Study On Orthogonal Decomposition Based Commutative Encryption And Watermarking

The wide development of digital networking has brought great advantages for multimedia technology on the generation, storage and transmission as well as the great threat to the security:it’s easy to achieve the non-mark modification, complete copy and rapid spread of digital multimedia. Encryption and watermarking are the key technologies for the access security and the usage security of multimedia respectively. For the comprehensive security protection of multimedia, scholars suppose to integrate encryption and watermarking for the access security and the usage security in the same time.Commutative Encryption and Watermarking (CEW) is one of the effective way to integrate encryption and watermarking, which can achieve the commutation between encryption and watermarking:the generation of final encrypted-watermarked carrier wouldn’t be affected by the operation order of encrypting and watermark embedding, and the embedding information can be extraction from watermarked carrier no matter it is encrypted or not. Therefore, under the scheme of CEW, multimedia is protected by encryption for access security and watermarking for usage security. However, CEW is still in its infancy and there are many problems need to be studied.For the application requirements of CEW and the shortages of present algorithms, this paper proposes the technical model of applicable CEW, studies the implement of CEW based on orthogonal decomposition (CEWod), and designs the security services protocol based on CEWod. The main work in this paper includes:(1) Summarizing the requirements of applicable CEW according to the practical needs and then making up the applicable CEW model which can provide guidance for the following algorithm design. According to the proposed model, applicable CEW should achieve the operand mixture and the algorithm feasibility as well as the operation commutative of encryption and watermarking for the security and practicability.(2) Designing the applicable CEW based on the independence and integration of orthogonal decomposition and proposing the scheme of CEW based on orthogonal decomposition (CEWod). For the orthogonal decomposition coefficients being independent of each other and merging into composite vector, which is corresponding to the requirements of applicable CEW model, it’s absolutely possible to realize applicable CEW based on orthogonal decomposition to make up the shortage of current independent operands based CEW in security and the shortage of current independent mechanism based CEW in application.(3) Realizing the CEWod by normal encryption and watermarking algorithms for JPEG data stream and adjusting it as the requirements of remote sensing application to realize the remote sensing image commutative encryption and fingerprinting. In practical, multimedia almost needs data compression. And so this paper integrates AES encryption algorithm and DCT domain dither modulation to realize JPEG domain CEWod and discusses the problems in the realization such as the selection of ortho-base, the division of operand etc.(4) Designing the security service protocol based on CEWod. According to the requirements of current multimedia security service, this paper designs a new multimedia security service protocol based on CEWod:multimedia can be safely transferred by encryption, and in the same time, can be safely used by watermarking. What is more, the introduce of the third party can efficiently balance the two trading pertners’interest, however, the third party couldn’t gain any information about the multimedia.This paper summarizes the practical requirements of CEW and proposes the applicable CEW model which can provide reference for the design and realization of CEW algorithm. The practical CEW algorithm designed according to this model possesses the characteristics of commutativity, mixture and applicability. Furthermore, CEW is introduced into the multimedia security service for constructing a new third party protocol, which can provide comprehensive protection for multimedia transaction.