Oblivious transfer is such a strong cryptographic tool that it is directly used both in private data retrieval techniques and secure, multi-party computation paradigms. We propose an optimal oblivious transfer, where the communication complexity is logarithmic in size of the database with minimum computation overhead - the computational complexity in any oblivious transfer protocol is at least linear in the size of the database. Our communication-efficient oblivious transfer protocol is a non-interactive, single-database scheme that is generally based on homomorphic encryption functions.
Oblivious transfer is such a strong cryptographic tool that it is directly used both in private data retrieval techniques and secure, multi-party computation paradigms. We propose an optimal oblivious transfer, where the communication complexity is logarithmic in size of the database with minimum computation overhead - the computational complexity in any oblivious transfer protocol is at least linear in the size of the database. Our communication-efficient oblivious transfer protocol is a non-interactive, single-database scheme that is generally based on homomorphic encryption functions.
Abstract. We propose a one-round 1-out-of-n computationally-private information retrieval protocol for ℓ-bit strings with low-degree polylogarithmic receivercomputation, linear sender-computation and communication Θ(k · log 2 n + ℓ · log n), where k is a possibly non-constant security parameter. The new protocol is receiver-private if the underlying length-flexible additively homomorphic public-key cryptosystem is IND-CPA secure. It can be transformed to a one-round computationally receiver-private and information-theoretically sender-private 1out-of-n oblivious-transfer protocol for ℓ-bit strings, that has the same asymptotic communication and is private in the standard complexity-theoretic model. Keywords. Computationally-private information retrieval, length-flexible additively homomorphic public-key cryptosystem, oblivious transfer. 1
We present an unconditionally secure Oblivious Transfer protocol relying on two rounds of entanglement-free quantum communication. When played honestly, the protocol only requires the ability to measure a single qubit in a fixed basis, and to perform a coherent bit-flip (Pauli X) operation. We present a generalization to a "Private Data Sampling" protocol, where a player (Bob) can obtain a random sample of fixed size from a classical database of size N, while the database owner (Alice) remains oblivious as to which bits were accessed. The protocol is efficient in the sense that the communication complexity per query scales at most linearly with the size of the database. It does not violate Lo's "no-go" theorem for one-sided two-party secure computation, since a given joint input by Alice and Bob can result in randomly different protocol outcomes. Finally it could be used to implement a practical bit string commitment protocol, among other applications.
In this paper, we present a new application for , n 1 oblivious transfer, which i s a n i n teractive protocol between two parties Alice and Bob, where Alice has n secrets and Bob has a query i.A t the end of the protocol Bob has the ith secret and no other information about Alice's other secrets, while Alice does not get any information about i.This new application is the Secure Database Access problem.Motivated by this application, we propose an OT scheme which a c hieves low communication complexity and information theoretic security.We use a distributed model for , n 1 oblivious transfer, where Bob interacts with multiple \Alices".In this model, we base our scheme on any PIR scheme, which i s a s c heme where only the privacy of Bob is considered, and use it to construct an OT scheme, private for both parties, without paying too much i n communication complexity.This results in the rst sublinear information theoretic scheme for , n 1 OT.Further motivated by the application of , n 1 OT for polynomial n, w e raise the issue of repetition in , n 1 OT, where both security and eciency are important.We show that previous protocols for , n 1 oblivious transfer fail in this setting.
Oblivious transfer is one of the most important cryptographic primitives, both for theoretical and practical reasons and several protocols were proposed during the years. We provide the first oblivious transfer protocol which is simultaneously optimal on the following list of parameters: Security: it has universal composition. Trust in setup assumptions: only one of the parties needs to trust the setup (and some setup is needed for UC security). Trust in computational assumptions: only one of the parties needs to trust a computational assumption. Round complexity: it uses only two rounds. Communication complexity: it communicates O(1) group elements to transfer one out of two group elements. The Big-O notation hides 32, meaning that the communication is probably not optimal, but is essentially optimal in that the overhead is at least constant. Our construction is based on pairings, and we assume the presence of a key registration authority.
Oblivious Transfer (OT) is an important cryptographic tool, which has found its usage in many crypto protocols, such as Secure Multiparty Computations [9], Certified E-mail [2] and Simultaneous Contract Signing [20].In this paper, we propose three k-out-of-n OT (OT n k ) protocols based on additive homomorphic encryption.Two of these protocols prohibit malicious behaviors from both sender and receiver.We also achieve efficient communication complexity bounded by O(l • n) in bits, where l is the size of the encryption key.The computational complexity is same or better than the most efficient existing protocols.Due to the semantic security property, the sender cannot get receiver's selection.When the receiver tries to retrieve more than k values, the receiver is caught cheating with 1 -1/m probability (Protocol II) or the receiver is unable to get any value at all (Protocol III).We introduce a novel technique based on the solvability of linear equations, which could find its way into other applications.We also provide an experimental analysis to compare the efficiency of the protocols.
In this work we consider the following primitive, that we call restricted adaptive oblivious transfer. On the one hand, the owner of a database wants to restrict the access of users to this data according to some policy, in such a way that a user can only obtain information satisfying the restrictions imposed by the owner. On the other hand, a legitimate user wants to privately retrieve allowed parts of the data, in a sequential and adaptive way, without letting the owner know which part of the data is being obtained. After having formally described the components and required properties of a protocol for restricted adaptive oblivious transfer, we propose two schemes to realize this primitive. The first one is only of theoretical interest at the current time, because it uses a cryptographic tool which has not been realized yet: cryptosystems which are both multiplicatively and additively homomorphic. The second scheme, fully implementable, is based on secret sharing schemes.