Steganography in images

STEGANOGRAPHY IN IMAGES

NIKHIL TRIPATHI12MCMB10M.Tech (IT)

OVERVIEWoSteganography DefinedoExamples in HistoryoDigital ApproachesoReasons For Using Digital ImagesoImage AttributesoPopular Techniques That Use ImagesoSteganalysisoAdvancements in image steganographyoTechnical limitations

STEGANOGRAPHY DEFINED

oGreek for “covered writing”.

o“The art and science of writing hidden messages in such a way that no one apart from the intended recipient even knows that a message has been sent.”

EXAMPLES IN HISTORY

oTattoos on shaved headsoWax-covered tabletsoInvisible Inks - milk, fruit juice

STEGANOGRAPHY V/S CRYPTOGRAPHY

oSteganography involves the hiding of the data while Cryptography involves the encryption and decryption of data.

oSteganalysis involves finding out whether there is really a hidden message or not while Cryptanalysis involves breaking of the encrypted into decrypted message.

STEGANOGRAPHY with CRYPTOGRAPHY

oVery very strong when combined.

oA message sent in secret (steganography) in an encrypted form (cryptography) is much more secure than a "plain text" message sent by secret means or a clearly sent encrypted message.

DIGITAL APPROACHES

oToday, it often exists within digital formats.oIt makes use of seemingly innocent cover files such as text, audio, and image files.oThe embedded message may be anything that can be encoded in binary.

REASONS FOR USING DIGITAL

IMAGESoIt is the most widely used medium being used today.oTakes advantage of our limited visual perception of colors.oThis field is expected to continually grow as computer graphics power also grows.oMany programs are available to apply steganography.

IMAGE ATTRIBUTES

oDigital images are made up of pixels.o8-bit and 24-bit images are common.oThe larger the image size, the more information you can hide. However, larger images may require compression to avoid detection.

IMAGE-BASED TECHNIQUES

oLeast Significant Bit InsertionoMasking and Filtering

LSB INSERTIONoReplaces least significant bits with the message to be encoded.oMost popular technique when dealing with images.oSimple, but susceptible to lossy compression and image manipulation.

LSB - ExampleA sample raster data for 3 pixels (9 bytes)may be:

00100111 11101001 1100100000100111 11001000 1110100111001000 00100111 11101011

Inserting the binaryvalue for

A (10000001)

changes 4 bits

00100111 11101000 1100100000100110 11001000 1110100011001000 00100110 11101011

LSB Continued…

oBest to use a grayscale palette or one with gradual changes in shades.oOtherwise, it is best to use images with “noisy areas” – areas with ample color variation.

LSB - Uses

oStoring passwords and/or other confidential information.oCovert communication of sensitive data.

oSpeculated uses in terrorist activities.oBeing widely used to hide and/or transfer illegal content.

MASKING & FILTERING

oMasks secret data over the original data by changing the luminance of particular areas.oDuring masking, it embed the message within significant bits of the cover image.oNot susceptible to lossy techniques because image manipulation does not affect the secret message.

MASKING & FILTERING - Uses

oDigital Watermarking – provides identification pertaining to the owner; i.e. license or copyright information.

o Fingerprinting – provides identification of the user; used to identify and track illegal use of content.

Visible Watermark - Example

STEGANALYSISFive classes of steganalysis: o Stego-onlyo Known-covero Known-messageo Chosen-stego ando Chosen-message

ADVANCEMENTSoUse of steganography for malwares to embed it in crafted HTML and JPEG files.e.g. Duqu worm (2011)oAccording to recent report(30th Jan, 2012), it will be used in android applications to send premium rates messages.oSelecting multiplayers’ games to use as a covert channel.oUse of private chat rooms as a carrier.oResearch are being done to practice steganography using a key not by using a method.

TECHNICAL CHALLENGES

Limitations due to these three properties which work in opposition to each other:-

oCAPACITY of the cover object.oUNDETECTABILITY of the stego-object.oROBUSTNESS of the stego-object.oStrength often depends on attackers not knowing how data could be hidden.

SUMMARYoSteganography as a whole has existed in many forms throughout much of history.oLossless compression of images with a great deal of color variation work best as a cover image to embed a message.oSteganography can be used as beneficial tool for privacy.oSteganography will work best if combined with cryptography.

REFERENCEShttp://www.youtube.com/watch?v=O

OY-lbDEmNM for techniques of steganographyCERIAS Steganography by John Oritz youtube videos.http://www.garykessler.net/library/st

eganography.htmlhttp://en.wikipedia.org/wiki/Digital_w

atermarkinghttp://www.youtube.com/watch?v=C

0T1MbrST5U for watermarking techniques.http://stegano.net

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