Multiple Signers Research Articles

Two-Round Multi-Signatures from Okamoto Signatures

Multi-signatures (MS) are a special type of public-key signature (PKS) in which multiple signers participate cooperatively to generate a signature for a single message. Recently, applications that use an MS scheme to strengthen the security of blockchain wallets or to strengthen the security of blockchain consensus protocols are attracting a lot of attention. In this paper, we propose an efficient two-round MS scheme based on Okamoto signatures rather than Schnorr signatures. To this end, we first propose a new PKS scheme by modifying the Okamoto signature scheme and prove the unforgeability of our PKS scheme under the discrete logarithm assumption in the algebraic group model (AGM) and the non-programmable random oracle model (ROM). Next, we propose a two-round MS scheme based on the new PKS scheme and prove the unforgeability of our MS scheme under the discrete logarithm assumption in the AGM and the non-programmable ROM. Our MS scheme is the first one to prove security among two-round MS based on Okamoto signatures.

A new quantum multi-party signature protocol based on SNOP states without arbitrator

As an important part of quantum signature, quantum multi-party signature solves the practical signing problem of requiring multiple signers or multiple verifiers. However, most of the existing multi-party signature protocols focus on the situation of multiple signers. Meanwhile the arbitrator is usually introduced to ensure their security. In this paper, we propose a new quantum multi-party signature protocol without arbitrator where multiple signers and multiple verifiers simultaneously appear in it. During the protocol, the strongly nonlocal orthogonal product (SNOP) states are applied to generate the signed messages. According to our analysis, it can be seen that this protocol is resistant to denial and forgery attacks, even if some of the participants collude. We hope the ideas and methods may make positive effects to the further research of quantum signature.

A survey of multi-signature schemes for XML documents

Extensible markup language (XML) is a widely used data exchange format in various fields for data transmission over the web. But due to security risk, the privacy of XML documents cannot be ensured, and hence sharing of data had become the major challenge. Web vulnerabilities cause threats to XML data confidentiality and integrity. There is a set of security mechanisms such as encryption, decryption, digital signature, and validations, which are applied to XML documents. Signing a document is the commonly used method for ensuring the authentication, non-repudiation, and integrity in which only a single signer is responsible for signing a document. But nowadays, the responsibility of signing a document is shared among multiple signers instead of a single signer which results in increasing the popularity of using multi-signature schemes. Therefore, a document may have multiple signatures and the integrity of the entire document depends upon it. This arises the need of studying various multi-signature schemes. Here, in this paper, various developments in the era of multi-signature schemes as well as its application areas are discussed.

Certificateless Broadcast Multisignature Scheme Based on MPKC

Broadcast multisignature allows multiple signers to sign the same message, which can be used in many areas, such as electronic contract signing, educational administration management system and grade management system. At present, the security of most broadcast multisignature schemes mainly depends on the intractability of large integer factoring (LIF) or discrete logarithm (DL) problem. Thus, broadcast multisignature schemes will suffer from the potential threat of the quantum computing attacks. Hence, it is an important problem how to solve the quantum computing attacks in traditional broadcast multisignature. In this paper, we construct the first certificateless broadcast multisignature scheme based on multivariate public key cryptosystem (MPKC-CLBMSS), whose security is based on the hardness of the isomorphism of polynomials (IP) problem. MPKC-CLBMSS not only solves the problem of quantum computing attacks, but also avoids the key escrow issue in IB-PKC along with the certificate management problem in traditional PKI. In MPKC-CLBMSS, the signature length is as same as that of the partial signature, regardless of the number of signers; the verification time of signature is as same as for a partial signature. MPKC-CLBMSS has higher computational efficiency than the existing broadcast multisignature scheme. Moreover, the security proof shows that MPKC-CLBMSS satisfies the unforgeability in the random oracle model.

Secure Digital Certificate-Based Data Access Control Scheme in Blockchain

Previous contract protocols in blockchains ensure their fairness and traceability by utilizing centralized credible nodes. If credible nodes are dishonest or conspire with the signatory, then other nodes are compromised. Meanwhile, the leakage of sensitive information of participant nodes poses a serious threat to the privacy security of data access in blockchains. To address this issue, this study proposes a secure control method of digital certificate-based data access in blockchains. The proposed method combines blockchain and digital certificate technologies and designs a secure authentication protocol for privacy data in blockchains without verifying the encrypted identity signature of the third-party participant. The high-efficiency network forwarding protocol proposed in this work can support the fair contract signing of multiple signers via blockchain. This protocol can protect the privacy of contracts and identities of participants. Experimental results show that the proposed scheme is superior in terms of communication overhead, storage overhead, and detection rate.

Investigating the Common Authorship of Signatures by Off-Line Automatic Signature Verification Without the Use of Reference Signatures

In automatic signature verification, questioned specimens are usually compared with reference signatures. In writer-dependent schemes, a number of reference signatures are required to build up the individual signer model while a writer-independent system requires a set of reference signatures from several signers to develop the model of the system. This paper addresses the problem of automatic signature verification when no reference signatures are available. The scenario we explore consists of a set of signatures, which could be signed by the same author or by multiple signers. As such, we discuss three methods which estimate automatically the common authorship of a set of off-line signatures. The first method develops a score similarity matrix, worked out with the assistance of duplicated signatures; the second uses a feature-distance matrix for each pair of signatures; and the last method introduces pre-classification based on the complexity of each signature. Publicly available signatures were used in the experiments, which gave encouraging results. As a baseline for the performance obtained by our approaches, we carried out a visual Turing Test where forensic and non-forensic human volunteers, carrying out the same task, performed less well than the automatic schemes.

A new batch verification scheme for ECDSA$$^*$$ signatures

In this paper, we propose an efficient batch verification algorithm for ECDSA $$^*$$ (Elliptic Curve Digital Signature Algorithm) $$^*$$ signatures. Our scheme is efficient for both single and multiple signers. ECDSA $$^*$$ signature is a modified version of ECDSA, which accelerates the verification of ECDSA signature by more than 40%. However, the highlighting feature of our proposed scheme is its efficiency for varied batch sizes. The scheme is resistant to forgery attacks by either signer or intruder. The performance of our scheme remains consistent for higher batch sizes too ( $$\ge 8$$ ). Our paper also discusses the possible attacks on ECDSA signatures and also how our scheme is resistant to such attacks.

Identity-Based Blind Multisignature From Lattices

Blind multisignature (BMS), first introduced by Horster et al , constitutes a crucial primitive that allows a user to generate a signature of a message from multiple signers, while the signers cannot obtain any information about the message. With these useful properties, blind multisignature is suitable for electronic payments and electronic voting. However, most of the current BMS schemes may be attacked by quantum computers in the future because they are based on traditional number theories, such as discrete logarithm assumption and large integer factor assumption. In this work, we first formalize the notion and the sound security models of the identity-based blind multisignature scheme (IDBMS). Then we present an instantiation based on lattices, along with rigorous proofs of the blindness and unforgeability under the lattice hard assumption (short integer solution, SIS), which is considered to remain secure under quantum computer attacks. To the best of our knowledge, it is the first identity-based quantum-resistant scheme that has the advantages of blind signature and multisignature.

Batch verification of Digital Signatures: Approaches and challenges

Digital Signatures can be considered analogous to an ordinary handwritten signature for signing messages in the Digital world. Digital signature must be unique and exclusive for each signer. Multiple Digital Signatures signed by either single or multiple signers can be verified at once through Batch Verification. There are two main issues with respect to Batch Verification of Digital Signatures; first is the security problem and the second is the computational speed. Due to e-commerce proliferation, quick verification of Digital Signatures through specific hardware or efficient software becomes critical. Internet companies, banks, and other such organizations use Batch verification to accelerate verification of large number of Digital Signatures. Many Batch Verification techniques have been proposed for various Digital Signature algorithms. But most of them lack the security requirements such as signature authenticity, integrity, and non-repudiation. Hence there is a need for the study of batch verification of Digital Signatures. The main contributions of our survey include: (a) Identifying and categorizing various Batch verification techniques for RSA, DSS, and ECDSA(includes schemes based on Bilinear Pairing) (b) Providing a comparative analysis of these Batch Verification techniques (c) Identifying various research challenges in the area of Batch verification of signatures.

Movement Epenthesis Detection for Continuous Sign Language Recognition

AbstractAutomatic sign language recognition (SLR) is a current area of research as this is meant to serve as a substitute for sign language interpreters. In this paper, we present the design of a continuous SLR system that can extract out the meaningful signs and consequently recognize them. Here, we have used height of the hand trajectory as a salient feature for separating out the meaningful signs from the movement epenthesis patterns. Further, we have incorporated a unique set of spatial and temporal features for efficient recognition of the signs encapsulated within the continuous sequence. The implementation of an efficient hand segmentation and hand tracking technique makes our system robust to complex background as well as background with multiple signers. Experiments have established that our proposed system can identify signs from a continuous sign stream with a 92.8% spotting rate.

Continuous sign language recognition: Towards large vocabulary statistical recognition systems handling multiple signers

This work presents a statistical recognition approach performing large vocabulary continuous sign language recognition across different signers. Automatic sign language recognition is currently evolving from artificial lab-generated data to ‘real-life’ data. To the best of our knowledge, this is the first time system design on a large data set with true focus on real-life applicability is thoroughly presented. Our contributions are in five areas, namely tracking, features, signer dependency, visual modelling and language modelling. We experimentally show the importance of tracking for sign language recognition with respect to the hands and facial landmarks. We further contribute by explicitly enumerating the impact of multimodal sign language features describing hand shape, hand position and movement, inter-hand-relation and detailed facial parameters, as well as temporal derivatives. In terms of visual modelling we evaluate non-gesture-models, length modelling and universal transition models. Signer-dependency is tackled with CMLLR adaptation and we further improve the recognition by employing class language models. We evaluate on two publicly available large vocabulary databases representing lab-data (SIGNUM database: 25 signers, 455 sign vocabulary, 19k sentences) and unconstrained ‘real-life’ sign language (RWTH-PHOENIX-Weather database: 9 signers, 1081 sign vocabulary, 7k sentences) and achieve up to 10.0%/16.4% and respectively up to 34.3%/53.0% word error rate for single signer/multi-signer setups. Finally, this work aims at providing a starting point to newcomers into the field.

Unconditionally Anonymous Ring and Mesh Signatures

We generalize the ring signature primitive into the more general notion of mesh signature. Ring signatures are anonymous signatures made by someone who wishes to hide in the anonymity of a larger crowd. All that the signer needs to assemble such a virtual crowd is her own private key and the public keys of the other members. The crowd composition is all that the verifier will be able to see. In a sense, a ring signature expresses an anonymous endorsement of a message by a disjunction of signers. Mesh signatures generalize this notion by allowing the combination of "atomic" (i.e., regular) signatures, by one or multiple signers from an arbitrary larger crowd, into virtually any monotone "endorsement formula" with much more expressive power than a simple disjunction. The verifier sees only that the endorsement is valid for the stated formula, not how the formula is satisfied. As a special case, mesh signatures extend the ring signature functionality to certificate chains. This is useful when the anonymity-seeking signer wishes to hide in a crowd comprising uncooperative people who do not even have a published signature verification key on record. We give an efficient linear-size construction based on bilinear maps in the common random string model. Our mesh signatures achieve everlasting perfect anonymity--an imperative for the archetypical whistle-blowing use case of ring signatures--and, as a special case, yield the first unconditionally anonymous ring signatures without random oracles or trusted setup authorities. Non-repudiation is achieved from a mild extension of the SDH assumption, named Poly-SDH, which we introduce and justify meticulously.

Lattice-Based Multi-Signature Schemes

Based on preimage sampleable functions and hard problems for lattices, we propose two lattice-based multi-signature schemes, which include the trivial broadcasting multi-signature scheme and the sequential multi-signature scheme. In the broadcasting multi-signature scheme, the length of the multi-signature varies linearly with the number of the signers. In the sequential multi-signature scheme, the length of the multi-signature is fixed and independent of the number of the signers. These two multi-signature schemes can allow multiple signers to sign the same message cooperatively.

Provably convertible multi-authenticated encryption scheme for generalized group communications

In 2008, Wu et al. proposed a convertible multi-authenticated encryption (CMAE) scheme based on discrete logarithms. To improve the computational efficiency of Wu et al.’s scheme, Tsai proposed another CMAE scheme without using message redundancy. These CMAE schemes, however, might be inadequate for group-oriented applications. In the same year, Chang presented a CMAE scheme using message redundancy for group communications [published in Information Sciences 178 (17) (2008) 3426–3434]. In his scheme, multiple signers of the same group can cooperate with each other to generate a valid authenticated encryption signature for a designated verifying group with access structured multiple verifiers. In this paper, we propose a new convertible multi-authenticated encryption scheme without using message redundancy for generalized group communications. Multiple signers of the signing group can cooperate with each other to generate a valid authenticated encryption signature for a verifying group with access structured multiple verifiers. The verifiers in the same access structure can cooperatively recover and verify the signing group’s signature. In case of a later dispute, any participant verifier can convert the authenticated encryption signature into an ordinary one. As compared with previous works, our proposed scheme is more efficient in terms of computational efforts and communication overheads.

When and Why Individuals Obey Form-Adhesive Contracts: Experimental Evidence of Consent, Compliance, Promise, and Performance

When and Why Individuals Obey Form-Adhesive Contracts: Experimental Evidence of Consent, Compliance, Promise, and Performance, 10.1628/093245612799440078, Jahrgang 168 (2012) / Heft 1, 0932-4569 (1614-0559)

Attacking M&M Collective Signature Scheme

A collective signature scheme aims to solve the problem of signing a message by multiple signers. Recently, Moldovyan and Moldovyan proposed a scheme for collective signatures based on Schnorr signatures. We show some security weaknesses of the scheme.

Encryption scheme for weighted threshold authentication

A convertible authenticated encryption(CAE) scheme allows designated recipients to simultaneously recover and verify the message,while a convertible multi-authenticated encryption(CAME) scheme allows a signing group with multiple signers to generate a multi-authenticated signature-ciphertext on the chosen message.Motivated by the weighted threshold secret sharing scheme based on the Chinese remainder theorem,we construct a weighted threshold access structure.Furthermore,we propose a weighted threshold authenticated encryption(CWAE) scheme.In the proposed scheme,each group member is assigned a positive weight according to its significance.A subset of the group can generate the signature-ciphertext if and only if the sum of weights assigned to its members exceeds a certain threshold.

Contract signature in e-commerce

In this paper, we propose a notion of contract signature used in e-commerce applications. We propose a contract signature scheme based on the discrete logarithm assumption. The contract signature scheme adopts a digital multi-signature scheme in public-key cryptography to facilitate fair signature exchange over network. This proposed solution allows multiple signers of a contract signature to exchange their partial signatures which are fully ambiguous for any third party (i.e., 1 out of ∞ ambiguity) to construct a valid contract signature. In case any signer releases the partial signature to others, the signer does not bind to the contract.

Efficient Blind Signature Scheme based on Modified Generalized Bilinear Inversion for Multiple Signers

As a special anonymous signature, the blindness of blind signatures makes it to play an important role in electronic commerce. Sometimes, we need a blind signature under the multiple signers. However, to the best of our knowledge, the research on the blind signer for multiple signers is much less. In this paper, we propose a novel blind signature scheme for multiple signers based on a new security assumption. Then, we give a formal proof of security for the proposed schemes in the random oracle model. And we show that the proposed scheme satisfies the two properties of blind signature: blindness and unforgeability. As for the size of blind signature in the scheme, the length of our blind signature is independent of the numbers of signers and is approximate 320 bits. In terms of computation, no pairings operators are required in the blind signing phase and one pairing operator is needed in the verification phase. Thus, our scheme is very efficient.

A novel multisignature scheme for a special verifier group against clerk and rogue-key attacks

The digital signature is a very important subject for network security. Considering multiple signers and multiple verifiers, Xie and Yu (2004) pointed out that the multisignature scheme of Laih and Yen (1996) is vulnerable to a harmful attack. An attack can occur when a specified group of verifiers cooperate to forge a multisignature by secret key substitution following the leak of a secret key or by group public key adjustment during the process of renewing membership. Xie and Yu proposed an improvement of Laih and Yen’s multisignature scheme. In this paper, we show that Xie and Yu’s scheme is vulnerable to clerk and rogue-key attacks. We propose an improved multisignature scheme to resist such attacks. In the proposed scheme, multiple signers can generate a multisignature for the message with the signers’ secret keys, and the specified group of verifiers can cooperate to verify the validity of the multisignature with the signers’ public keys and the verifiers’ secret key. The proposed scheme for a special verifier group not only has the advantages of Xie and Yu’s scheme, but also is secure against clerk and rogue-key attacks.