Certificateless Encryption Schemes Strongly Secure in the Standard Model

This paper presents the first constructions for certificateless encryption (CLE) schemes that are provably secure against strong adversaries in the standard model. It includes both a generic construction for a strongly secure CLE scheme from any passively secure scheme as well as a concrete construction based on the Waters identity-based encryption scheme

Toward an RSU-unavailable lightweight certificateless key agreement scheme for VANETs

Vehicle ad-hoc networks have developed rapidly these years, whose security and privacy issues are always concerned widely. In spite of a remarkable research on their security solutions, but in which there still lacks considerations on how to secure vehicle-to-vehicle communications, particularly when infrastructure is unavailable. In this paper, we propose a lightweight certificateless and one-round key agreement scheme without pairing, and further prove the security of the proposed scheme in the random oracle model. The proposed scheme is expected to not only resist known attacks with less computation cost, but also as an efficient way to relieve the workload of vehicle-to-vehicle authentication, especially in no available infrastructure circumstance. A comprehensive evaluation, including security analysis, efficiency analysis and simulation evaluation, is presented to confirm the security and feasibility of the proposed scheme

Relations among notions of complete non-malleability: indistinguishability characterisation and efficient construction without random oracles

We study relations among various notions of complete non-malleability, where an adversary can tamper with both ciphertexts and public-keys, and ciphertext indistinguishability. We follow the pattern of relations previously established for standard non-malleability. To this end, we propose a more convenient and conceptually simpler indistinguishability-based security model to analyse completely non-malleable schemes. Our model is based on strong decryption oracles, which provide decryptions under arbitrarily chosen public keys. We give the first precise definition of a strong decryption oracle, pointing out the subtleties in different approaches that can be taken. We construct the first efficient scheme, which is fully secure against strong chosen-ciphertext attacks, and therefore completely non-malleable, without random oracles.The authors were funded in part by eCrypt II (EU FP7 - ICT-2007-216646) and FCT project PTDC/EIA/71362/2006. The second author was also funded by FCT grant BPD-47924-2008

Practical Certificateless Aggregate Signatures From Bilinear Maps

Aggregate signature is a digital signature with a striking property that anyone can aggregate n individual signatures on n different messages which are signed by n distinct signers, into a single compact signature to reduce computational and storage costs. In this work, two practical certificateless aggregate signature schemes are proposed from bilinear maps. The first scheme CAS-1 reduces the costs of communication and signer-side computation but trades off the storage, while CAS-2 minimizes the storage but sacrifices the communication costs. One can choose either of the schemes by consideration of the application requirement. Compare with ID-based schemes, our schemes do not entail public key certificates as well and achieve the trust level 3, which imply the frauds of the authority are detectable. Both of the schemes are proven secure in the random oracle model by assuming the intractability of the computational Diffie-Hellman problem over the groups with bilinear maps, where the forking lemma technique is avoided

A Heterogeneous Systems Public Key Encryption with Equality Test in Smart City

Smart cities have been identified as areas which are urbanized and utilize diverse types of electronic data collection sensors that are used to oversee resources and assets efficiently. Smart meters are a unit of smart cities and they collect information about users and their consumption patterns. Consequently, the Internet of Things (IoT) being at a steady evolution has prompted multiple users into having their data collected from smart meters, stored on cloud servers. This is a way of saving costs and time involved in accessing the data. In spite of that, the cloud-assisted IoT faces privacy and security issues. This is as a result of the cloud servers possessing an untrusted nature. Due to this, it is essential for the data accumulated from the smart meters be encrypted hitherto outsourcing it to the cloud server. However, having encrypted data in the cloud server leads to a complication when it comes to accessing the data. For users who are on a different public key system, it becomes illogical for the users to first download the entire data on the cloud in order to access the required data. Therefore to resolve this issue, a heterogeneous systems public key encryption with equality test (HS-PKE-ET) scheme was proposed. The HS-PKE-ET scheme integrates certificateless public cryptography with equality test (CLC-ET) with the public key encryption with equality test (PKI-ET). This scheme allows an authorized cloud server to determine if two encryptions encrypted within heterogeneous systems possess equivalent messages. Basing on the random oracle model, the proposed scheme’s security is stated under the bilinear Diffie-Hellman assumption together with the computational Diffie-Hellman assumption. Ultimately the size of storage, computation complexities and properties with other related works are focused on and illustrations indicate our proposed scheme reflects a good performance

General Certificateless Encryption and Timed-Release Encryption

While recent timed-release encryption (TRE) schemes are implicitly supported by a certificateless encryption (CLE) mechanism, the security models of CLE and TRE differ and there is no generic transformation from a CLE to a TRE. This paper gives a generalized model for CLE that fulfills the requirements of TRE. This model is secure against adversaries with adaptive trapdoor extraction capabilities, decryption capabilities for arbitrary public keys, and partial decryption capabilities. It also supports hierarchical identifiers. We propose a concrete scheme under our generalized model and prove it secure without random oracles, yielding the first strongly-secure security-mediated CLE and the first TRE in the standard model. In addition, our technique of partial decryption is different from the previous approach