Multi-user file-sharing systems based on LWE

Multi-user file-sharing plays an important role in the cloud storage. It allows different users to share files via the cloud. However, it usually faces many security issues because the cloud is usually public and semi-trusted. To overcome these issues, we propose multi-user file-sharing systems (MFS) in this paper. According to the date sources, we propose two frameworks of MFS based on the framework of proxy re-encryption (PRE), unique source (uni-source) MFS and multi-source MFS. We formalize the security models, which contain ciphertext security, secret key security and master secret security. With the frameworks, we propose two secure and efficient MFS schemes based on LWE, the uni-source MFS UM and the multi-source MFS MM. We prove that UM is secret key and ciphertext security, and MM is secret key, master secret and ciphertext security with the hardness assumptions of LWE and SIS. Furtherly, we prove they have some useful properties, such as non-interactive and anonymous.