Improvement on the Multihop Shareholder Discovery for Threshold Secret Sharing in MANETs

The collaboration of at least a threshold number of secret shareholders in a threshold secret sharing scheme is a strict requirement to ensure its intended functionality. Due to its promising characteristics, such a scheme has been proposed to solve a range of security problems in mobile ad hoc networks. However, discovering a sufficient number of secret shareholders in such dynamic and unpredictable networks is not easy. In this paper, we propose a more efficient shareholder discovery mechanism compared to our previous work. The discovery process is performed in a multihop fashion to adapt to the mobile ad hoc network environment. We introduce batch extension that gradually extends the shareholders＇ collaboration boundary by more than one hop at a time around the service requestor, to find at least the threshold number of the unknown shareholders. Through the batch extension, reply aggregation is applicable, hence reducing the redundancy use of reply routes, decreasing the required packet transmission, and lessening the service delay, compared to the previously proposed mechanism. Our simulation results show that, with the appropriate batch size, the latest mechanism is more efficient with an insignificant increase of control overhead.

Circular threshold quantum secret sharing

This paper proposes a circular threshold quantum secret sharing （TQSS） scheme with polarized single photons. A polarized single photon sequence runs circularly among any t or more of n parties and any t or more of n parties can reconstruct the secret key when they collaborate. It shows that entanglement is not necessary for quantum secret sharing. Moreover, the theoretic efficiency is improved to approach 100% as the single photons carrying the secret key are deterministically forwarded among any t or more of n parties, and each photon can carry one bit of information without quantum storage. This protocol is feasible with current technology.

Some Secret Sharing Schemes Based on the Finite Fields

A （t, n）--secret sharing scheme is a method of distribution of information among n participants such that t 〉 1 can reconstruct the secret but （t - 1） cannot. We explore some （k, n）--secret sharing schemes based on the finite fields.

Verifiable Secret Sharing Scheme Based on Certain Projective Transformation

The main purpose of verifiable secret sharing scheme is to solve the honesty problem of participants. In this paper, the concept of nonzero k-submatrix and theresidual vector of system of hyperplane intersecting line equations is proposed. Based on certain projective transformations in projective space, a verifiable (t, n)-threshold secret sharing scheme is designed by using the structure of solutions of linear equations and the difficulty of solving discrete logarithm problems. The results show that this scheme can verify the correctness of the subkey provided by each participant before the reconstruction of the master key, and can effectively identify the fraudster. The fraudster can only cheat by guessing and the probability of success is only 1/p. The design of the scheme is exquisite and the calculation complexity is small. Each participant only needs to hold a subkey, which is convenient for management and use. The analysis shows that the scheme in this paper meets the security requirements and rules of secret sharing, and it is a computationally secure and effective scheme with good practical value.

Improved quantum(t,n)threshold group signature

Threshold signature is an important branch of the digital signature scheme,which can distribute signature rights and avoid the abuse of signature rights.With the continuous development of quantum computation and quantum information,quantum threshold signatures are gradually becoming more popular.Recently,a quantum(t,n)threshold group signature scheme was analyzed that uses techniques such as quantum-controlled-not operation and quantum teleportation.However,this scheme cannot resist forgery attack and does not conform to the design of a threshold signature in the signing phase.Based on the original scheme,we propose an improved quantum(t,n)threshold signature scheme using quantum(t,n)threshold secret sharing technology.The analysis proves that the improved scheme can resist forgery attack and collusion attack,and it is undeniable.At the same time,this scheme reduces the level of trust in the arbitrator during the signature phase.

A distributed adaptive multi-hop certification authority schemefor mobile Ad Hoc networks

This paper theoretically analyzes a deficiency of the existing scheme, and proposes a distributed multi-hop certification authority scheme for mobile Ad Hoc networks. In our design, we distribute the certification authority functions through a threshold secret sharing mechanism, in which each node holds a secret share and multiple nodes jointly provide complete services. Certification authority is not limited in a local neighborhood but can be completed within multi-hop location. In addition, we replace broadcast by multicast to improve system performance and reduce communication overhead. This paper resolves some technical problems of ubiquitous certification authority services, and presents a wieldy multi-hop certification authority algorithm. Simulation results confirm the availability and effectiveness of our design.

A provable-secure and practical two-party distributed signing protocol for SM2 signature algorithm

Mobile devices are widely used for data access,communications and storage.However,storing a private key for signature and other cryptographic usage on a single mobile device can be challenging,due to its computational limitations.Thus,a number of(t,n)threshold secret sharing schemes designed to minimize private key from leakage have been proposed in the literature.However,existing schemes generally suffer from key reconstruction attack.In this paper,we propose an efficient and secure two-party distributed signing protocol for the SM2 signature algorithm.The latter has been mandated by the Chinese government for all electronic commerce applications.The proposed protocol separates the private key to storage on two devices and can generate a valid signature without the need to reconstruct the entire private key.We prove that our protocol is secure under nonstandard assumption.Then,we implement our protocol using MIRACL Cryptographic SDK to demonstrate that the protocol can be deployed in practice to prevent key disclosure.

Security of account and privacy of transaction for bitcoin

As a kind of cryptocurrency, bitcoin has attracted much attention with its decentralization. However, there is two problems in the bitcoin transactions ： the account security and transaction privacy. In view of the above problems, a new partially blind threshold signature scheme is proposed, which can both enhance the security of bitcoin account and preserve the privacy of transaction. Firstly, transaction amounts are encrypted by employing the homomorphic Paillier cryptosystem, and output address is disturbed by using one-time public key. Then the encrypted or disrupted transaction information is signed by multiple participants who are authorized by using threshold secret sharing. Compared with partially blind fuzzy signature scheme, the proposed scheme can fully preserve the transaction privacy. Furthermore, performance analysis shows that the proposed scheme is secure and effective in practical applications.

Ramp Scheme Based on CRT for Polynomial Ring over Finite Field

Chinese Reminder Theorem(CRT)for integers has been widely used to construct secret sharing schemes for different scenarios,but these schemes have lower information rates than that of Lagrange interpolation-based schemes.In ASIACRYPT 2018,Ning,et al.constructed a perfect(r,n)-threshold scheme based on CRT for polynomial ring over finite field,and the corresponding information rate is one which is the greatest case for a(r,n)-threshold scheme.However,for many practical purposes,the information rate of Ning,et al.scheme is low and perfect security is too much security.In this work,the authors generalize the Ning,et al.(r,n)-threshold scheme to a(t,r,n)-ramp scheme based on CRT for polynomial ring over finite field,which attains the greatest information rate(r−t)for a(t,r,n)-ramp scheme.Moreover,for any given 2≤r_(1)<r_(2)≤n,the ramp scheme can be used to construct a(r_(1),n)-threshold scheme that is threshold changeable to(r′,n)-threshold scheme for all r′∈{r_(1)+1,r_(1)+2,···,r_(2)}.The threshold changeable secret sharing(TCSS)scheme has a greater information rate than other existing TCSS schemes of this type.