A Novel Multi-factor ID-based Designated Verifier Signature scheme

In a classic digital signature scheme, the global community is capable of verifying a signature. In a designated verifier scheme (DVS), only the designated verifier has this capability. In a classic DVS scheme the signer themselves ``designates\u27\u27 the entity that will have the capability of verifying their signature. In a pure identity-based signature scheme a Trusted Authority is introduced, and is responsible for issuing secret signing keys to all participants. In our proposed scheme it is this TA, not the signer, that designates the verifier, and to this end the TA issues the designated verifier with its own secret. Finally we propose a variation that supports non-repudiation, plus a hardware-free multi-factor signature capability

Efficient and Provably-secure Certificateless Strong Designated Verifier Signature Scheme without Pairings

Strong designated verifier signature (generally abbreviated to SDVS) allows signers to obtain absolute control over who can verify the signature, while only the designated verifier other than anyone else can verify the validity of a SDVS without being able to transfer the conviction. Certificateless PKC has unique advantages comparing with certificate-based cryptosystems and identity-based PKC, without suffering from key escrow. Motivated by these attractive features, we propose a novel efficient CL-SDVS scheme without bilinear pairings or map-to-point hash operations. The proposed scheme achieves all the required security properties including EUF-CMA, non-transferability, strongness and non-delegatability. We also estimate the computational and communication efficiency. The comparison shows that our scheme outperforms all the previous CL-(S)DVS schemes. Furthermore, the crucial security properties of the CL-SDVS scheme are formally proved based on the intractability of SCDH and ECDL assumptions in random oracle model

An Efficient Certificate-Based Designated Verifier Signature Scheme

Certificate-based public key cryptography not only solves certificate revocation problem in traditional PKI but also overcomes key escrow problem inherent in identity-based cryptosystems. This new primitive has become an attractive cryptographic paradigm. In this paper, we propose the notion and the security model of certificate-based designated verifier signatures (CBDVS). We provide the first construction of CBDVS and prove that our scheme is existentially unforgeable against adaptive chosen message attacks in the random oracle model. Our scheme only needs two pairing operations, and the signature is only one element in the bilinear group G1. To the best of our knowledge, our scheme enjoys shortest signature length with less operation cost

On the Security of a Novel Probabilistic Signature Based on Bilinear Square Diffie-Hellman Problem and Its Extension

Probabilistic signature scheme has been widely used in modern electronic commerce since it could provide integrity, authenticity, and nonrepudiation. Recently, Wu and Lin proposed a novel probabilistic signature (PS) scheme using the bilinear square Diffie-Hellman (BSDH) problem. They also extended it to a universal designated verifier signature (UDVS) scheme. In this paper, we analyze the security of Wu et al.’s PS scheme and UDVS scheme. Through concrete attacks, we demonstrate both of their schemes are not unforgeable. The security analysis shows that their schemes are not suitable for practical applications

IoT-REX: A Secure Remote-Control System for IoT Devices from Centralized Multi-Designated Verifier Signatures

IoT technology has been developing rapidly, while at the same time, notorious IoT malware such as Mirai is a severe and inherent threat. We believe it is essential to consider systems that enable us to remotely control infected devices in order to prevent or limit malicious behaviors of infected devices. In this paper, we design a promising candidate for such remote-control systems, called IoT-REX (REmote-Control System for IoT devices). IoT-REX allows a systems manager to designate an arbitrary subset of all IoT devices in the system and every device can confirm whether or not the device itself was designated; if so, the device executes a command given from the systems manager. Towards realizing IoT-REX, we introduce a novel cryptographic primitive called centralized multi-designated verifier signatures (CMDVS). Although CMDVS works under a restricted condition compared to conventional MDVS, it is sufficient for realizing IoT-REX. We provide an efficient CMDVS construction from any approximate membership query structures and digital signatures, yielding compact communication sizes and efficient verification procedures for IoT-REX. We then discuss the feasibility of IoT-REX through cryptographic implementation of the CMDVS construction on a Raspberry Pi. Our promising results demonstrate that the CMDVS construction can compress communication size to about 30% and thus its resulting IoT-REX becomes three times faster than a trivial construction over typical low-power wide area networks with an IoT device. It is expected that IoT-REX can control 12,000 devices within a second.Comment: Updated as a whole. 26 page

Development of Time-Stamped Signcryption Scheme and its Application in E-Cash System

A signcryption scheme combining public key encryptions and digital signatures in one logical step can simultaneously satisfy the security requirements of confidentiality, integrity, authenticity and non-repudiation and with a cost significantly lower than that required by the traditional "signature followed by encryption" approach. This thesis presents a new generic concept of time-stamped signcryption scheme with designated verifiability. Here an authenticated time-stamp is associated with the signcrypted text which can only be verifiable by a specific person, known as the designated verifier. The time-stamp is provided by a trusted third party, namely, Time Stamping System (TSS). The scheme is proved to be secure, as, no one, not even the signcrypter or TSS can produce a valid signcrypted text on behalf of them. We analyzed the security of the proposed scheme and found that it can withstand some active attacks. This scheme is resistant against both inside and outside attacks. The security of our scheme is based upon the hardness of solving Computational Diffie Hellman Problem (CDH), Discrete Logarithm Problem (DLP) and Integer Factorization Problem (IFP). The proposed scheme is suitable in scenarios such as, on-line patent submission, on-line lottery, e-cash, e-bidding and other e-commerce applications. Also we propose an e-cash system based on our proposed time-stamped signcryption scheme which confirms the notion of e-cash securities like anonymity of the spender, unforgeablity of the digital coin, prevention of double spending

Bringing data minimization to digital wallets at scale with general-purpose zero-knowledge proofs

Today, digital identity management for individuals is either inconvenient and error-prone or creates undesirable lock-in effects and violates privacy and security expectations. These shortcomings inhibit the digital transformation in general and seem particularly concerning in the context of novel applications such as access control for decentralized autonomous organizations and identification in the Metaverse. Decentralized or self-sovereign identity (SSI) aims to offer a solution to this dilemma by empowering individuals to manage their digital identity through machine-verifiable attestations stored in a "digital wallet" application on their edge devices. However, when presented to a relying party, these attestations typically reveal more attributes than required and allow tracking end users' activities. Several academic works and practical solutions exist to reduce or avoid such excessive information disclosure, from simple selective disclosure to data-minimizing anonymous credentials based on zero-knowledge proofs (ZKPs). We first demonstrate that the SSI solutions that are currently built with anonymous credentials still lack essential features such as scalable revocation, certificate chaining, and integration with secure elements. We then argue that general-purpose ZKPs in the form of zk-SNARKs can appropriately address these pressing challenges. We describe our implementation and conduct performance tests on different edge devices to illustrate that the performance of zk-SNARK-based anonymous credentials is already practical. We also discuss further advantages that general-purpose ZKPs can easily provide for digital wallets, for instance, to create "designated verifier presentations" that facilitate new design options for digital identity infrastructures that previously were not accessible because of the threat of man-in-the-middle attacks

Strong Designated Verifier Signature Schemes with Undeniable Property and Their Applications

Most of the strong designated verifier signature (SDVS) schemes cannot tell the real signature generator when the signer and the designated verifier dispute on a signature. In other words, most of the SDVS schemes do not have the undeniability property. In this paper, we propose two SDVS schemes which hold the undeniability property, namely, strong designated verifier signature with undeniability property (SDVSUP). Our two schemes are called SDVSUP-1 and SDVSUP-2. In our two SDVSUP schemes, the signer not only can designate a verifier but also can designate an arbiter who can judge the signature when the signer and the designated verifier dispute on the signature. What is more, the judgment procedure can be performed by the arbiter alone without help from the signer or the designated verifier, which increases the judgment efficiency and reduces the complexity of signature confirmation. We also demonstrate a real instance of applying our SDVSUP scheme to electronic bidding system