PHE: An Efficient Traitor Tracing and Revocation for Encrypted File Syncing-and-Sharing in C loud

Abstract— Recently, many more enterprises have moved their data into the cloud by using file syncing and sharing (F SS) 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 F SS service. This issue u sing a new system model with anomaly detection, tracing and revoking traitors. To implement this model, we p resent a new threshold cryptosystem, called Partially-ordered Hierarchical Encryption (PHE), which implements the par ti al-order key hierarchy, similar to role hierarchy in Hierarchical RBAC, in public-key infrastructure. 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: dynamic joining and revoking users, constant-size cipher texts and decryption keys, lower over loads for large-scale systems. < final year projects >