summary [sss transcoding w/o decryption]

Secure Scalable Streaming (SSS)

Keywords

- secure scalable packets using jointly designed scalable coding and progressive encryption techniques

- has unencrypted headers that can provide hints

- has low complexity and can support many simultaneous transcoding sessions

- Motion JPEG-200, 3D subband coding, MPEG-4 FGS

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(1) scalability - to enable streaming to a multitude of clients with different device capabilities

(2) efficiency - to maximize the utility of available network and device resources

(3) security - to protect content from eavesdroppers

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scalable coding

- encodes a video sequence into a scalable bitstream
- first segment of the scalable bitstream can be used to decode baseline-quality video
- progressively longer segments can be used to decode progressively improved video
- video quality ---> spatial resolution, bit plane resolution, frame rate

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progressive encryption (encrypt and decrypt sequentially)

- bitstream could be divided into small blocks which are encrypted independently
- large degree of security ---> encrypting small blocks sequentially and feeding the encrypted data of earlier blocks into the encryption of later blocks
- first small block of ciphertext is decrypted into plaintext, second block of ciphertext is decrypted and the result is XORed ---> until the entire message is encrypted
- stream ciphers encrypte plaintext into ciphertext one bit a time

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sss coding and transcoding

- scalable coding, packetization, progressive encryption combined into code video into secure scalable packets
- characteristics : (1) scalable - enable downstream transcoding with packet truncation (2) encrypted - end-to-end security (3) independently decodable - resilient to errors such as packet loss

coding ------
- if the coded data will not fit into a single facket, modifications will have to be made
- input video ---> regions ---> scalable video data + header data ---> encrypted with progressive encryption ---> scalable packets (unencrypted header data + progressive scalable video data)

transcoding ------
- read header data ---> discard/truncate packets ---> decrypt and decode received packets
- resolution and quality of the reconstructed video will depend on the transcoding operation