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Data Hiding,image hiding,watermarking

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  1. 1. Steganography By Harsh Madhani Computer Engineering Page 1
  2. 2. cryptography κρσπό ς γραυία hidden writingA secret manner of writing, … Generally, the art ofwriting or solving ciphers. — Oxford English Dictionary Page 2
  3. 3. cryptology κρσπός λογια hidden speaking1967 D. Kahn, Codebreakers p. xvi, Cryptology is thescience that embraces cryptography and cryptanalysis,but the term ‘cryptology’ sometimes loosely designatesthe entire dual field of both rendering signals secureand extracting information from them. — Oxford English Dictionary Page 3
  4. 4. Steganography στεγαμός γραυία covered writingThe art of secret (hidden) writing Page 4
  6. 6. Steganography Art and science of communicating in a way that hides the existence of a message signal or pattern imposed on content – persistent under transmission – not encryption • original image/file is intact – not fingerprinting • fingerprinting leaves separate file describing contents Page 6
  7. 7. • Steganography includes the concealment of information within computer files.• In digital Steganography, electronic communications may include steganographic coding inside of a transport layer, such as a document file, image file, program or protocol.• Media files are ideal for steganographic transmission because of their large size.• As a simple example, a sender might start with an innocuous image file and adjust the color of every 100th pixel to correspond to a letter in the alphabet, a change so subtle that someone not specifically looking for it is unlikely to notice it. Page 7
  8. 8. Classic techniques • Invisible ink (1st century AD - WW II) • Tatoo message on head • Overwrite select characters in printed type in pencil – look for the gloss • Pin punctures in type • Microdots (WW II) • Newspaper clippings, knitting instructions, XOXO signatures, report cards, … Page 8
  9. 9. Digital Steganography • Modern Steganography entered the world in 1985 with the advent of the personal computer being applied to classical Steganography problems. • Over 925 digital Steganography applications have been identified by the Steganography Analysis and Research Center.Digital Steganography techniques include: • Concealing messages within the lowest bits of noisy images or sound files. • Chaffing and winnowing. Page 9
  10. 10. • Concealed messages in tampered executable files, exploiting redundancy in the targeted instruction set.• Pictures embedded in video material (optionally played at slower or faster speed).• Injecting imperceptible delays to packets sent over the network from the keyboard.• Delays in keypresses in some applications (telnet or remote desktop software) can mean a delay in packets, and the delays in the packets can be used to encode data.• Image bit-plane complexity segmentation Steganography Page 10
  11. 11. Chaffing & Winnowing • Separate good messages from the bad ones • Stream of unencoded messages with signatures – Some signatures are bogus – Need key to test Alice Bob M3 M2 M1 M0 M3 M2 M1 M0 Irene × OK × × M3 M2 M1 M0 ? ? ? ? Page 11
  12. 12. Null Cipher • Hide message among irrelevant data • Confuse the cryptoanalyst Page 12
  13. 13. Null Cipher • Hide message among irrelevant data • Confuse the cryptoanalyst Big rumble in New Guinea. The war on celebrity acts should end soon. Over four big ecstatic elephants replicated. Page 13
  14. 14. Null Cipher • Hide message among irrelevant data • Confuse the cryptoanalyst Big rumble in New Guinea. The war on celebrity acts should end soon. Over four big ecstatic elephants replicated. Bring two cases of beer. Page 14
  15. 15. Network Steganography • Network Steganography utilizes communication protocols control elements and their basic intrinsic functionality. • Typical network Steganography methods involve modification of the properties of a single network protocol. • Moreover, it is feasible to utilize the relation between two or more different network protocols to enable secret communication. These applications fall under the term inter- protocol Steganography.[14] Page 15
  16. 16. • Steganophony - the concealment of messages in Voice-over-IP conversations, e.g. the employment of delayed or corrupted packets that would normally be ignored by the receiver (this method is called LACK - Lost Audio Packets Steganography), or, alternatively, hiding information in unused header fields. Page 16
  17. 17. Image watermarking • Spatial domain watermarking – bit flipping – color separation • Frequency domain watermarking – embed signal in select frequency bands (e.g. high frequency areas) – apply FFT/DCT transform first – e.g. Digimarc – watermark should alter the least perceptible bits • these are the same bits targeted by lossy image compression software Page 17
  18. 18. UV Watermarking Page 18
  19. 19. Machine ID codes in laser printers See Page 19
  20. 20. Machine ID codes in laser printers Page 20
  21. 21. Machine ID codes in laser printers Page 21
  22. 22. Machine ID codes in laser printers Page 22
  23. 23. Text • Text lines shifted up/down (40 lines text  240 codes) • word space coding • character encoding - minor changes to shapes of characters Page 23
  24. 24. Text • Text lines shifted up/down (40 lines text  240 codes) • word space coding • character encoding - minor changes to shapes of characters • works only on “images” of text e.g., PDF, postscript Page 24
  25. 25. Image SteganographyImage of a tree with asteganographically hidden Image of a cat extractedimage. The hidden image isrevealed by removing all but from the tree imagethe two least significant bits besides.of each color component and asubsequent normalization. Page 25
  26. 26. Audio Perceptual coding – inject signal into areas that will not be detected by humans – may be obliterated by compression Hardware with copy-protection – not true watermarking - metadata present on media – DAT – minidisc – presence of copy protection mechanisms often failed to give the media wide-spread acceptance Page 26
  27. 27. Video • Coding still frames - spatial or frequency • data encoded during refresh – closed captioning • visible watermarking – used by most networks (logo at bottom-right) Page 27
  28. 28. Data Embedding Security Schemes • One of the areas that improves steganographic robustness is usage of a key scheme for embedding messages.Key scheme term means a procedure of how to use key steganographic system based on the extent of its use. However, when the steganographic robustness is increased a bandwidth of the whole embedding system is decreased. Therefore the task of a scheme selection for achieving the optimal values of the steganographic system is not trivial. Page 28
  29. 29. The first level of protection is determined only by the choice ofembedding algorithm. This may be the least significant bitsmodification algorithm, or algorithms for modifying the frequency orspatial-temporal characteristics of the container. The first level ofprotection is presented in any steganographic channel.Steganographic system in this case can be represented as shown atThe First Protection Level Scheme figure. Page 29
  30. 30. The second protection level of the steganographic system, as well as all levels ofprotection of the higher orders, is characterized by the use of Key (password)via steganographic modification. An example of a simple key scheme, whichprovides a second level of protection, is to write the unmodified or modifiedpassword in the top or bottom of the message; or the distribution of thepassword sign on the entire length of the steganographic channel. Such keyschemes do not affect the distribution of messages through the container anddo not use a message preprocessing according to the defined key (see figure TheSecond Protection Level Scheme). This kind of steganographic systems are usedin such tasks as, for instance, adding a digital signature for proof of copyright.Data embedding performance is not changed in comparison with the fastestapproach of the first protection level usage. Page 30
  31. 31. Steganographic data channels that use key schemes based distribution of amessage through the container and or preprocessing of an embedded message fordata hiding are more secure. When the third protection level key scheme is usedit affects the distribution of a message through the container (see figure TheThird Protection Level Scheme, where F(P, L) – distribution function of a messagewithin a container; P – minimum number of container samples that are needed toembed one message sample; L – step of a message distribution within a container).Accordingly, the performance of container processing will be lower than in thecase of the first and the second key schemes. Taking into account that P≥L, thesimplest representation of the F(P, L) function could be as following:F(P, L) = cycle*L + step*P, Page 31
  32. 32. The difference between the fourth protection level scheme and thethird one is that in steganographic system there are twodistribution functions of a message within a container are used. Thefirst is responsible for a message samples selection according tosome function G(Q, N), and the second function F(P, L) is responsiblefor position selection in a container for message sample hiding. HereQ – the size of message block to be inserted; N – the size (in bits)of one sample of the message file (see figure The Fourth ProtectionLevel Scheme). Page 32
  33. 33. Countermeasures and detection • In computing, detection of steganographically encoded packages is called steganalysis. The simplest method to detect modified files, however, is to compare them to known originals. • For example, to detect information being moved through the graphics on a website, an analyst can maintain known-clean copies of these materials and compare them against the current contents of the site. The differences, assuming the carrier is the same, will compose the payload. • Steganalysis can have a two-sided approach Page 33
  34. 34. • Steganalysis can have a two-sided approach that involves detecting both artifacts and signatures of known steganography applications.All files on a suspect filesystem can be hashed using a hash function and then compared to a hash table of known steganography applications to show that a particular steganography application is, or was, present on the system at some point in time. The second step in the steganalysis process is to search all files on a suspect filesystem for signatures (uniquely identifiable byte patterns) that act as identifiers that are embedded as a result of hiding the information. Page 34
  35. 35. • Difference between Cryptography and Steganography & Watermarking• Cryptography hides the content of the message, but not the existence of the message; steganography & watermarking hide both the contents and existence of the message. Page 35
  36. 36. • Then what is the difference between Steganography and Watermarking?• Steganography performs message hiding such that an attacker cannot detect the presence of the message in the image/video/audio; watermarking hides the message such that an attacker cannot tamper with the message contained within the image/video/audio. Page 36
  37. 37. Applications • Used in modern printers • Allegedly used by terrorists. e.g. It is alleged that Al-Queda used Chaffing to encrypt messages at time of 9/11 and exchanging images via • Alleged use by intelligence services: In 2010, the FBI revealed that the Russian foreign intelligence uses customized steganography software for embedding encrypted text messages inside image files for certain communications with "illegal agents“ stationed abroad. • Digital Watermarking Page 37
  38. 38. The Conclusion • The conclusion is that in this world there are still too many secrets setec astronomy Page 38
  39. 39. Hanky OutIT MEANS: THANK YOU Page 39