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Abstract Today, cloud storage services increased the popular for data storage in the cloud and retrieve from any location without any time limitations. One of the most important demands required in cloud is secured data transmission in un-trusted cloud applications. Particularly, secure and efficient multiparty communications in Untrusted Cloud Environments (UCE) attract widespread attentions. The equipment used in UCE have the particularity of being heterogeneous and UCE communication environment are asynchronous networks in which multiple users cannot transmit their messages simultaneously. How to ensure secure communication between these heterogeneous intelligent devices is a major challenge for multiparty communication applied in UCE. In such an asynchronous environment, the asynchronous transmission can cause security problems in cryptographic functions. Therefore, how to implement rational secret sharing (RSS) in an asynchronous model of the UCE networks has become a burning research topic. The RSS refers to finding a solution composed of strategies to encourage players in the secret reconstruction to act honestly even players are rational to act for their own interest. If each player plays the game for the best response to the best response of other players, the game is in Nash equilibrium. The objective of an RSS is to achieve the Nash equilibrium state corresponding to the global optima. In this paper, we propose an information-theoretic secure RSS in asynchronous model for UCE. Our design uses Petersen’s VSS to allow every player to divide his share into multiple pieces for other players. Then, shares can be revealed asynchronously. If any player acts maliciously, his share can be recovered by other players. This feature can encourage players to act honestly since any malicious action (i.e., either revealing a fake share or refusing to release one) is useless. Our scheme is practically valuable for secure group-oriented applications in UCE.

In $(k, n)$ threshold secret sharing, a secret is converted into $n$ shares such that any threshold $k$ or more shares allow for the reconstruction of this secret; however, the total storage cost increases. By contrast, asymmetric secret sharing reduces the total shares to be stored. When implementing secret sharing in the cloud, if malicious players submit forged shares during the reconstruction process, the reconstructed value will differ from the original secret. Therefore, a method that quickly verifies the integrity of the restored secret should be developed. Many research papers investigate cheater detection/identification for $(k, n)$ threshold secret sharing. However, most of them require additional information, such as an authenticator. Harn et al. proposed a method for cheat detection using only the shares for $(k, n)$ threshold secret sharing. In this study, we improved and extended the method proposed by Harn et al. to realize the detection and identification of shares forgery (cheating) in asymmetric secret sharing suitable for a cloud system. The proposed method uses the shares generated during asymmetric secret sharing to reconstruct and verify the secret. We also included an attack that assumes a cloud system and shows that most methods cannot work against it. Finally, we discussed the requirements for a secret sharing scheme suitable for the cloud and showed that the proposed method is ideal for use in a cloud environment.

A verifiable (t, n) threshold quantum secret sharing scheme with sequential communication was proposed recently. In this work, we analyze its security and then give two new participant attacks. Using the first participant attack, the first participant can obtain the dealer's secrets by himself with nonzero probability without being detected. Using the second participant attack, a dishonest participant can gain access to the dealer's secrets by himself in the secret reconstruction phase while he can make the other participants recover false secrets instead of the real ones without being detected. Furthermore, we present an effective way to prevent these attacks.

A publicly verifiable secret sharing (PVSS) scheme enjoys the public verification and the lower cost of communication than VSS scheme. However, the existing PVSS schemes cannot be applied in the scenarios of the devices with low computation ability and do not share the multiple secrets among all participants efficiently. In this paper, an efficient publicly verifiable multi-secret sharing scheme with outsourcing secret reconstruction is proposed. Each participant only spends a small amount of computational cost to recover multiple secrets because of the expensive burden of computation and verifiability is outsourced to the cloud service provider (CSP). Moreover, the CSP knows no information of the secrets, and the participants have the abilities to verify the returned result. We also prove that our scheme is secure under the hardness assumption of the discrete logarithm problem and the modified generalized bilinear inversion problem.

In this paper, we focus on the research of non-interactive secure multi-party computation. At first, we propose a fully homomorphic non-interactive verifiable secret sharing (FHNVSS) scheme. In this scheme, shareholders can generate shares of any-degree polynomials of shared numbers without interaction, and the dealer can verify the correctness of shares sent by shareholders without interaction. We implemented the FHNVSS scheme in Python with a detailed performance evaluation. According to our tests, the performance of FHNVSS is satisfactory. For instance, when the request is a 10-degree polynomial of secret value, generating a response takes about 0.0017263 s; verifying a response takes about 0.1221394 s; recovering a result takes about 0.0003862 s. Besides, we make an extension on the FHNVSS scheme to obtain a fully non-interactive secure multi-party computation, called AntNest. In the AntNest scheme, distrustful parties can jointly calculate a any-degree negotiated function, the inputs of which are inputs of all parties, without interaction, and each party can verify the correctness of responses sent by parties without interaction. To the best of our knowledge, it is the first work to realize that parties can jointly calculate any-degree function, the inputs of which are inputs of all parties, without interaction.

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.

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.