File Syncing-and-Sharing using Efficient Traitor Tracing and Revocation

Recently, many more enterprises have moved their data into the cloud by using file syncing and sharing (FSS) service, but bring-your-own-device (BYOD) policies and greatly increasing mobile devices have in fact raised a new challenge for preventing the player/decoder abuse in the FSS service. In this paper, we address this issue using a new system model with anomaly detection, tracing and revoking traitors. To implement this model, we present a new threshold cryptosystem, called Partially-ordered Hierarchical Encryption (PHE), which implements the partial-order key hierarchy, similar to role hierarchy in Hierarchical RBAC, in public-keyinfrastructure. This cryptosystem provides two security mechanisms, traitor tracing and revocation, to support efficient digital forensics.The security and performance analysis shows that our construction is threshold provably secure and has following features: dynamicjoining and revoking users, constant-size ciphertexts and decryption keys, lower overloads for large-scale systems.