Scalable Contents Protection and Management
2005 . 07 ~ current
 
Scalable coding, Scalable coding is a technology that encodes a multimedia signal in a scalable manner where various representations can be extracted from a single codestream to fit a wide range of applications. current scalable codecs are JPEG2000(image), MPEG-4 FGS(Video), SVC(Scalable video coding). In this project, we research protection for scalable coding especially SVC
 
Fig. 1. SVC Adaptation
 
As Fig 1 showed, SVC encoded contents adapted by Extraction procedure. extraction conditions are various. e.g. terminal conditions, Network bandwidth, user preferences
 
Scalable Video Encryption, Multimedia Encryption different with Data encryption. because of large data size, multimedia contents encrypt selectively. encryption regions are multimedia dependent manner (e.g. video contents use I-frame, I-block or Motion Vector). moreover scalable contents provide scalability after encryption. In this project, We research SVC suitable encryption scheme
 
The goal of this project is the followings
 
1. Encryption for SVC bitstream
Encryption for SVC Extraction procedure
SVC format compliance encryption
 
2. Conditional access control
Access to certain spatial-temporal-quality layers
 
Fig. 2. SVC encryption and decyption
 
Fig 2  Shows flow of SVC bitstream. the bitstream flows Encoding, Encryption, Extraction, Decryption, Decoding. in this procedure encryption provide secure extraction. because extractions are possibly not trust, and encryption provide decoding without decryption. and
 
Requirement for SVC encryption
 
Consideration on encryption algorithm :
Encryption algorithm : symmetric key, Asymmetric Key
Encryption Region (Data encryption) : Naive algorithm, selective algorithm, scrambling
Encryption Region (Multimedia encryption) : I-Frame, I-block, Motion vector, Coefficient
 
 
Requirement for Selective Encryption
Visual leakage
Security
Encoder Complexity
Compression overhead
Format compliance
Scalability
 
 
NAL structure in the SVC bitstream
 
Fig. 3. SVC NAL structure and enhancement procedure
 
Fig. 3. shows NAL structure in the SVC Bitstream. SVC bitstream consist of Spatial-temporal-quality base layer and enhancing layer these layers decided encoding step. each NAL means each enhancing layer, and extraction performs NAL unit. therefore NAL units are fundamental encryption unit. moreover NAL unit encryptions are good for conditional access control
 
Conditional access control
 
Fig. 4. NAL unit encryption for conditional access control
 
Fig. 4. shows typical SVC bitstreams providing 2 spatial layer, 2 temporal layer, 2 quality layer. if these NAL encrypt different keys then contents provider can controls access certain spatial, temporal, quality layer using combination of keys
 
Spatial Quality 15 fps (0) 30 fps (1)
QCIF(0) Base(0) {k(0,0,0)} Not exist
FGS(1) {key(0,0,0),key(0,0,1)} Not exist
CIF(1) Base(0)
{key(0,0,0),key(0,0,1)
key (1,0,0) }
{key(0,0,0),key(0,0,1)
Key(1,0,0),key(1,1,0)}
FGS(1)
{key (0,0,0),k(0,0,1)
key (1,0,0),key(1,0,1)}
{key(0,0,0),key(0,0,1)
key(1,0,0),key(1,0,1)
key(1,1,1),key(1,1,0)}

 

 
Table. 1. Keys for access certain layer
 
Table 1. shows access key for certain layer in Fig 4 case. if client don't have enough keys then access denied
 
원용근, 배태면, 노용만, "암호화된 SVC 비트스트림에서 조건적 접근제어 방법에 관한 연구", 2005년도 정보처리학회 추계학술발표대회, V.12 No.2 p151-154, 2005.11
 

 

The adaptation process using SVC scheme &

conditional access control using a layered encryption for SVC contents