves. Also, we present its application to chosen one-out-of-two oblivious transfer.
ODoQ: Oblivious DNS-over-QUIC
ODoQ通过结合QUIC协议和中间代理服务器，在保护用户隐私和降低解析延迟之间取得平衡。
Oblivious transfer is a primitive of paramount importance in cryptography or, more precisely, two- and multi-party computation due to its universality. Unfortunately, oblivious transfer cannot be achieved in an unconditionally secure way for both parties from scratch. Therefore, it is a natural question what information-theoretic primitives or computational assumptions oblivious transfer can be based on. The results in our thesis are threefold. First, we present a protocol that implements oblivious transfer from a weakened oblivious transfer called universal oblivious transfer, where one of th…
We present an oblivious transfer (OT) protocol that combines the OT scheme of Chou and Orlandi together with thesupersingular isogeny Diffie-Hellman (SIDH) primitive of De Feo, Jao, and Plût. Our construction is a candidate for post-quantum secure OT and demonstrates that SIDH naturally supports OT functionality. We consider the protocol in the simplest configuration of $\binom{2}{1}$-OT and analyze the protocol to verify its security.
We present Path ORAM, an extremely simple Oblivious RAM protocol with a small amount of client storage. Partly due to its simplicity, Path ORAM is the most practical ORAM scheme known to date with small client storage. We formally prove that Path ORAM has a O(log N) bandwidth cost for blocks of size B = Omega(log^2 N) bits. For such block sizes, Path ORAM is asymptotically better than the best known ORAM schemes with small client storage. Due to its practicality, Path ORAM has been adopted in the design of secure processors since its proposal.
Computationally Differentially Private Inner Product Protocols Imply Oblivious Transfer
本文证明任何能在±1域上以O(n^{1/6})加性误差估计内积的计算差分隐私协议都可构造不经意传输，从而确立次多项式准确性协议与不经意传输的等价性，改进前人仅证明密钥协商必要性的结果。
We show that stand-alone statistically secure random oblivious transfer protocols based on two-party stateless primitives are statistically universally composable. I.e. they are simulatable secure with an unlimited adversary, an unlimited simulator and an unlimited environment machine. Our result implies that several previous oblivious transfer protocols in the literature which were proven secure under weaker, non-composable definitions of security can actually be used in arbitrary statistically secure applications without lowering the security.
Oblivious transfer protocols (R-OT and OT$_{1}^{2}$) are presented based on non-orthogonal states transmission, and the bit commitment protocols on the top of OT$_{1}^{2}$ are constructed. Although these OT protocols are all unconditional secure, the bit commitment protocols based on OT protocols are not secure against attack similar to that presented by no-go theorem.
Commitment Schemes from OWFs with Applications to Quantum Oblivious Transfer
针对量子不经意传输（qOT）协议中现有承诺方案带宽与计算成本高的问题，本文扩展Naor承诺方案提出基于单向函数的2比特字符串承诺方案，并设计带预处理的交互式字符串承诺方案，提升qOT中承诺方案的效率。
Quantum protocols for Rabin oblivious transfer
本文针对Rabin不经意传输提出安全性改进的量子协议设计，并证明任何量子协议均存在常数下界，同时引入作弊优势概念以量化非对称作弊场景下的安全性。
Privacy is a major concern in designing any cryptographic primitive when frequent transactions are done electronically. During electronic transactions, people reveal their personal data into several servers and believe that this information does not leak too much about them. The adaptive oblivious transfer with hidden access policy (AOT-HAP) takes measure against such privacy issues. The existing AOT-HAP involves a sender and multiple receivers apart from a designated issuer. Security of these schemes rely on the fact that the issuer cannot collude with a set of receivers. Moreover, they loose…
A Protocol for Compliant, Obliviously Managed Electronic Transfers
该研究提出了一种安全创建和转移数字资产的协议，通过引入去关联机制、盲交易机制和防止服务提供者篡改的机制，保障初始所有者的隐私和自我保管权益。
Oblivious transfer (OT) is an important tool in cryptography. It serves as a subroutine to other complex procedures of both theoretical and practical significance. Common attribute of OT protocols is that one party (Alice) has to send a message to another party (Bob) and has to stay oblivious on whether Bob did receive the message. Specific (OT) protocols vary by exact definition of the task - in the all-or-nothing protocol Alice sends a single bit-string message, which Bob is able to read only with 50% probability, whereas in 1-out-of-2 OT protocol Bob reads one out of two messages sent by Al…
A Practical Protocol for Quantum Oblivious Transfer from One-Way Functions
提出一种基于单向函数的量子不经意传输协议，在普通模型中实现模拟安全性，并通过改进效率和提供错误校正分析，促进实验实现。
We present an oblivious transfer scheme that extends the proposal made by Barreto, Oliveira and Benits, based in isogenies supersingular elliptic curves, to the setting of principally polarized supersingular abelian surfaces.
This paper has been withdrawn.
MiniQCrypt is a world where quantum-secure one-way functions exist, and quantum communication is possible. We construct an oblivious transfer (OT) protocol in MiniQCrypt that achieves simulation-security in the plain model against malicious quantum polynomial-time adversaries, building on the foundational work of Bennett, Brassard, Crépeau and Skubiszewska (CRYPTO 1991). Combining the OT protocol with prior works, we obtain secure two-party and multi-party computation protocols also in MiniQCrypt. This is in contrast to the classical world, where it is widely believed that one-way functions al…
The bounded storage model restricts the memory of an adversary in a cryptographic protocol, rather than restricting its computational power, making information theoretically secure protocols feasible. We present the first protocols for commitment and oblivious transfer in the bounded storage model with errors, i.e., the model where the public random sources available to the two parties are not exactly the same, but instead are only required to have a small Hamming distance between themselves. Commitment and oblivious transfer protocols were known previously only for the error-free variant of t…
We propose protocols for obliviously evaluating finite-state machines, i.e., the evaluation is shared between the provider of the finite-state machine and the provider of the input string in such a manner that neither party learns the other's input, and the states being visited are hidden from both. For alphabet size $|Σ|$, number of states $|Q|$, and input length $n$, previous solutions have either required a number of rounds linear in $n$ or communication $Ω(n|Σ||Q|\log|Q|)$. Our solutions require 2 rounds with communication $O(n(|Σ|+|Q|\log|Q|))$. We present two different solutions to this …
Oblivious Transfer (OT) is a major primitive for secure multiparty computation. Indeed, combined with symmetric primitives along with garbled circuits, it allows any secure function evaluation between two parties. In this paper, we propose a new approach to build OT protocols. Interestingly, our new paradigm features a security analysis in the Universal Composability (UC) framework and may be instantiated from post-quantum primitives. In order to do so, we define a new primitive named Smooth Projective Hash Function with Grey Zone (SPHFwGZ) which can be seen as a relaxation of the classical Sm…
Oblivious transfer is a powerful cryptographic primitive that is complete for secure multi-party computation. In oblivious transfer protocols a user sends one or more messages to a receiver, while the sender remains oblivious as to which messages have been received. Protocols for oblivious transfer cannot exist in a classical or fully-quantum world, but can be implemented by restricting the users' power. The isolated qubits model is a cryptographic model in which users are restricted to single-qubit operations and are not allowed to use entangling operations. Furthermore, all parties are allow…
We study the cryptographic primitive Oblivious Transfer; a composable construction of this resource would allow arbitrary multi-party computation to be carried out in a secure way, i.e. to compute functions in a distributed way while keeping inputs from different parties private. First we review a framework that allows us to analyze composability of classical and quantum cryptographic protocols in special relativity: Abstract Cryptography implemented with Causal Boxes. We then (1) explore and formalize different versions of oblivious transfer found in the literature, (2) prove that their equiv…
We present a framework for fully-simulatable $h$-out-of-$n$ oblivious transfer ($OT^{n}_{h}$) with security against non-adaptive malicious adversaries. The framework costs six communication rounds and costs at most $40n$ public-key operations in computational overhead. Compared with the known protocols for fully-simulatable oblivious transfer that works in the plain mode (where there is no trusted common reference string available) and proven to be secure under standard model (where there is no random oracle available), the instantiation based on the decisional Diffie-Hellman assumption of the…
The oblivious transfer primitive is sufficient to implement secure multiparty computation. However, secure multiparty computation based only on classical cryptography is severely limited by the security and efficiency of the oblivious transfer implementation. We present a method to efficiently and securely generate and distribute oblivious keys by exchanging qubits and by performing commitments using classical hash functions. With the presented hybrid approach, quantum and classical, we obtain a practical and high-speed oblivious transfer protocol, secure even against quantum computer attacks.…
We present a device independently secure quantum scheme for p-threshold all-or-nothing oblivious transfer. Novelty of the scheme is that, its security does not depend -- unlike the usual case -- on any quantum bit commitment protocol, rather it depends on Hardy's argument for two-qubit system. This scheme is shown to be unconditionally secure against any strategy allowed by quantum mechanics. By providing a secure scheme for all-or-nothing quantum oblivious transfer, we have answered a long standing open problem, other than the quantum key distribution, whether there is any two-party quantum c…
Two-Server Oblivious Transfer for Quantum Messages
针对现有双服务器不经意传输仅支持经典消息的局限，本文提出可处理量子消息的双服务器不经意传输协议，以支持量子网络中的量子信息处理。
Oblivious Transfer from Zero-Knowledge Proofs, or How to Achieve Round-Optimal Quantum Oblivious Transfer and Zero-Knowledge Proofs on Quantum States
本文提出了一种将经典零知识证明转换为量子隐含转移协议的通用方法，实现了最优轮次的量子隐含转移，并引入了新的复杂度类ZKstatesQIP和ZKstatesQMA。
We propose an information theoretic framework for the secure two-party function computation (SFC) problem and introduce the notion of SFC capacity. We study and extend string oblivious transfer (OT) to sample-wise OT. We propose an efficient, perfectly private OT protocol utilizing the binary erasure channel or source. We also propose the bootstrap string OT protocol which provides disjoint (weakened) privacy while achieving a multiplicative increase in rate, thus trading off security for rate. Finally, leveraging our OT protocol, we construct a protocol for SFC and establish a general lower b…
We introduce AOT, an anonymous communication system based on mix network architecture that uses oblivious transfer (OT) to deliver messages. Using OT to deliver messages helps AOT resist blending ($n-1$) attacks and helps AOT preserve receiver anonymity, even if a covert adversary controls all nodes in AOT. AOT comprises three levels of nodes, where nodes at each level perform a different function and can scale horizontally. The sender encrypts their payload and a tag, derived from a secret shared between the sender and receiver, with the public key of a Level-2 node and sends them to a Level-…
We consider oblivious transfer protocols performed over binary symmetric channels in a malicious setting where parties will actively cheat if they can. We provide constructions purely based on coding theory that achieve an explicit positive rate, the essential ingredient being the existence of linear codes whose Schur products are asymptotically good.
Delegated-Query Oblivious Transfer and its Practical Applications
针对现有不经意传输（OT）研究忽视实际应用需求的问题，提出二选一委托查询OT、多接收方委托查询OT及瘦客户端OT编译器，拓展OT在数据库隐私保护等场景的实用性。
Fuzzy Private Set Union via Oblivious Key Homomorphic Encryption Retrieval
本文提出基于 oblivious key homomorphic encryption retrieval 的模糊私有集合联合协议，通过改进的加密技术实现高效的数据联合计算。
Oblivious Quantum Computation and Delegated Multiparty Quantum Computation
提出不经意量子计算概念，利用量子隐形传态设计双服务器协议，指数级改进通信复杂度，并扩展至委托多方量子计算场景。
A boardroom election is an election with a small number of voters carried out with public communications. We present BVOT, a self-tallying boardroom voting protocol with ballot secrecy, fairness (no tally information is available before the polls close), and dispute-freeness (voters can observe that all voters correctly followed the protocol). BVOT works by using a multiparty threshold homomorphic encryption system in which each candidate is associated with a masked unique prime. Each voter engages in an oblivious transfer with an untrusted distributor: the voter selects the index of a prime a…
I-(OT)^2: A Client-optimal Oblivious Transfer Protocol for IoT Devices
针对物联网设备等客户端计算受限场景，提出一种基于二次剩余问题的1-out-of-2不经意传输协议，通过轻量级离线预计算将在线计算负担几乎全部转移给发送方，显著降低接收方计算和通信开销。
Oblivious transfer is a fundamental cryptographic primitive in which Bob transfers one of two bits to Alice in such a way that Bob cannot know which of the two bits Alice has learned. We present an optimal security bound for quantum oblivious transfer protocols under a natural and demanding definition of what it means for Alice to cheat. Our lower bound is a smooth tradeoff between the probability B with which Bob can guess Alice's bit choice and the probability A with which Alice can guess both of Bob's bits given that she learns one of the bits with certainty. We prove that 2B + A is greater…
In the m-out-of-n oblivious transfer (OT) model, one party Alice sends n bits to another party Bob, Bob can get only m bits from the n bits. However, Alice cannot know which m bits Bob received. Y.Mu[MJV02]} and Naor[Naor01] presented classical m-out-of-n oblivious transfer based on discrete logarithm. As the work of Shor [Shor94], the discrete logarithm can be solved in polynomial time by quantum computers, so such OTs are unsafe to the quantum computer. In this paper, we construct a quantum m-out-of-n OT (QOT) scheme based on the transmission of polarized light and show that the scheme is ro…
Network Oblivious Transfer via Noisy Channels: Limits and Capacities
本文研究了通过噪声信道进行 oblivion 转移的信息论极限，并提出了一种多方协议以应对诚实但好奇的参与者和潜在恶意接收方的情况。
Oblivious transfer protocol is a basic building block in cryptography and is used to transfer information from a sender to a receiver in such a way that, at the end of the protocol, the sender does not know if the receiver got the message or not. Since Shor's quantum algorithm appeared, the security of most of classical cryptographic schemes has been compromised, as they rely on the fact that factoring is unfeasible. To overcome this, quantum mechanics has been used intensively in the past decades, and alternatives resistant to quantum attacks have been developed in order to fulfill the (poten…
Oblivious RAM (ORAM) protocols are powerful techniques that hide a client's data as well as access patterns from untrusted service providers. We present an oblivious cloud storage system, ObliviSync, that specifically targets one of the most widely-used personal cloud storage paradigms: synchronization and backup services, popular examples of which are Dropbox, iCloud Drive, and Google Drive. This setting provides a unique opportunity because the above privacy properties can be achieved with a simpler form of ORAM called write-only ORAM, which allows for dramatically increased efficiency compa…
In many Internet of Things (IoT) applications, data sensed by an IoT device are continuously sent to the server and monitored against a specification. Since the data often contain sensitive information, and the monitored specification is usually proprietary, both must be kept private from the other end. We propose a protocol to conduct oblivious online monitoring -- online monitoring conducted without revealing the private information of each party to the other -- against a safety LTL specification. In our protocol, we first convert a safety LTL formula into a DFA and conduct online monitoring…
We consider oblivious transfer between Alice and Bob in the presence of an eavesdropper Eve when there is a broadcast channel from Alice to Bob and Eve. In addition to the secrecy constraints of Alice and Bob, Eve should not learn the private data of Alice and Bob. When the broadcast channel consists of two independent binary erasure channels, we derive the oblivious transfer capacity for both 2-privacy (where the eavesdropper may collude with either party) and 1-privacy (where there are no collusions).
Oblivious Monitoring for Discrete-Time STL via Fully Homomorphic Encryption
本文提出一种结合CKKS与TFHE全同态加密的协议，实现对离散时间实值信号的STL公式不经意在线监测，并通过血糖与车辆安全案例验证其实际可行性。
We derive a new upper bound on the string oblivious transfer capacity of discrete memoryless channels. The main tool we use is the tension region of a pair of random variables introduced in Prabhakaran and Prabhakaran (2014) where it was used to derive upper bounds on rates of secure sampling in the source model. In this paper, we consider secure computation of string oblivious transfer in the channel model. Our bound is based on a monotonicity property of the tension region in the channel model. We show that our bound strictly improves upon the upper bound of Ahlswede and Csiszár (2013).
We present a simplified framework for proving sequential composability in the quantum setting. In particular, we give a new, simulation-based, definition for security in the bounded-quantum-storage model, and show that this definition allows for sequential composition of protocols. Damgard et al. (FOCS '05, CRYPTO '07) showed how to securely implement bit commitment and oblivious transfer in the bounded-quantum-storage model, where the adversary is only allowed to store a limited number of qubits. However, their security definitions did only apply to the standalone setting, and it was not clea…
We study oblivious transfer (OT) between Alice and Bob in the presence of an eavesdropper Eve over a degraded wiretapped binary erasure channel from Alice to Bob and Eve. In addition to the privacy goals of oblivious transfer between Alice and Bob, we require privacy of Alice and Bob's private data from Eve. In previous work we derived the OT capacity (in the honest-but-curious model) of the wiretapped binary independent erasure channel where the erasure processes of Bob and Eve are independent. Here we derive a lower bound on the OT capacity in the same secrecy model when the wiretapped binar…
Quantum private query (QPQ) is a kind of quantum protocols to protect both users' privacy in their communication. There is an interesting example, that is, Alice wants to buy one item from Bob's database, which is composed of a quantity of valuable messages. QPQ protocol is the communication procedure ensuring that Alice can get only one item from Bob, and at the same time, Bob cannot know which one was taken by Alice. Owing to its practicability, quantum-key-distribution-based QPQ has draw much attention in recent years. However, the post-processing of the key in such protocols, called oblivi…
Oblivious Transfer (OT) is a fundamental cryptographic protocol that finds a number of applications, in particular, as an essential building block for two-party and multi-party computation. We construct a round-optimal (2 rounds) universally composable (UC) protocol for oblivious transfer secure against active adaptive adversaries from any OW-CPA secure public-key encryption scheme with certain properties in the random oracle model (ROM). In terms of computation, our protocol only requires the generation of a public/secret-key pair, two encryption operations and one decryption operation, apart…
Experimental Secure Multiparty Computation from Quantum Oblivious Transfer with Bit Commitment
本文实验实现了基于比特承诺的量子不经意传输协议，并首次将其应用于私有集合交集，证明了两家银行可在不泄露其他数据的情况下识别共同可疑账户，展示了其实际商业价值。
On (Im)possibility of Network Oblivious Transfer via Noisy Channels and Non-Signaling Correlations
研究证明通过噪声通道和非信号相关性实现完美网络盲目传输是不可能的，且即使微小泄露也无法实现，但接收方隐私不受此限制。
We propose one of the very few constructive consequences of the second law of thermodynamics. More specifically, we present protocols for secret-key establishment and multiparty computation the security of which is based fundamentally on Landauer's principle. The latter states that the erasure cost of each bit of information is at least kTln2 (where k is Boltzmann's constant and T is the absolute temperature of the environment). Albeit impractical, our protocols explore the limits of reversible computation, and the only assumption about the adversary is her inability to access a quantity of fr…
Privacy-preserving federated learning enables a population of distributed clients to jointly learn a shared model while keeping client training data private, even from an untrusted server. Prior works do not provide efficient solutions that protect against collusion attacks in which parties collaborate to expose an honest client's model parameters. We present an efficient mechanism based on oblivious distributed differential privacy that is the first to protect against such client collusion, including the "Sybil" attack in which a server preferentially selects compromised devices or simulates …
We present a simple and practical quantum protocol involving two mistrustful agencies in Minkowski space, which allows Alice to transfer data to Bob at a spacetime location that neither can predict in advance. The location depends on both Alice's and Bob's actions. The protocol guarantees unconditionally to Alice that Bob learns the data at a randomly determined location; it guarantees to Bob that Alice will not learn the transfer location even after the protocol is complete. The task implemented, transferring data at a space-time location that remains hidden from the transferrer, has no preci…
Fully Oblivious Differential Privacy for Frequency Estimation in the Augmented Shuffle Model with Trusted Processors
针对混洗模型中混洗器与数据收集者共谋的信任问题，引入可信执行环境（TEE）并定义全遗忘差分隐私（FODP），提出基于内存大小混淆的通用框架及三种具体算法，利用计数最小草图优化效率，在Intel SGX上验证有效性。
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