Abstract. Membership encryption is a newly developed cryptographic primitive that combines membership proof and encryption into an unified setting. This paper presents a new flexible mem-bership encryption scheme which is provably secure and significantly more efficient than the previous scheme. Further we apply our proposed membership encryption to construct a round optimal 1-out-of-n priced oblivious transfer (POT) protocol which, unlike the existing 1-out-of-n POT schemes, is proven secure under the universally composable (UC) security model and thus preserves secu-rity when it is executed with multiple protocol instances that run concurrently in an adversarily controlled way. Moreover, using our membership encryption, the POT protocol exhibits constant communication complexity on the buyer’s side and O(n) communication cost on the vendor’s side, which is so far the best known in the literature.
Abstract. Membership encryption is a newly developed cryptographic primitive that combines membership proof and encryption into an unified setting. This paper presents a new flexible mem-bership encryption scheme which is provably secure and significantly more efficient than the previous scheme. Further we apply our proposed membership encryption to construct a round optimal 1-out-of-n priced oblivious transfer (POT) protocol which, unlike the existing 1-out-of-n POT schemes, is proven secure under the universally composable (UC) security model and thus preserves secu-rity when it is executed with multiple protocol instances that run concurrently in an adversarily controlled way. Moreover, using our membership encryption, the POT protocol exhibits constant communication complexity on the buyer’s side and O(n) communication cost on the vendor’s side, which is so far the best known in the literature.
Non-committing encryption achieved only semantic security,in contrast,applications often require security against chosen ciphertext attacks.A main ingredient in the previous adaptive universally composable(UC)oblivious transfer protocols are non-committing encryptions.the previous proposals are not UC secure against adaptive adversaries in the so-called non-erase model.A new UC secure oblivious transfer protocols were proposed and schemes utilize two primitives of the verifiably smooth projective hashing and deniable encryption as constructed by.the double trapdoor decryption mechanism based on trapdoor commitment.Our construction is based on the decisional composite residuosity in common reference string (CRS) model.We constructed a two-message(1-round) string oblivious transfer protocol,which improves computational efficient that supports message spaces of size exponential and save O(n)-1 rounds communications efficient than bit-OT protocols.
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 from a few calls to the random oracle. In~terms of communication, our protocol only requires the transfer of one public-key, two ciphertexts, and three binary strings of roughly the same size as the message. Next, we show how to instantiate our construction under the low noise LPN, McEliece, QC-MDPC, LWE, and CDH assumptions. Our instantiations based on the low noise LPN, McEliece, and QC-MDPC assumptions are the first UC-secure OT protocols based on coding assumptions to achieve: 1) adaptive security, 2) optimal round complexity, 3) low communication and computational complexities. Previous results in this setting only achieved static security and used costly cut-and-choose techniques.Our instantiation based on CDH achieves adaptive security at the small cost of communicating only two more group elements as compared to the gap-DH based Simplest OT protocol of Chou and Orlandi (Latincrypt 15), which only achieves static security in the ROM.
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.
A new oblivious transfer protocol was proposed within the framework of universally composable security（UC-DT）.The protocol based on the verifiably smooth projective hashing（VSPH） is against adaptive adversaries in a common reference string（CRS） model.The UC-OT protocol improves computational efficiency with non-committing encryptions（NCE）which is based on decisional compounding residuosity,achieves UC-OT,and it saves O（n）-1 rounds in communication efficiency than bit-OT protocols.Compared with Canetti’s scheme in non-erase model,the message reduced once.Compared with Fischlin’s scheme,the message transfers were reduced twice,and the scheme does not rely on the auxiliary party,therefore it is more practical.
We present a general framework for constructing non-interactive universally composable (UC) commitment schemes that are secure against adaptive adversaries in the non-erasure setting under a single re-usable common reference string. Previously, such “fully-equipped ” UC commitment schemes are only known in [8, 9], with an unavoidable overhead of O(κ) in the sense of communication and computational complexities; meaning that to commit λ bits, the communication and computational costs require O(λκ), where κ denotes the security parameter. Efficient construction of a fully-equipped UC commitment scheme was a long-standing open problem. We introduce a cryptographic primitive, called all-but-many encryptions (ABMEs), and prove that it is a translation of fully-equipped UC commitment in the primitive level. We then construct ABMEs from cryptographic primitives that we call a probabilistic pseudo random function family and extractable sigma protocols – the former is a probabilistic version of a pseudo random function family and the latter is a special kind of sigma (i.e., canonical 3-round public-coin HVSZK) protocols with some extractability. We provide fully-equipped UC commitment schemes from ABMEs under DDH and DCR-based assumptions, respectively. In particular, the DCR-based scheme is the first fully-equipped UC commitment scheme with optimal expansion factor Ω(1); to commit κ bits, the communication and computational costs are Ω(κ). We further construct a fully-equipped UC commitment scheme from a general assumption (in which trap-door permutations exist), which is far more efficient than the previous construction [9], because, unlike [9], our construction does not require non-interactive zero-knowledge proof systems. 1
Abstract Priced oblivious transfer (POT) is a cryptographic protocol in which a merchant provides a set of items for sale and a customer acquires one of them. The protocol guarantees that the customer receives the item if and only if they have paid its price, while the merchant remains oblivious to the acquired item. Obviously, the merchant cannot not know what price the client has paid, as such price could be unique. A recent paper proposes a POT protocol that is built from two blocks: an e-coin system and an asymmetric secure computation protocol. In this paper, we present a quantum-resistant proposal for the latter building block. As a result, we are able to construct a quantum-resistant POT protocol implemented from the newly proposed asymmetric secure computation protocol and a post-quantum implementation of the mentioned e-coin system. To our knowledge, no quantum-resistant POT protocol has been proposed so far.