Design System Of Electronic Seal Based On PKI And Digital Watermark

With the rapid development of OA(Office Automation),e-document transmits between different networks more and more frequently.E-document provides a shortcut of information transmition,but at the same time,it gives us some challenges:(1)How to make sure the real identity of the sender. (2)How to make sure the integrality of the document.(3)How to avoid the sender-refuses to admit that he is the sender of the document which is sent by himself.The purpose of the digital seal is to solve those problems,and it provides a safeguard for the transmission of the documents between different networks.This paper provides a scheme of digital seal system.the application of PKI architecture to provide for communications both public/private key that the encryption and decryption of data, and ensure the security of communications;through a summary of electronic signature documents to ensure that the amount of paperwork non-repudiation; stamping of electronic documents through the seal to ensure that the authority of the documents; the adoption of electronic seal embedded watermark, ensure security of electronic seals can not be copied and can not be deleted.A PKI is a pervasive security infrastructure whose services are implemented and delivered using public key concepts and techniques. The system provides the necessary services of confidentiality,integrity,authentication and non-repudiation for e-commerce by the standard API.As a identity authentication system,PKI provides the dependable security guarantee for network application.Digital watermark is a new and effective way to protect digital products and to maintain the data security.It is a very practical information hiding technique.Watermarking utilize a digital method to embed some markers which have special meanings into digital images,audio,documents,books and video. Watermarks can testify the ownership of the above.What is more,watermarks can also be the evidence in front of the court.In a word,digital watermarks can be an effective method to protect knowledge property and multimedia data.However,watermarks should not destroy the usefulness and the value of being viewed of the original data.The system used in watermarking algorithm is based on the discrete wavelet transform DWT Watermarking Algorithm.,Watermark embedding process is as follows:(1) Sampling the original image signal processing has been two-dimensional samplingⅠ;(2) Use N-level DWT transform of I to obtain the classification of subband coefficients of wavelet V_LL,V_LHⁱ,V_HLⁱ,V_HHⁱ,i=1,2,...,n,LL,LH,HL, HH,respectively, for the wavelet transform domain of the low-low-frequency sub-band, Low high-frequency sub-band, high-low-frequency sub-band, high-high-frequency sub-band,i is the wavelet decomposition level;(3) In accordance with the specified threshold in v_LHⁱ,v_HLⁱ,v_HHⁱ,i=1,2,...n Select the watermark to be adding the wavelet coefficients.Cycle by adding a watermark, Obtain sub-band coefficients of wavelet after adding a watermark v'_LHⁱ,v'_HLⁱ,v'_HHⁱ;(4) DWT domain of the images adjusted n-level inverse wavelet transform to be included in the watermark image.Watermark extraction process is as follows:(1) The original image I and the check images to be I ast, respectively, to handle two-dimensional sampling sampling signal I And I ast;(2) Respectively,I and I ast for n-level DWT Transform, has been the classification of sub-band coefficients of wavelet v_LHⁱ,v_HLⁱ,v_HHⁱ and v_LH^*i,v_HL^*i,v_HH^*i,i=1,2,...n,One of LL, LH, HL, HH, respectively, for the low-low-frequency wavelet sub-band, low-high-frequency sub-band, high-low-frequency sub-band, high-high-frequency sub-band, i Is the wavelet decomposition level;(3) In accordance with the specified threshold in v_LHⁱ,v_HLⁱ,v_HHⁱ,i= 1,2,...,n must select the wavelet coefficients,With v_LH^*i,v_HL^*i,v_HH^*i,i=1,2,...n the coefficient of the corresponding position in comparison,Extracted watermark information at all levels,among all sub-band of the watermark vector w_s^*=(w*_s1,w*_s2,...w*_sm)^T,s is each sub-band;(4) Calculation of the various sub-band to extract the watermark with the original watermark and all linear correlation Sub-band to extract the original watermark with the watermark of the total linear correlation. In the calculation of linear correlation, the sake of accuracy, we extract the watermark value filtering, a threshold greater than the correlation coefficient calculated not to participate in order to reduce the system found the probability of false.We adopt the threshold value is 2.5.