专题6：数字版权管理(英)

1、Topic-6:Digital Rights Management architecture of DRM system encryption technique digital signature digital watermarking technology the basic components of the DRM system Content Provider Content Operator Paycenter Content Consumer DRM system workflowSeveral ConceptsOriginal messageEncrypted message

2、encryption keydecryption keySymmetric Cryptography & Asymmetric Cryptographysymmetric cryptographyasymmetric cryptographymeaningsencryption key =decryption keyencryption key decryption keysecurityrely on cryptographic keyrely on computational complexityadvantagehigh speedhigh encryption intensit

3、ydisadvantagerely on communication securitylow speedarithmeticDES、IDEARSADES Arithmetic DES (Data Encryption Standard) Cryptographic key : 48 bits Plaintext : 64 bits Ciphertext : 64 bits Amount of cryptographic keys: 2567.21016IDEA Arithmetic IDEA (International Data Encryption Algorithm) Cryptogra

4、phic key : 128 bits Plaintext : 64 bits Ciphertext : 64 bits Amount of cryptographic keys: 21283.41038 AdvantagesRSA (Encryption & Decryption) RSA Three parameters: e, d, n Encryption ：y = xe (mod n) Decryption ：x = yd (mod n)RSA Arithmetic A pair of keys for each user：1） Public key: n = p q, p

5、and q are large primes;2） (n)=(p-1)(q-1)， e - 2, (n) 1 3） (ed)(mod (n)=1, compute d；4） (e,n) is public key，(d, n) is private key Ex. let p=3，q=17，choose e=5，compute (d, n), then encrypt x=2。 n = p q = 3 17 = 51 (n) = ( p-1 ) ( q-1 ) = 2 16 = 32 ( 5d) mod 32 = 1，so d = 13 y = xe ( mod n ) = 25 mod 51

6、 = 32 yd ( mod n )= 3213 ( mod 51 ) = 2 = xDigital Watermarking technology Features of Digital Watermarking Imperceptibility or Concealment Robustness Security Provability Features of Video Watermarking Real-time processing Immediately detectability Combines with video coding standard Contancy of vi

7、deo bit rate Busy detectability Fig.7.13 Universal Model of Digital WatermarkingDigital WatermarkingKeyWatermark Generation Algorithm Watermarking Embedding Subsystem Hidden CarrierWatermarking ExtractionSubsystemOriginal carrier objectPossible AttacksDigital WatermarkingKeyOriginal carrier objectOr

8、iginal Carrier Information (I)Sccret Key / Public Key (K)Watermark Embedding Algorithm (E)Watermark Generation Algorithm (G) Digital Watermarking (W)The Information Added Watermark ( )wIFig 7-14 The block diagram for embedding watermarkingEstimated Watermark ( ) /Similarity Detection (Sim)WDigital W

9、atermark (W) /Original Carrier Info (I)Sccret Key / Public Key (K)Infromation to be detected ( )Watermark Detection Algorithm (D) wIFig 7-15 The flow chart of detecting watermarkingEmbedding Algorithm of Image Digital Watermarking LSB( Least Significant Bits ) DCT(Discrete Cosine Transform )Embeddin

10、g and Extraction programs for Video Digital Watermarking Program one Program two Program threeReconstruction VideoEncoderOriginal VideoWatermark Embedding Scheme oneDecoderWatermark Embedding Scheme twoWatermark Embedding Scheme threeWatermark Extraction Scheme oneWatermark Extraction Scheme twoWatermark Extraction Scheme threeCompressed StreamFi