Biblio

Ciphertext-policy Attributes-based Encryption (CP-ABE) is an encouraging cryptographic mechanism. It behaves an access control mechanism for data security. A ciphertext and secret key of user are dependent upon attributes. As a nature of CP-ABE, the data owner defines access policy before encrypting plaintext by his right. Therefore, CP-ABE is suitable in a real environment. In CP-ABE, the revocation issue is demanding since each attribute is shared by many users. A policy-based revolutionary CP-ABE scheme is proposed in this paper. In the proposed scheme, revocation takes place in policy level because a policy consists of threshold attributes and each policy is identified as a unique identity number. Policy revocation means that the data owner updates his policy identity number for ciphertext whenever any attribute is changed in his policy. To be a flexible updating policy control, four types of updating policy levels are identified for the data owner. Authorized user gets a secret key from a trusted authority (TA). TA updates the secret key according to the policy updating level done by the data owner. This paper tests personal health records (PHRs) and analyzes execution times among conventional CP-ABE, other enhanced CP-ABE and the proposed scheme.

The key concerns in VANET communication are the security and privacy of the vehicles involved, but at the same time an efficient way to provide non-repudiation in the ad-hoc network is an important requirement. Most schemes proposed are using public key infrastructure (PKI) or symmetric key encryption to achieve security in VANET; both individually lack in serving the required purpose of providing privacy preservation of the involved On-Board Units (OBUs) (while still being able to offer non-repudiation) and amount to very sizeable overheads in computation. This paper proposes a privacy-preserving authentication protocol that employs hybrid cryptography, using the best features of PKI and symmetric cryptography to form a protocol that is scalable, efficient and offers services of integrity, non-repudiation, conditional privacy, and unlinkability; while still keeping the computational overhead at a reasonable level. The performance and security analysis of this scheme is provided to support the propositions.