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To address the limitations of the Raft consensus algorithm, such as the lack of support for Byzantine fault tolerance, performance bottleneck of the leader single node, and high leader election delay, an improved Byzantine fault tolerance consensus algorithm called RaBFT based on Raft is proposed. The distribution process of log messages is optimized by utilizing the secret sharing technique to make it Byzantine fault tolerance, and the role of the committee is introduced to share the communication pressure of the leader, thereby resolving the performance bottleneck issue of the leader single node. The leader election algorithm based on a dynamic committee improves the speed of leader election and reduces the time required for leader election. The experimental results show that RaBFT algorithm has a significant improvement in throughput and consensus delay in the log replication phase, and has a lower leader election delay, RaBFT algorithm can improve the efficiency and performance of the system, it is a safe and efficient consensus algorithm. [ABSTRACT FROM AUTHOR]

We propose a verifiable (t,n)-threshold secret sharing scheme using Lagrange interpolation and secure cryptographic hash functions. This scheme is an improvement of Shao’s scheme [Inform. Sci. 278 (2014) 104–109]. In our variant, verification of shares is achieved through computation of their multiplicative inverses in conjunction with a secure hash function such as SHA-3. This idea results in a significant size reduction, in comparison with Shao’s scheme, to the shares assigned to each participant. Applications of the proposed scheme include sharing of cryptographic keys, access codes, etc. Furthermore, we improve our construction to present a method for secret sharing with adjustable access structure. This can further be extended to a secret sharing scheme with essential participants, where any authorized set of participants must meet a threshold in the number of essential participants it contains. While our proposal has smaller share sizes compared to Shao’s scheme, it also adds the capabilities of changeable parameters and essential participants. [ABSTRACT FROM AUTHOR]

The interplanetary File system (IPFS) provides data communication using plaintext over distributed and decentralized systems. Up till now, the security of data has mostly been established using keys. To facilitate classified data communication within a Closed User Group (CUG), services of IPFS private swarm are required to render additional content encryption. Currently, there is no inherent security built into IPFS. This paper presents an application DMaya on IPFS to provide keyless encryption on IPFS based on the Quasigroup-based Secret Sharing Scheme (QSS). IPFS is used as a storage medium, irrespective of the nature of data. Data security in decentralized mode with IPFS is provided with DMaya. The classified data of all types (i.e. video data, audio data, text data, and image data) when subjected to DMaya application, are fragmented into smaller fragments then processed by the probabilistic Quasigroup-based Secret Sharing (QSS) Scheme. DMaya keyless encryption generates the metadata tag file at the source node. The recipient node within the same private IPFS swarm, on receipt of metadata tag file reconstructs the original data with DMaya application. [ABSTRACT FROM AUTHOR]

In a verifiable secret sharing (VSS) scheme, each participant can check cheating by the dealer or the other participants. In this work, we construct a VSS scheme with the strongest level of computational security and prove its security in the standard model. This scheme is secure against active attack and does not use bilinear pairing and hash function. [ABSTRACT FROM AUTHOR]

Vehicular ad hoc networks (VANET) is seen as an effective solution to ensure the driving safety and efficiency. As a key foundation, the road side unit (RSU) connect with each other to form a backbone network in VANET. The authentication of RSUs is the main tasks to prevent the secure communication in VANET suffering from various attacks caused by cunning adversaries. In this paper, we propose a new type of verifiable secret sharing (VSS) scheme based on bivariate polynomial to achieving the RSU authentication in a secret sharing way. Our proposed VSS based authentication includes two phases. In phase 1, the t RSUs that participate in secret reconstruction collaborate to detect whether there exist illegitimate ones; in phase 2, the t legitimate RSUs reveal their shares for secret reconstruction, and the fake shares can be identified. Our VSS facilitates the RSU authentication since (1) any RSUs participate in secret reconstruction can be confirmed legitimate, (2) any fake shares revealed in secret reconstruction can be identified, (3) a globalized group temporary session key will be established after the VSS process. In addition, our VSS scheme is unconditional secure since the security of our VSS is not based on any computational assumption. [ABSTRACT FROM AUTHOR]

Secret image sharing is a useful technique in various domains of image processing, like data hiding, image security, and visual authentication. It maintains the secrecy of an image by distributing it among many participants, known as shares. This article introduces a (n , n) singular value decomposition-based grayscale and color image-sharing techniques with verifiable and lossless reconstruction. A verifiable secret image sharing determines whether the reconstructed image is the original secret. The addition of all n shares is sufficient to reveal the secret image with no loss of information. Encryption before sharing and decryption after the addition of shares have been applied to resist information leakage of the reconstructed image by adding less than n shares. The verifiability, correctness, performance evaluation, and experimental security analysis of the proposed VSBSIS scheme have established its efficiency. Comparison with other contemporary polynomial-based secret image-sharing schemes demonstrates the efficient reconstruction of the proposed scheme. • Proposed VSBSIS has employed singular value decomposition (SVD) for making the shares. • Encryption and decryption have been applied to prevent information leakage. • A lossless reconstruction is achieved with the stacking of all shares. • Discrete logarithm has been utilised to verify the reconstructed image. • It overcomes the traditional drawbacks of a secret image sharing scheme. [ABSTRACT FROM AUTHOR]

Recently group-oriented applications over unsecure open networks such as Internet or wireless networks have become very popular. Thus, group communication security over unsecure open networks has become a vital concern. Group key establishment (GKE) protocols are used to satisfy the confidentiality requirement of a newly started communication session by the generation or sharing of an ephemeral common key between the group members. In this study, we analyze the computation and communication efficiency of GKE protocols. Besides confidentiality, the security characteristics of identification and integrity control are also required for all steps of the protocol implementations. Thus, the main contribution of this work is to provide the computation and communication efficiency analysis of the same GKE protocols along with the identification of the group entities and integrity control of messages during the protocol steps. The specific implementation and analysis of GKE protocols are performed by group key agreement (GKA) with pairing-based cryptography and group key distribution (GKD) with verifiable secret sharing, respectively. Finally, a comparison of GKA and GKD protocols on the basis of their strong points and cost characteristics are also provided to inform potential users. [ABSTRACT FROM AUTHOR]

Dynamic threshold public-key encryption, proposed by Delerablée and Pointcheval (CRYPTO 2008), is an extension of ordinary threshold encryption which enables decryption servers to join the system even after the setup phase, and to choose the authorized set and the threshold of decryption dynamically. Delerablée and Pointcheval proposed the first dynamic threshold public-key encryption scheme, which they proved secure under a non-standard q -type assumption. However, decryption consistency, which is an important security property that guarantees uniqueness of decryption, even when a sender and decryption servers behave maliciously, is only shown to hold in the random oracle model. In this paper, we propose three threshold public-key encryption schemes. The first and second schemes are both dynamic schemes. The former achieves a relatively weaker variant of decryption consistency, while the latter achieves a strong variant thereof. The former is a generic construction from public-key encryption with non-interactive opening (PKENO), while the latter is a specific construction from a standard number-theoretic assumption. These are the first constructions of dynamic public-key encryption, which achieve decryption consistency without relying on the random oracle model. Furthermore, both schemes can be realized based on standard assumptions. The third construction is a generic construction from PKENO achieving the strong variant of decryption consistency. This construction affirmatively answers the question indirectly posed by Galindo et al. (AFRICACRYPT 2010) of whether a generic construction achieving strong decryption consistency is possible. [ABSTRACT FROM AUTHOR]

A verifiable secret redistribution (VSR) scheme is a verifiable secret sharing scheme in which the shareholders can redistribute the secret from an old (t , n) -threshold access structure to a new (t ′ , n ′) -threshold access structure without reconstructing the secret and without interacting with the dealer. There exists an important flaw in the previous VSR schemes which has not been addressed by now: During redistributing the secret from an old (t , n) -threshold access structure to a new (t ′ , n ′) -threshold access structure, n t − n − t + 1 t restarts of the secret redistribution phase, in the worst case, are required to eliminate faulty shareholders and complete the secret redistribution phase. In this paper, we propose a new VSR scheme using Homogeneous linear recursions (HLR) and prove its security. Our scheme has the following interesting properties: First, it addresses the mentioned flaw of the previous VSR schemes without relaxing the security. Second, it does not have any restart and is more efficient than the previous VSR schemes. Finally, without observing the produced shares and sub-shares, the honesty of the dealer and shareholders can be verified publicly. [ABSTRACT FROM AUTHOR]

A distributed signature scheme allows participants in a qualified set to jointly generate a signature which cannot be forged even when any unqualified set of participants collude together. In this paper, we propose an efficient scheme that supports any monotone access structures and show its unforgeability and robustness under the computational Diffie–Hellman (CDH) assumption in the standard model. For 192-bit security, its secret key shares and signature fragments are as short as 511 bits and 1022 bits, which are shorter than existing schemes assuming random oracle. We then propose two extensions. The first one allows new participants to dynamically join the system without any help from the dealer. The second one supports a type of multipartite access structures, where the participant set is divided into multiple disjoint groups, and each group is bounded so that a distributed signature cannot be generated unless a pre-defined number of participants from multiple groups work together. Finally, we present a fully distributed signature scheme such that the centralized trusted dealer can be removed from the system, and the secret keys (shares) can be jointly computed by the involved participants. [ABSTRACT FROM AUTHOR]

We propose a novel verifiable (t,n)-threshold secret sharing construction using simple cryptographic building blocks. The proposed construction provides an extremely low computational cost with respect to most of existing schemes, since the sharing algorithm has a linear time complexity with respect to the number of participants and the size of the share, when the reconstruction algorithm complexity is constant with respect to the threshold t. Furthermore, the proposed construction is provably secure, and has been shown to be robust, confidential, ideal and traceable. An instance of the proposed construction is implemented using a combination of the CRT-based sharing scheme and the Salsa20 stream cipher. Experimental results and comparisons with existing approaches shows that the proposed approach provides very competitive performances, hence is very suitable to share large sized secrets such like digital images. [ABSTRACT FROM AUTHOR]

In a conventional quantum ( k, n) threshold scheme, a trusted party shares a quantum secret with n agents such that any k or more agents can cooperate to recover the original secret, while fewer than k agents obtain no information about the secret. Is the reconstructed quantum secret same with the original one? Or is the dishonest agent willing to provide a true share during the secret reconstruction? In this paper we reexamine the security of quantum ( k, n) threshold schemes and show how to construct a verifiable quantum ( k, n) threshold scheme by combining a qubit authentication process. The novelty of ours is that it can provide a mechanism for checking whether the reconstructed quantum secret is same with the original one. This mechanism can also attain the goal of checking whether the dishonest agent provides a false quantum share during the secret reconstruction such that the secret quantum state cannot be recovered correctly. [ABSTRACT FROM AUTHOR]

Based on Lagrange interpolation formula and the post-verification mechanism, we show how to construct a verifiable quantum ( k, n) threshold secret key sharing scheme. Compared with the previous secret sharing protocols, ours has the merits: (i) it can resist the fraud of the dealer who generates and distributes fake shares among the participants during the secret distribution phase; Most importantly, (ii) It can check the cheating of the dishonest participant who provides a false share during the secret reconstruction phase such that the authorized group cannot recover the correct secret. [ABSTRACT FROM AUTHOR]

Lin and Wu [IEE Proc. Comput. Digit. Tech. 146 (1999) 264] have proposed an efficient (t,n) threshold verifiable multi-secret sharing (VMSS) scheme based on the factorization problem and the discrete logarithm modulo a large composite problem. In their scheme, the dealer can arbitrarily give any set of multiple secrets to be shared, and only one reusable secret shadow is to be kept by every participant. On the other hand, they have claimed that their scheme can provide an efficient solution to the cheating problems between the dealer and any participant. However, He and Wu [IEE Proc. Comput. Digit. Tech. 148 (2001) 139] have shown that Lin and Wu''s scheme is in fact insecure against a cheating participant. In this paper, we shall try to improve the security of Lin and Wu''s scheme while providing more efficient performance than other VMSS schemes in terms of computational complexity. [Copyright &y& Elsevier]

A (t, n) threshold proxy signature scheme allows any t or more proxy signers to cooperatively sign messages on behalf of an original signer, but t-1 or fewer proxy signers cannot. Sun et al. proposed a new (t, n) threshold proxy signature scheme based on Zhang''s threshold proxy signature scheme. Recently, Hsu et al. pointed out that Sun''s scheme suffered from a drawback and proposed an improvement to counter it. However, the author of this paper shows that both Sun''s scheme and Hsu''s improvement are not secure against coalition attack. Some t or more malicious proxy signers can conspire together against the original signer. Finally, we propose a new improvement to counter this attack, the proxy generation and the signature computation of which is more efficient than those of Sun''s scheme and Hsu''s improvement. The main advantage of the new improvement is traceability, by which the original signer can identify the actual signers that are anonymous to outsiders. [Copyright &y& Elsevier]

An original approach to establish a computationally secure and robust conference key between multiple users is presented, which is built on known secret sharing schemes and requires the authenticated and encrypted point-to-point channels between servers and users. By running of the protocol, every honest user of a given conference can get a common key, even a minority of the servers malfunction or misbehave. This scheme does not rely on any unproven cryptographic assumptions or on the availability of any tamper-proof hardware. By using zero knowledge proof any corrupted information and incorrect results can be detected. And by distributing the sensitive security information across several servers and never reconstructing any key at a single location, the compromise of a few servers will not compromise the privacy of any key. Analysis shows that under the assumption of a Diffle-Hellman decisional problem, a passive adversary gets zero knowledge about the conference key) and in the random oracle model, an active adversary cannot impersonate successfully. We have implemented the scheme in a distributed environment By conducting a number of experiments in the fault-free case and various fault scenarios, we show that it has an acceptable performance of practicability. [ABSTRACT FROM AUTHOR]

Recently, Sun et al. pointed out some weaknesses of Zhang’s threshold proxy signature scheme and a disadvantage of Kim’s threshold proxy signature scheme. They further proposed a new (t,n) threshold proxy signature scheme based on Zhang’s scheme to eliminate these drawbacks. Unfortunately, their scheme suffered from a weakness which is shown in this paper. The authors also propose an improvement to counter it. [Copyright &y& Elsevier]

Secret sharing of (k , n) -threshold is naturally used to assist in security-assurance applications in smart systems. It can ensure a high level of data security and reliability. Most of existing secret sharing schemes are employing interpolating polynomial or Chinese remainder theorem, while the hyperplane geometry of Blakley' s scheme has not been widely used. One of the reasons is that the hyperplane geometry-based scheme leaks information about the secret even via less than the threshold number of shadows. In this paper, we propose a novel secret sharing scheme based on the high-dimensional rotation paraboloid instead of the hyperplanes to overcome this weakness. The secret is corresponding to the unique focal point, and the shadows are corresponding to points on it. We prove that linearly independent k points can determine a unique (k − 1) -dimensional rotation paraboloid, which is the theoretical support of secret distribution and reconstruction. Moreover, we realize verification via two well-known terms: cheater identification and cheating detection. We identify the validity of shadows submitted by participants for cheater identification and verify whether the reconstructed secret is the original one or not for cheating detection, so that dishonest behavior in the secret sharing scheme can be detected. Security analysis shows our scheme is secure against different types of attacks. [ABSTRACT FROM AUTHOR]

• Participant can identify whether the combiner from which shares submission requests are coming, is valid or not. • A combiner can also detect whether any cheating occur while receiving shares from the participants. • Participant do not get the exact share and ID. Thus it is impossible to retrieve the secret by k participants, accumulating their shares beyond the knowledge of the combiner. • The security analysis of the proposed method against different security threats proves its resistance against those threats. In threshold secret sharing (SS) scheme, widely known as (k, n) threshold secret sharing, a secret S is divided into n shares and distributed to participants by a dealer in such a way that S can successfully be retrieved by a combiner from k or more shares collected from participants, but fewer than k shares will get no information about the secret. Verifiable secret sharing (VSS) scheme adds verifiable feature to secret sharing mechanism to check whether the retrieved information is the original secret or not. It helps to avoid mishap before using the secret. VSS may also helps to identify the participant submitting wrong information. Cheating detection and cheater identification are two well known terms in verifiable secret sharing. The former finds whether the right secret is retrieved and the later detects the participant(s), who has/have submitted wrong share. In the current work we have proposed a verifiable secret sharing scheme with cheater identification facility. The scheme also facilitates combiner verification by the participants to check whether share submission request is coming from a valid combiner or not. Security analysis of the proposed scheme have proved its immunity against different types of attacks. [ABSTRACT FROM AUTHOR]

A (k , n) threshold secret image sharing (SIS) method is proposed to divide a secret image into n shadows. The beauty of this scheme is that one can only reconstruct a secret image with k or more than k shadows, but one cannot obtain any information about the secret from fewer than k shadows. In the (k , n) threshold SIS, shadow authentication means the detection and location of manipulated shadows. Traditional shadow authentication schemes require additional bits for authentication; need much information to be public; or need to put each shadow into a host image, utilizing the information hiding technique, which makes the generation, recovery and authentication complexity higher. Besides, most existing schemes work when a dealer participates in recovery. Our contribution is that we propose a SIS method for a (k , n) threshold with dealer-participatory and non-dealer-participatory mutual shadow authentication capabilities which integrates polynomial-based SIS and visual secret sharing (VSS) through using the result of VSS to "guide" the polynomial-based SIS by a screening operation. In our scheme, when an authentication image is public, all involved actors (participants and dealer) can mutually authenticate each other by exchange the lowest level plane instead of the whole shadow. Our scheme is suitable for the case with and without a dealer participate recovery. In addition, the proposed scheme has characteristics of low generation and authentication complexity, no pixel expansion, 100% detection rate and lossless recovery. [ABSTRACT FROM AUTHOR]

E-lottery schemes have attracted much interest from both industry and academia recently, because they are not only useful to raise funds for charity institutions, but also can be used as the major building blocks to design micro-payment systems. In the literature, a number of e-lottery schemes have been introduced over the last two decades. However, most of these schemes rely on some computational assumptions. In this paper, we introduce a novel e-lottery scheme that achieves information theoretical security. Our proposed scheme is designed using symmetric bivariate polynomials, and it satisfies the required security properties, such as correctness, unpredictability, verifiability, and robustness. Moreover, the winning number is generated in a distributed fashion, so that no trusted third party needs to be involved and the danger of a single point of failure is minimized. [ABSTRACT FROM AUTHOR]