MPEG-4 has recently adopted the Fine Granularity Scalability (FGS) video coding technology which enables easy and flexible adaptation to bandwidth fluctuations and device capabilities. Encryption for FGS should preserve such adaptation capabilities and allow intermediate stages in the delivery to process the media on the ciphertext directly. In this paper, we propose a novel scalable access control scheme with this property for the MPEG-4 FGS format. It offers free browsing of the lowquality base layer video but controls the access to the enhancement layer at different service levels based on either PSNR or bitrates. Both types of service levels are supported simultaneously without jeopardizing each other’s security. The scheme is fast and degrades neither compression efficiency nor error resilience of the MPEG-4 FGS. The approach is also applicable to other scalable multimedia. 1.

The recently proposed Scalable Multi-Layer FGS Encryption (SMLFE) [4][5] encrypts an MPEG-4 FGS stream into multiply PSNR and bitrate quality layers for layered access control. Both layer types are supported simultaneously. A simple key scheme was used in SMLFE. In this paper, we propose a novel key scheme for SMLFE that reduces the number of keys maintained and managed by a license server for each protected MPEG-4 FGS stream to two. The new key scheme needs only one key contained in a license to be sent to a consumer. This scheme is based on a cryptographic secure hash function and the Diffie-Hellman key agreement. It satisfies all the requirements of SMLFE and can be used to replace the original simple key scheme for SMLFE. The secure one-way hash and intractability of the Diffie-Hellman and the related problems of computing discrete logarithm ensure the security of the new key scheme. 1.