Verifiable secret sharing

About: Verifiable secret sharing is a research topic. Over the lifetime, 4241 publications have been published within this topic receiving 99569 citations.

Verifiable Timed Signatures Made Practical

Abstract: A verifiable timed signature (VTS) scheme allows one to time-lock a signature on a known message for a given amount of time T such that after performing a sequential computation for time T anyone can extract the signature from the time-lock. Verifiability ensures that anyone can publicly check if a time-lock contains a valid signature on the message without solving it first, and that the signature can be obtained by solving the same for time T. This work formalizes VTS, presents efficient constructions compatible with BLS, Schnorr, and ECDSA signatures, and experimentally demonstrates that these constructions can be employed in practice. On a technical level, we design an efficient cut-and-choose protocol based on the homomorphic time-lock puzzles to prove the validity of a signature encapsulated in a time-lock puzzle. We also present a new efficient range proof protocol that significantly improves upon existing proposals in terms of the proof size, and is also of independent interest. While VTS is a versatile tool with numerous existing applications, we demonstrate VTS's applicability to resolve three novel challenging issues in the space of cryptocurrencies. Specifically,we show how VTS is the cryptographic cornerstone to construct:(i) Payment channel networks with improved on-chain unlinkability of users involved in a transaction, (ii) multi-party signing of transactions for cryptocurrencies without any on-chain notion oftime and (iii) cryptocurrency-enabled fair multi-party computation protocol.

Verifiable Delegated Set Intersection Operations on Outsourced Encrypted Data.

Abstract: We initiate the study of the following problem: Suppose Alice and Bob would like to outsource their encrypted private data sets to the cloud, and they also want to conduct the set intersection operation on their plaintext data sets. The straightforward solution for them is to download their outsourced cipher texts, decrypt the cipher texts locally, and then execute a commodity two-party set intersection protocol. Unfortunately, this solution is not practical. We therefore motivate and introduce the novel notion of Verifiable Delegated Set Intersection on outsourced encrypted data (VDSI). The basic idea is to delegate the set intersection operation to the cloud, while (i) not giving the decryption capability to the cloud, and (ii) being able to hold the misbehaving cloud accountable. We formalize security properties of VDSI and present a construction. In our solution, the computational and communication costs on the users are linear to the size of the intersection set, meaning that the efficiency is optimal up to a constant factor.

Oblivious Pseudorandom Functions from Isogenies

Abstract: An oblivious PRF, or OPRF, is a protocol between a client and a server, where the server has a key k for a secure pseudorandom function F, and the client has an input x for the function. At the end of the protocol the client learns F(k, x), and nothing else, and the server learns nothing. An OPRF is verifiable if the client is convinced that the server has evaluated the PRF correctly with respect to a prior commitment to k. OPRFs and verifiable OPRFs have numerous applications, such as private-set-intersection protocols, password-based key-exchange protocols, and defense against denial-of-service attacks. Existing OPRF constructions use RSA-, Diffie-Hellman-, and lattice-type assumptions. The first two are not post-quantum secure.

A publicly verifiable lossless watermarking scheme for copyright protection and ownership assertion

Abstract: In this paper, a discrete cosine transform based copyright protection scheme that does not require the original image for logo verification is proposed. Features of logistic map and discrete cosine transform are used to generate the verification map. Digital signature and timestamp are used to make copyright proving publicly verifiable. We have combined cryptographic tools and digital watermarking, in order to enhance the security and reliability of copyright protection. In addition, chaotic map is used to generate a chaotic pattern image, which can be used as secret key to improve the security of proposed algorithm. Experiments are conducted to show the robustness and effectiveness of the proposed algorithm. Experimental results show that our scheme outperforms related works in most of the cases.

A Light-weight and Attack-Proof Bidirectional Blockchain Paradigm for Internet of Things

Abstract: Diverse technologies, such as machine learning and big data, have been driving the prosperity of the Internet of Things (IoT) and the ubiquitous proliferation of IoT devices. Consequently, it is natural that IoT becomes the driving force to meet the increasing demand for frictionless transactions. To secure transactions in IoT, blockchain is widely deployed since it can remove the necessity of a trusted central authority. However, the mainstream blockchain-based IoT payment platforms, dominated by Proof-of-Work (PoW) and Proof-of-Stake (PoS) consensus algorithms, face several major security and scalability challenges that result in system failures and financial loss. Among the three leading attacks in this scenario, double-spend attacks and long-range attacks threaten the tokens of blockchain users, while eclipse attacks target denial of service. To defeat these attacks, a novel bidirectional-linked blockchain (BLB) using chameleon hash functions is proposed, where bidirectional pointers are constructed between blocks. Furthermore, a new Committee Members Auction (CMA) consensus algorithm is designed to improve the security and attack resistance of BLB while guaranteeing high scalability. In CMA, distributed blockchain nodes elect committee members through a verifiable random function. The smart contract uses Shamir’s Secret Sharing scheme to distribute the trapdoor keys to committee members. To better investigate BLB’s resistance against double-spend attacks, an improved Nakamoto’s attack analysis is presented. In addition, a modified entropy metric is devised to measure eclipse attack resistance across different consensus algorithms. Extensive evaluation results show the superior resistance against attacks and demonstrate high scalability of BLB compared with current leading paradigms based on PoS and PoW.