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STEGANOGRAPHY The art and science of hiding communication!!

Firdous Ahmad Khan102/10CSE @ NIT SXR

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TABLE OF CONTENTS

• Introduction

• Different Than Cryptography

• Historical Perspective

• Steganography in Written Text

• Modern Steganography

• Text In Image

• Image in Image

• Audio & Video Steganography

• UV Watermarking

• Network Steganography

• Steganalysis

• Conclusion

• References

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INTRODUCTION

•  Derived from the Greek words steganos (στεγανός) meaning "covered or protected," and graphei (γραφή) meaning "writing." 

• It is the art of hiding stuff in stuff so that others can’t see your stuff.

• Steganography is the practice of hiding data in other data in an effort to keep third parties from knowing that the intended message is even there !

• Encryption's ugly step brother !

• It has art aspects since human judgment is involved.

• Principle : Principle Of Steganography.mp4

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DIFFERENT THAN CRYPTOGRAPHY

• Cryptography is the essence to prepare a message in such a way that unauthorized parties aren’t able to understand it while as Steganography is the essence to embed secret messages within seemingly innocent carriers such that unauthorized parties are unaware of the communication.

• Cryptography provides privacy, Steganography is intended to provide secrecy.

• Steganography– hide, without altering

– obfuscates the fact of communication, not the data

– preventative - deters attacks

• Cryptography– alter, without hiding

– obfuscates the data, not the fact of communication

– curative - defends attacks

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HISTORICAL PERSPECTIVE

• Dates back to 400 BC when Histaeus sent a message, by shaving the head of his most trusted slave, then tattooed a message on the slave's scalp, to his friend Aristagorus, urging revolt against the Persians.

• Demaratus tells Athens of Persia’s attack plans by writing the secret message on a tablet, & covers it with wax.

• Chinese wrote messages on silk and encased them in balls of wax. The wax ball, "la wan," could then be hidden in the messenger.

• A more subtle method, nearly as old, is to use invisible ink( lemon juice, milk, or urine, all of which turn dark when held over a flame).

• Microdots used by Germany in WW2 documents shrunk to the size of a dot & embedded within innocent letters. Inkjet dots smaller than human eyes can see.

Wentworth Miller[Prison Break Serial]

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b. Microdotc. First Publication on Steganography

Also the first book on Steganography was entitled “Steganograpia” written by Johannes Trithemius in the XVI century.

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• Proposed by Girolamo Cardano in XV century.

• Carden grille was a sheet of parchment with apertures for writing text.

• Pricking pin holes above or below the letters in a newspaper or article.

• Used by Nazi Forces in WW2.

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PRISONER’S PROBLEM

• In 1984 Gustavus Simmons formulated this problem.

• Two accomplices are arrested in separate cells & are allowed to communicate via warden who can look into the contents of their communication.

• The prisoners are to agree on an escape plan without raising suspicion of the warden.

• Solution is to create a subliminal channel(communicate secretly in normal looking communication over an insecure channel)

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STEGANOGRAPHY IN WRITTEN TEXT

• Covert text can be embedded in printed matter or in text.

• Embedding can also be by means of altering the appearance of text as

a) Skewing

b) Altering space

c) Offsetting

d) Font color alterations.

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In 2004 it was revealed that several printer manufactures use steganography to hide information about printer serial numbers and the manufacturing code to track counterfeits.Brother, Canon, Dell, Epson, HP, IBM, Konica Minolta, Kyocera, Lanier, Lexmark, Ricoh, Toshiba, Xerox

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• An actual message from German spy “read second letter in each word” (example of NULL CIPHER)

“Apparently neutral's protest is thoroughly discounted and ignored. Isman hard hit. Blockade issue affects pretext for embargo on by-products, ejecting suets and vegetable oils”. Pershing sails from NY June 1• We explore new steganographic and cryptographic algorithms

and techniques throughout the world to produce wide variety and security in the electronic web called the Internet.

Explore The World Wide Web• Use Different fonts to indicate 0/1 of letter encodings(Francis

Bacon Cipher)• Laser printers can adjust spacing of lines and characters by less

than 1/300th of an inch. To hide a zero, leave a standard space, and to hide a one leave 1/300th of an inch more than usual. Varying the spacing over an entire document can hide a short binary message that is undetectable by the human eye. 

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MODERN STEGANOGRAPHY• Hiding one message within another(“container”)

• Most containers are rich media Images, audio, video are very redundant, can be tweaked without affecting human eye/ear

US argued that Al_QAIDA implanted instructions within taped interviews.

• Copyright notices embedded in digital art Prove ownership(Watermarking)

Serial number embedded to prevent replication

Seek infringements on the web using spiders/crawlers

• Digital cameras EXIF(Exchangeable Image File Format) tags Not secretive but hidden from the eye

Embed info such as camera type, date, shutter speed, focal length..

• Similarly, possible to embed messages in invisible part of html pages

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TEXT IN IMAGE (2 METHODS)

• Consider a 8-bit grey scale image One pixel of information is stored using 8 bits.

There are 256 different variations of grey.

• As a simple example of least significant bit(LSB) substitution, imagine "hiding" the character 'G' across the following eight bytes of a carrier file (the least significant bits are underlined):

10010101 00001101 11001001 10010110

00001111 11001011 10011111 00010000

• A 'G' is represented in the American Standard Code for Information Interchange (ASCII) as the binary string 01000111. These eight bits can be "written" to the least significant bit of each of the eight carrier bytes as follows:

10010100 00001101 11001000 10010110

00001110 11001011 10011111 00010001

• In the sample above, only half of the least significant bits were actually changed (shown above in italics). This makes some sense when one set of zeros and ones are being substituted with another set of zeros and ones.

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Advantages• Does not change the size of the file

• Is harder to detect than other steganography techniques

Disadvantages• Normally must use the original program

to hide and reveal data

• If the picture with the hidden information is converted to another format, then the hidden data may be lost

LSB ADVANTAGES AND DISADVANTAGES

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CAN YOU TELL THE DIFFERENCE

Before Encoding:255,0,0FF,00,00

11111111,00000000,00000000

After Encoding “101”:255,0,1FF,00,01

11111111,00000001,00000001

Original

Same file with “I should be able to hold 37 bytes!!!” encoded

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IMAGE IN IMAGE

The Image used for embedding should be 8 times greater than the image which is supposed to be kept hidden.

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AUDIO & VIDEO STEGANORAPHYAUDIO

• Data is hidden by modifying sample data.

• Uncompressed audio formats– WAV (Waveform Audio File Format)

– BWF (Broadcast Wave Format)

– MBWF (Multichannel Broadcast Wave Format)

• Compressed audio formats

Lossy

• MP3

• Advanced Audio Coding (AAC)

Lossless

• Free Lossless Audio Codec (FLAC)

• Direct Stream Transfer (DST)

VIDEO

• Coding still frames - spatial or frequency

• data encoded during refresh closed captioning

• visible watermarking used by most networks (logo at bottom-

right)

Example : Audio Steganography.mp4

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UV WATERMARKING

Spatial domain watermarking• bit flipping• color separation

Frequency domain watermarking• embed signal in select frequency bands (e.g. high frequency areas)

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NETWORK STEGANOGRAPHY• Network Steganography

Information hiding techniques which can be utilized to exchange steganograms in telecommunication networks.

Can be Intra-protocol or Inter-protocol

unused bits in packet headers

IP(Type of service, Flags, fragment offset, etc.)

TCP(Sequence Number)

• LACK(Lost Audio Packet Steganography) Hide information in packet delay.

• HICCUPS (Hidden Communication System for Corrupted Networks) Disguise information as natural “distortion” or noise.

• Operating System unused memory

slack space(Fragmentation issue)

unallocated space

hidden partition

normally used to hide data from investigators

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STEGANOGRAPHY VS WATERMARKING

Goal of steganography• Intruder cannot detect a message

• Primarily 1:1 communication

Goal of Watermarking• Intruder cannot remove or replace the message

• Primarily 1:* communication

• Example : Watermarks.mp4

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STEGANALYSIS

• The art and science of steganalysis is intended to detect or estimate hidden information based on observing some data transfer.

• In some cases, just being caught sending a message can bring suspicion, or give information to the 3rd party

• Why is this person hiding something?

• Why all the communication right now?

• Steganalysis techniques can be classified in a similar way as cryptanalysis methods, largely based on how much prior information is known

• Steganography-only attack: The steganography medium is the only item available for analysis.

• Known-carrier attack: The carrier and steganography media are both available for analysis.

• Known-message attack: The hidden message is known.

• Chosen-steganography attack: The steganography medium and algorithm are both known.

• Chosen-message attack: A known message and steganography algorithm are used to create steganography media for future analysis and comparison.

• Known-steganography attack: The carrier and steganography medium, as well as the steganography algorithm, are known discipline with few articles appearing before the late 1990s.

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STEGANOGRAPHY TOOLS

• Steganos

• S-Tools (GIF, BMP)

• StegHide (WAV, BMP)

• Invisible Secrets (JPEG)

• OpenPuff(BMP, JPEG, PNG)

• Camouflage

• MP3Stego(Open Source tool for audio)

• OpenStego (Open Source tool for images)

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QUICK RECAP

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CONCLUSION

• Steganography & Steganalysis are still at an early stage of research.

• Although in principle secure schemes exist, practical ones with reasonable capacity are known.

• Notion for security & capacity for steganography needs to be investigated.

• Since it obvious that no system of data hiding is totally immune to attacks. However, steganography has its place in security. It in no way can replace cryptography, but is intended to supplement it. Its application in watermarking for use in detection of unauthorized, illegally copied material is continually being realized and developed.

• The growing number of communication protocols, services and computing environments offers almost unlimited opportunities for displaying a whole spectrum of steganographic methods.

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REFERENCES

• http://www.petitcolas.net/fabien/steganography/history.html

• http://en.wikipedia.org/wiki/Steganography

• http://www.fbi.gov/about-us/lab/forensic-sciencecommunications/fsc/july2004/research/2004_03_research01.htm

• http://stegano.net/tutorial/steg-history.html

• http://www.strangehorizons.com/2001/20011008/steganography.shtml

• http://www.docstoc.com/docs/53840814/Steganography-and-History-of-Cryptography

• http://www.securitytube.net/video/905

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THANK YOU