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This paper proposes a stack of three Byzantine-resistant protocols aimed to be used in practical distributed systems: multi-valued consensus, vector consensus and atomic broadcast. These protocols are designed as successive transformations from one to another. The first protocol, multi-valued consensus, is implemented on top of a randomized binary consensus and a reliable broadcast protocol. The protocols share a set of important structural properties. First, they do not use digital signatures constructed with public-key cryptography, a well-known performance bottleneck in this kind of protocols. Second, they are time-free, i.e. they make no synchrony assumptions, since these assumptions are often vulnerable to subtle but effective attacks. Third, they are completely decentralized, thus avoiding the cost of detecting corrupt leaders. Fourth, they have optimal resilience, i.e. they tolerate the failure of f = ?(n-1)/3? out of a total of n processes. In terms of time complexity, the multi-valued consensus protocol terminates in a constant expected number of rounds, while the vector consensus and atomic broadcast protocols have O(f) complexity. The paper also proves the equivalence between multi-valued consensus and atomic broadcast in the Byzantine failure model without signatures. A similar proof is given for the equivalence between multi-valued consensus and vector consensus. These two results have theoretical relevance since they show once more that consensus is a fundamental problem in distributed systems. [ABSTRACT FROM AUTHOR]

Due to its great efficiency and quantum resistance, public key cryptography based on Ring-LWE problem has drawn much attention in recent years. A batch of cryptanalysis works provided ever-improved security estimations for various Ring-LWE schemes, but few works discussed the security of Ring-LWE cryptography from kleptographic aspect. In this paper, we show how to embed a backdoor into a classic Ring-LWE encryption scheme so that partial bits of the plaintext are leaked to the owner of the backdoor. By theoretical analysis and experimental observations, we argue that the klepto Ring-LWE encryption scheme with such backdoor is feasible and practical. [ABSTRACT FROM AUTHOR]

In the identity-based broadcast encryption (IBBE), only these users whose identities are chosen in the ciphertext computing can decrypt the encrypted message. In this paper, we introduce an extension of IBBE, namely Identity-Based Broadcast Encryption for Inner Product (IBBE-IP), where message encryption is replaced by inner product encryption (IPE) introduced by Abdalla et al. (PKC 2015). Precisely, in the IBBE-IP, the private key is associated with a pair of an identity and a vector (I D , y →). The user with private key of (I D , y →) can decrypt the encrypted vector x → for an identity set S selected by the encryptor and learn the inner product 〈 x → , y → 〉 if and only if I D ∈ S. Differing from the IBBE, the decryption in the IBBE-IP yields the inner product associated with the encrypted vector without leaking any information of the vector. The encrypted vector is protected as long as the number of selected identities is less than their length. We present a construction of IBBE-IP with constant-size private keys and it supports unbounded private key queries, which was unachieved in the previous works of IPE in the public-key setting. The security of our proposed scheme is proved in the random oracle model. [ABSTRACT FROM AUTHOR]

In recent times, there has been increasing interest in storing data securely in the cloud environment. To provide owners of data stored in the cloud with flexible control over access to their data by other users, we propose a role-based encryption (RBE) scheme for secure cloud storage. Our scheme allows the owner of data to store it in an encrypted form in the cloud and to grant access to that data for users with specific roles. The scheme specifies a set of roles to which the users are assigned, with each role having a set of permissions. The data owner can encrypt the data and store it in the cloud in such a way that only users with specific roles can decrypt the data. Anyone else, including the cloud providers themselves, will not be able to decrypt the data. We describe such an RBE scheme using a broadcast encryption algorithm. The paper describes the security analysis of the proposed scheme and gives proofs showing that the proposed scheme is secure against attacks. We also analyse the efficiency and performance of our scheme and show that it has superior characteristics compared with other previously published schemes. [ABSTRACT FROM AUTHOR]

Attribute-based encryption with keyword search (ABKS) is a system that supports keyword search and access control. By inheriting from attribute-based encryption technology, most current ABKS schemes incur large computation costs in encryption phase and keyword search phase. In a typical implementation, the size of ciphertext is proportional to the number of attributes associated with the access policy, so that the keyword search time and the decryption time are proportional to the number of attributes used in the access policy. To deal with the above problem, we present a new ciphertext-policy attribute-based encryption with fast keyword search scheme. Our scheme preserves the fine-grained access control inherited from the ABE system while supporting hidden policy and fast keyword search. In particular, the proposed scheme can efficiently support AND-gate access policy with multiple attribute values. Moreover, our scheme features multi-value-independent which have constant computation costs compared with the existing ABKS schemes. With the “aggregation” technique, the keyword search phase only needs three pairings, which is a great advantage over previous ABKS schemes. We offer rigorous security proof of our scheme, and the performance analysis demonstrates the efficiency of our scheme. [ABSTRACT FROM AUTHOR]