Secure Key Storage and Access Delegation Through Cloud Storage

Abstract

Cloud storage is gaining popularity to store and share files. To secure the files, cloud storage providers supply client interfaces with the facility to encrypt the files and upload them into the cloud. When client-side encryption is done, the onus of key management lies with the cloud user. Public key proxy re-encryption mechanisms can be used to distribute the key among stakeholders of the file. However, clients use low powered devices like mobile phones to share their files. Lightweight cryptography operations are needed to carry out the encryption operations. Ring-LWE-based encryption scheme meets this criterion. In this work, a proxy re-encryption scheme is proposed to distribute the file key. The scheme is proved CCA secure under Ring-LWE assumption in the random oracle model. The performance of the scheme is compared with the existing proxy re-encryption schemes which are observed to show better performance for re-encryption and re-key generation.