digital steganography
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The document discusses steganography, which is the practice of hiding secret messages within other harmless messages or files. It provides an introduction and history of steganography, outlines the differences between steganography and cryptography, describes how to perform steganography using different media like images and audio, discusses digital watermarking techniques, and notes advantages and disadvantages of steganography.
digital steganography
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- 2. OUTLINES o Introduction o History o Steganography V/S Cryptography o Steps Involved In Steganography o Stegnography In Various Media o Digital Watermarking o Watermarking V/S Steganography o Steganalysis o Advantage & Disadvantage 2 2/25/2014
- 3. Introduction o Greek Words: STEGANOS – “Covered” GRAPHIE – “Writing” o Advance security is not maintained by the password protection but it is gained by hiding the existence of the data, which can only be done by Steganography o Steganography is the art and science of writing hidden messages in such a way that no one apart from the intended recipient knows of the existence of the message o This can be achieve by concealing the existence of information within seemingly harmless carriers or cover o Carrier: text, image, video, audio, etc. 3 2/25/2014
- 4. History o Greeks used it writing message on some material and later covering it with wax, tattooing messages on bald head, later growing hair to cover it up. o In World War II invisible inks were used to write messages in between the lines of normal text message. o Currently, cryptography and steganography are used to hide and send the secret data. 4 2/25/2014
- 5. Steganography V/S Cryptography o Cryptography hides the contents of a secret message from a malicious people, whereas Steganography even conceals the existence of the message. o In cryptography, the structure of a message is scrambled to make it meaningless and unintelligible unless the decryption key is available. o Steganography does not alter the structure of the secret message, but hides it inside a cover-image so it cannot be seen. 5 2/25/2014
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- 7. Steps involved in Digital Steganography 7 2/25/2014
- 8. Digital Steganography Under Various Media o Steganography In Text/Documents o Steganography In Images o Steganography In Audio 8 2/25/2014
- 9. Steganography In Text/Documents It involves three types of coding: o Line-Shift Coding : Here, text lines are vertically shifted to encode the document uniquely. o Word-Shift Coding : The code words are coded into document by shifting the horizontal locations of words within text lines, while maintaining a natural spacing appearance. o Feature Coding : In feature coding, certain text features are altered, or not altered, depending on the codeword. 9 2/25/2014
- 10. Hiding a Message inside Text Partially effective o randoM capitalosis is a rarE disEase ofTen contrAcTed by careless inTernet users. tHis sad illnEss causes the aFfected peRsON To randomly capitalize letters in a bOdy oF texT. Please do not confuse this disease witH a blatant attEmpt aT steganogRAPhy. Reveals: MEET AT THE FRONT OF THE TRAP 10 2/25/2014
- 11. Steganography In Images o Image Compression: Image compression offers a solution to large image files. Two kinds of image compression are lossless and lossy compression. Both methods save storage space but have differing effects on any uncompressed hidden data in the image. o “Lossy” JPEG(Joint Photographic Experts Group) format files, offers high compression, but may not maintain the original image's integrity. Hence it is called “lossy”. “Lossless” compression maintains the original image data exactly, It is thus more favored by steganographic techniques. Eg: (BMP ),(GIF) Formats. 11 2/25/2014
- 12. Image Based Techniques Least significant Bit Masking And Filtering 12 2/25/2014
- 13. L.S.B Steganography o Replacing least-significant-bits (LSBs) of digital data with message bits. 110010 00 Embedding Extracting o Embedding random message bits in LSBs will not cause any discernible difference from the cover-signals. o Easy to implement, High payloads. o 13 Simple, but susceptible to lossy compression and image 2/25/2014 manipulation.
- 14. L.S.B Uses o Storing passwords and/or other confidential information o Covert communication of sensitive data o Speculated uses in terrorist activities o Being widely used to hide and/or transfer illegal content 14 2/25/2014
- 15. WATERMARKING o A watermark is a form, image or text that is impressed onto paper, which provides evidence of its authenticity. o A distinguishing mark impressed on paper during manufacture; visible when paper is held up to the light. o EXAMPLEThe presence of specific patterns in currency notes which are visible only when the note is held to light is a well known example for watermark. Courtesy of Blue Spike, Inc. 15 2/25/2014
- 16. DIGITAL WATERMARKING • Digital watermarking is an extension watermarking concept in the digital world. of • A digital watermark is a pattern of bits inserted into a digital image, audio or video file that identifies the file's copyright information (author, rights, etc.). 16 2/25/2014
- 17. STEGANOGRAPHY V/S WATERMARKING The main goal of steganography is to hide a message m in some audio or video (cover) data d, to obtain new data d', practically indistinguishable from d, by people, in such a way that an eavesdropper cannot detect the presence of m in d'. 17 The main goal of watermarking is to hide a message m in some audio or video (cover) data d, to obtain new data d', practically indistinguishable from d, by people, in such a way that an eavesdropper cannot remove or replace m in d'. 2/25/2014
- 18. Importance of Digital Watermarking o As seen above in Fig, Alice creates an original image and watermarks it before passing it to Bob. If Bob claims the image and sells copies to other people Alice can extract her watermark from the image proving her copyright to it. o The caveat here is that Alice will only be able to prove 18 her copyright of the image if Bob hasn’t managed to modify the image such that the watermark is damaged enough to be undetectable or added his own watermark 2/25/2014 such that it is impossible to discover which watermark
- 19. THE OVER ALL PROCESS 19 2/25/2014
- 20. Visible Watermarking Visible watermark is a translucent overlaid into an image and is visible to the viewer. Visible watermarking is used to indicate ownership and for copyright protection. MAHESH Watermark 20 Original Image Watermarked Image2/25/2014
- 21. Invisible watermark o Invisible watermark is embedded into the data in such a way that the changes made to the pixel values are perceptually not noticed. Invisible watermark is used as evidence of ownership and to detect misappropriated images. Original Image 21 Watermarked Image 2/25/2014
- 22. Steganography In Audio Phase coding Echo Data Hiding 22 2/25/2014
- 23. PHASE CODING: Phase coding relies on the fact that the phase components of sound are not as perceptible to the human ear as noise is. Rather than introducing perturbations, the technique encodes the message bits as phase shifts in the phase spectrum of a digital signal, achieving an inaudible encoding . ECHO-HIDING: In echo hiding, information is embedded in a sound file by introducing an echo into the discrete signal. Like the spread spectrum method, it too provides advantages in that it allows for a high data transmission rate and provides superior robustness when compared to the noise inducing methods. 23 2/25/2014
- 24. ADVANTAGE & DISADVANTAGE ADVANTAGES : Difficult to detect and Only receiver can detect It can be done faster with large no. of softwares Provides better security for sharing data in LAN, MAN & WAN DISADVANTAGES: The confidentiality of information is maintained by the algorithms, and if the algorithms are known then this technique is of no use Password leakage may occur and it leads to the unauthorized access of data. If this technique is gone in the wrong hands like hackers can be very much dangerous for 24 all 2/25/2014
- 25. Detecting Steganography : • The art of detecting Steganography is referred to as Steganalysis. • Steganalysis does not deal with trying to decrypt the hidden information inside of a file, just discovering it. • It is mainly done with comparing the encrypted file with the original copy. 25 2/25/2014
- 26. REFERENCES http://en.wikipedia.org/wiki/Steganography8 http://computer.howstuffworks.com/file-compression3.htm http://www.math.ucsd.edu/~crypto/Projects/MaxWeiss/steg anography.pdf http://www.sans.org/reading_room/whitepapers/covert/steg anography-matters-post-911-world_676 http://www.scribd.com/doc/49683406/1/Steganography-vs- Cryptography 26 2/25/2014
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