40-bit encryption

About: 40-bit encryption is a research topic. Over the lifetime, 5434 publications have been published within this topic receiving 149016 citations.

Encryption schemes from bilinear maps

Abstract: Encryption schemes are designed to provide data confidentiality and are a fundamental cryptographic primitive with many applications in higher-level protocols. Groups with a bilinear map allow us to build public key encryption schemes with new properties that are otherwise difficult to obtain using groups without a bilinear map. We support our thesis by presenting two encryption schemes based on bilinear groups; the first is a partial solution to the open problem on doubly homomorphic encryption proposed by Rivest et al. in 1978, and the second is the most efficient hierarchical identity based encryption scheme to date. Our main result deals with homomorphic encryption. Using bilinear groups, we developed a homomorphic encryption scheme based on the subgroup decision complexity assumption; this encryption scheme is additively homomorphic and also possesses an additional limited (single) multiplicative homomorphism. Even with such limitations, our encryption scheme allows us to evaluate on encrypted inputs useful formulas such as polynomials of total degree at most two and dot products. Our encryption scheme also lends itself naturally to a secure function evaluation protocol for computing 2-DNFs, which can be used to improve private information retrieval protocols. Our second result deals with hierarchical identity based encryption (HIBE), a generalization of identity based encryption. In previous constructions for HIBE, the length of ciphertexts, as well as the time needed for decryption, grows linearly with the depth of the hierarchy. Our HIBE system has ciphertext size, as well as decryption cost, that is independent of the hierarchy depth. The principal applications for HIBE are forward secure encryption and public key broadcast encryption. Using our HIBE system instead of existing HIBE systems in these two applications results in substantial reductions in the ciphertext size of both these applications.

Benaloh's dense probabilistic encryption revisited

Abstract: In 1994, Josh Benaloh proposed a probabilistic homomorphic encryption scheme, enhancing the poor expansion factor provided by Goldwasser and Micali's scheme. Since then, numerous papers have taken advantage of Benaloh's homomorphic encryption function, including voting schemes, private multi-party trust computation, non-interactive verifiable secret sharing, online poker. In this paper we show that the original description of the scheme is incorrect, because it can result in ambiguous decryption of ciphertexts. Then we show on several applications that a bad choice in the key generation phase of Benaloh's scheme has a real impact on the behaviour of the application. For instance in an e-voting protocol, it can inverse the result of an election. Our main contribution is a corrected description of the scheme (we provide a complete proof of correctness). Moreover we also compute the probability of failure of the original scheme. Finally we show how to formulate the security of the corrected scheme in a generic setting suitable for several homomorphic encryptions.

Timed-release and key-insulated public key encryption

Abstract: In this paper we consider two security notions related to Identity Based Encryption: Key-insulated public key encryption, introduced by Dodis, Katz, Xu and Yung; and Timed-Release Public Key cryptography, introduced independently by May and Rivest, Shamir and Wagner. We first formalize the notion of secure timed-release public key encryption, and show that, despite several differences in its formulation, it is equivalent to strongly key-insulated public key encryption (with optimal threshold and random access key updates). Next, we introduce the concept of an authenticated timed-release cryptosystem, briefly consider generic constructions, and then give a construction based on a single primitive which is efficient and provably secure.

A Hybrid Scheme for Fine-Grained Search and Access Authorization in Fog Computing Environment.

Abstract: In the fog computing environment, the encrypted sensitive data may be transferred to multiple fog nodes on the edge of a network for low latency; thus, fog nodes need to implement a search over encrypted data as a cloud server. Since the fog nodes tend to provide service for IoT applications often running on resource-constrained end devices, it is necessary to design lightweight solutions. At present, there is little research on this issue. In this paper, we propose a fine-grained owner-forced data search and access authorization scheme spanning user-fog-cloud for resource constrained end users. Compared to existing schemes only supporting either index encryption with search ability or data encryption with fine-grained access control ability, the proposed hybrid scheme supports both abilities simultaneously, and index ciphertext and data ciphertext are constructed based on a single ciphertext-policy attribute based encryption (CP-ABE) primitive and share the same key pair, thus the data access efficiency is significantly improved and the cost of key management is greatly reduced. Moreover, in the proposed scheme, the resource constrained end devices are allowed to rapidly assemble ciphertexts online and securely outsource most of decryption task to fog nodes, and mediated encryption mechanism is also adopted to achieve instantaneous user revocation instead of re-encrypting ciphertexts with many copies in many fog nodes. The security and the performance analysis show that our scheme is suitable for a fog computing environment.