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,*,按一下以編輯母片,第二層,第三層,第四層,第五層,按一下以編輯母片標題樣式,Applications of Data Hiding in Digital Images,自動化資訊處理實驗室,報告人,:,李惠龍,2,Outline,Introduction,Difference between cryptography and steganography,Applications,Covert communication,Digital watermarking,Watermarking for tamper detection and authentication,Our application,3,Steganography,The art of concealed communication,Hiding of secret messages within another message(or carrier),Make info.imperceptible,Keep existence of info.secret,4,Difference between cryptography and steganography,Cryptography:Protect the content of messages,Scramble data such that it is unreadable,Ciphertext attracts attackers for decryption,Steganography:Conceal the existence of messages,Hide data in another data,Hide the existence of communication,Stegotext minimizes attackers interest,5,Difference between cryptography and steganography,A secure crypto-system,One in which an adversary who understands the system,but does not know the key,can not recover the data,A secure stego-system,One where an adversary who understands the system,but does not know the key,can obtain no evidence that a communication has taken place,6,Robustness,The ability to extract hidden information after common image processing operations:,linear and nonlinear filters,lossy compression,contrast adjustment,recoloring,resampling,scaling,rotation,noise adding,cropping,printing/copying/scanning,D/A,and A/D conversion,pixel permutation in small neighborhood,color quantization(as in,palette images),skipping rows/columns,adding rows/columns,frame swapping,frame averaging(temporal averaging),etc.,Undetectability,Impossibility to prove the presence of a hidden message.This concept is inherently,tied to the statistical model of the carrier image.The ability to detect the presence does,not automatically imply the ability to read the hidden message.Undetectability should,not be mistaken for invisibility,a concept related to human perception.,Invisibility,Perceptual transparency.This concept is based on the properties of the human visual,system or the human audio system.,Security,The embedded information cannot be removed beyond reliable detection by targeted,attacks based on a full knowledge of the embedding algorithm and the detector,(except a secret key),and the knowledge of at least one carrier with hidden message.,Properties of hiding schemes,7,Applications,Covert communication(steganography),Digital watermarking(robust message embedding),Copyright protection of digital images(authentication),Fingerprinting(traitor-tracing),Adding captions to images,additional information to videos,Watermarking for tamper detection and authentication,8,Covert Communication,Purpose:,To conceal the very presence of communication,to make the communication invisible.,Encryption:,To make the message unintelligible,Secret communication?!,I just posted a picture of my,cat on my web page!,Warden,Willie,Andy,Bob,9,Covert,Communication,Secret,message,Encryption,Unit,Carrier,Image,Embedding,Algorithm,Modified,Carrier,-,Encryption,and steganography,provide double protection,-Randomized message is easier,to hide,10,Copyright protection of digital images(authentication),Original,+,=,Watermark,Watermarked,image,Robustness,against all kinds of,image distortion,Robustness to,intentional removal,even when all details,about the watermarking scheme are known(Kerckhoffs,principle),Watermark pattern must be,perceptually transparent,Watermark depends on a,secret key,Robustness to,over-watermarking,collusion,and other,attacks,11,Robust,secure,invisible watermark,resistant with respect,to the collusion attack(averaging copies of documents with,different marks).,Fingerprinting or traitor tracing,Marking copies of one document with a customer signature.,W,1,W,2,W,N,N,customers,+,original,12,Typical application:,Adding subtitles in multiple languages,Additional audio tracks to video,Tracking the use of the data(history file),Adding comments,captions to images,Watermark requirements:,Moderately robust scheme,Robustness with respect to lossy compression,noise adding,and A/D D/A conversion,Original images(frames)not available for message extraction,Security requirement not so strong,Fast detection,watermark embedding can be more time,consuming,Adding captions to images,additional information to videos,13,Watermarking for tamper detection and authentication,Watermarked image,altered image,Verification result,14,Our application,Sensitive information that is not encrypted(or that is encrypted with poor cryptographic techniques)and that is transmitted between two wireless devices may be intercepted and disclosed.,Provide a secret communication channel,Under application layer,Provide double protection(encryption and steganography),15,Our application,Wireless network,16,References,www.lib.nctu.edu.tw/new/data/,數位典藏版權,保護技術,.pdf,www.ws.binghamton.edu/fridrich/Research/tutor1.ppt,
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