November 20, 2003Digital WatermarkingWatermarkingSlide 4Visible vs Invisible WatermarksRequirements of WatermarksWatermarking techniques For imageWatermarking for TextSteganographyExample of Steganography (Text – page 48)Slide 11What is Computer Forensics?Slide 13What is the Challenge?FBI List of Computer Forensic ServicesThe Coroner’s Toolkit (TCT) OverviewmactimeilsUnix fileIcat, fileunrmpcatgrave-robberLaw Enforcement ChallengesBroader Picture: What to DoSlide 26Risk ManagementRiskRisk Assessment/AnalysisBenefits of Risk AssessmentRisk Assessment stepsRisk Assessment steps (2)Example 1Example 2Example 2 (2)Some Arguments against Risk AnalysisRisk MitigationExamples of documented risk assessment systemsNSA ISSO Risk Assessment MethodologyThe NSA ISSO Risk Assessment ProcessThe Risk PlaneRisk IndexSlide 43Laws and SecurityCopyrightsCopyright infringementPatentSlide 48Trade SecretComparisonEmployee and Employer RightsSlide 52Slide 53Computer crimeComputer Crime related lawsEthicsLaw vs EthicsEthical reasoningEthics ExampleCodes of ethicsCourtesy of Professors Chris Clifton & Matt BishopINFSCI 2935: Introduction of Computer Security1November 20, 2003November 20, 2003WatermarkingWatermarkingComputer ForensicsComputer ForensicsRisk ManagementRisk ManagementLegal and Ethical IssuesLegal and Ethical IssuesLecture 12Lecture 12INFSCI 2935: Introduction to Computer Security 2Digital WatermarkingDigital WatermarkingA digital pattern or signal is inserted into A digital pattern or signal is inserted into an imagean imageCan serve as a digital signatureCan identify the intended recipient (unique to each copy)Can identify document source (common to multiple copies)INFSCI 2935: Introduction to Computer Security 3WatermarkingWatermarkingWatermarked image is transformed imageWatermarked image is transformed imageOriginal image remains intact, recognizablePersistent in viewing, printing and re-transmission and disseminationContrast to Contrast to fingerprintingfingerprinting and and encryptionencryptionIn digital fingerprinting, original file remains but a new file is created that describes the original file (e.g., checksum in Tripwire)Encryption transforms an image to an unrecognizable imageINFSCI 2935: Introduction to Computer Security 4WatermarkingWatermarkingVisible watermarksVisible watermarksSimilar to physical counterpart (digitally stamped!)Invisible watermarksInvisible watermarksUseful as for identifying the source, author, owner, distributor or authorized consumerPermanently, unalterably mark the imageAlso used for tracing images in the Also used for tracing images in the event of their illicit distributionevent of their illicit distributionUnique watermark for each buyerINFSCI 2935: Introduction to Computer Security 5Visible vs Invisible WatermarksVisible vs Invisible WatermarksPurpose visible invisiblevalidation of intended recipient - Primarynon-repudiable transmission - Primarydeterrence against theft PrimarySecondarydiminish commercial value without utilityPrimary Primarydiscourage unauthorized duplication Primary Secondarydigital notarization and authentication Secondary Primaryidentify source Primary SecondaryINFSCI 2935: Introduction to Computer Security 6Requirements of WatermarksRequirements of WatermarksTo protect intellectual propertyTo protect intellectual propertyWatermark must be difficult or impossible to remove, at least without visibly degrading the original imageWatermark must survive image modificationsAn invisible watermark should be imperceptible so as not to affect the experience of viewing Watermarks should be easily detectable by the proper authorityINFSCI 2935: Introduction to Computer Security 7Watermarking techniques For imageWatermarking techniques For imageSpatial domain watermarkingSpatial domain watermarkingSimplest: flip the lowest order bit of chosen pixelsSuperimpose a watermarkColor separation – watermark in only one color band-Picture cropping can be used to eliminate some spatial watermarkFrequency domain watermarkingFrequency domain watermarkingUse Fast Fourier Transform – alter the values of chose frequenciesWatermarks will be dispersed spatially (cropping or spatial technique will not defeat it)INFSCI 2935: Introduction to Computer Security 8Watermarking for TextWatermarking for TextText-line codingText-line codingText lines of a document page are shifted imperceptibly up or downWord-shift codingWord-shift codingSpacing between words in a line text is alteredCharacter codingCharacter codingE.g., endline at the top of a letter, say “t” is extendedINFSCI 2935: Introduction to Computer Security 9SteganographySteganographyArt of hiding information in the midst of Art of hiding information in the midst of irrelevant datairrelevant dataThis is NOT cryptographyThis is NOT cryptographyUseful to hide the existence of secret Useful to hide the existence of secret communicationcommunicationINFSCI 2935: Introduction to Computer Security 10Example of Steganography (Text – page Example of Steganography (Text – page 48)48)Dear George,Dear George,Greetings to all at Oxford. Many thanks for yourGreetings to all at Oxford. Many thanks for yourletter and for the summer examination package.letter and for the summer examination package.All entry forms and fees forms should be readyAll entry forms and fees forms should be readyfor final dispatch to the syndicate by Fridayfor final dispatch to the syndicate by Friday2020thth or at the latest I am told by the 21 or at the latest I am told by the 21stst..Admin has improved here though there is roomAdmin has improved here though there is roomfor improvement still; just give us all two or threefor improvement still; just give us all two or threemore years and we will really show you! Pleasemore years and we will really show you! Pleasedon’t let these wretched 16+ proposals destroydon’t let these wretched 16+ proposals destroyyour basic O and A pattern. Certainly thisyour basic O and A pattern. Certainly thissort of change, if implemented immediately, sort of change, if implemented immediately, would bring chaos.would bring chaos.Sincerely yours,Sincerely yours, yoyourur packagepackage readyready FridayFriday 2121stst.. roomroom threethree PleasePlease destroydestroy thisthisimmediatelyimmediatelyCourtesy of Professors Chris Clifton & Matt BishopINFSCI 2935: