1 / 21

Transmisia datelor multimedia in retele de calculatoare Steganografia

UNIVERSITY POLITEHNICA of BUCHAREST DEPARTMENT OF COMPUTER SCIENCE. Transmisia datelor multimedia in retele de calculatoare Steganografia. Milas Iulian Constantin < iulian_milas@yahoo.com >. Introducere. Scopul steganorafiei ; Diferenta intre criptografie si steganografie ;

yanni
Download Presentation

Transmisia datelor multimedia in retele de calculatoare Steganografia

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. UNIVERSITY POLITEHNICA of BUCHAREST DEPARTMENT OF COMPUTER SCIENCE Transmisiadatelor multimedia in retele de calculatoareSteganografia MilasIulianConstantin <iulian_milas@yahoo.com>

  2. Introducere • Scopulsteganorafiei; • Diferentaintrecriptografiesisteganografie; • steganography_medium = hidden_message + carrier + steganography_key

  3. ClasificareaThenicilor de Steganografie

  4. Null Ciphers • Pe Internet spam-urilesuntpotentialepurtatoare de mesaje: Dear Friend , This letter was specially selected to be sent to you ! We will comply with all removal requests ! This mail is being sent in compliance with Senate bill 1621 ; Title 5 ; Section 303 ! Do NOT confuse us with Internet scam artists . Why work for somebody else when you can become rich within 38 days ! Have you ever noticed the baby boomers are more demanding than their parents & more people than ever are surfing the web ! etc. • Meet at Main and Willard at 8:30

  5. Metodefolosite in purtatoriidigitali:The Embedding Process

  6. Metodefolosite in purtatoriidigitali: Fingerprinting si Watermarking • Ceestefingerprinting? • CeesteWatermarking?

  7. Metodefolosite in purtatoriidigitali: Least Significant Bit Insertion #1

  8. Metodefolosite in purtatoriidigitali: Least Significant Bit Insertion #2 • Sa ascundemlitera “G” care are codul ASCII binar 01000111 • Fie secventa de octetidintr-o imagine : • Codarealui “G” peLSB:

  9. Metodefolosite in purtatoriidigitali: Public Key Steganography • Presupunem ca measajulestecodat cu o cheieprivata; • Dar unuldintreceidoi nu are decatcheiapublica; • Ce face primul? • Dar al doilea?

  10. Metodefolosite in purtatoriidigitali: Transform Domain Based Steganography • Algoritmii de extractie se impart in douagrupuri: - domeniuspatiu/timp; - domeniutransformare; • AlgoritmulPatchwork ;

  11. Metodefolosite in purtatoriidigitali:Diverse #1 • Spread-spectrum steganography – se bazeazapeportiunile de “energie” ridicata; • Ascundere a mesajelor in portiunileneutilizate ale headerelorfisierelor; • Folosireapartitiilor secrete de pe hard; • Micimodificari ale sunetului: siftarefaza, cadentavorbirii;

  12. Metodefolosite in purtatoriidigitali:Diverse #2 • Fisierele audio suntfoartebunepentruascunsmesajedeoarecesuntmari, iarinformatiaascunsa se vagasiigreu; • Steganografia nu estelimitatadoar la imaginisifisiere audio: - executabilele – Ex: redundantainstructiunilori386 ==> se pastreazasidimensiuneaoriginala a fisierului;

  13. DetectiaSteganografiei #1 • Steganaliza : - detecteazasauestimeazainformatiaascunsapebazaobservariiunortransferuri de date, farasafacavreopresupunereasupraalgoritmului de steganografie; • O prima metodaesteurmarirea “purtatorului”; • O altametodaesteurmarireamodificarilorstructurale ale “purtatorului”; • Tehnicilesteganograficealtereaza de obiceistatisticiledespre un “purtator”;

  14. DetectiaSteganografiei #2 • Steganalizaeste in general signature-based; • SteganalizaAnomaly-based – (blind steganalysis);

  15. Exemple de Steganografie • Vomascunde un GIF de 11,067 bytes intr-un GIF, JPEG si WAV; Fig 1:

  16. Imagine ascunsaintr-un GIF #1 • Fig urmeste o imagine a Washington DC ce confine Fig1. Imagineainitialaeste632,778 bytes sifoloseste 249 culoriunice; la final 677,733 bytes si 256 culoriunice; marimeaestemai mare din cauzafolosiriiextensiei de culori.

  17. Imagine ascunsaintr-un GIF #2 • Paleta de culori de la img Washington (purtatorul) inainte (stanga) sidupa (dreapta) ceFig1 a fostascunsa:

  18. Imagine ascunsaintr-un JPEG • Initial 207,244 bytes si 224,274 culoriunice; • Dupasteganografiere: 207,275 bytes si 227,870 culoriunice; • Nu putemvedeavreopaleta de culorideoarece JPEG folosestecodarea 24 bit-color siDCT;

  19. Imagine ascunsaintr-un WAV • Initial 178,544 bytes, iar WAV-ulsteganografiat 178,298 bytes :

  20. Concluzii • Teroristiisi eBay; • Dupa11 Septembrie 2001 s-au efectuatmultestudiipecontinutulInternetului: - s-au verificatmilioane de JPEG-uripe eBay ==> 1-2% din imaginieraususpecte – niciunmesajgasit; - alt studiu a examinatcatveasute de mii de imagini de pe diverse pagini Web alese random ==> rezultatesimilare; • Decinimicconcludent – doar JPEG-uri s-au verificat; numarscazut de site-uri; unelerapoarte pot fitinute secrete;

  21. Q&A

More Related