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    Unit 2 Steganography 2.0

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    nihal
    Steganography is the practice of hiding secret messages within other files like images, audio, or video. It works by embedding the secret message into the least significant bits of pixels in an image or by altering slight imperceptible aspects of an audio or video file. Different techniques for image steganography include spatial domain methods, transform domain techniques, and algorithms like least significant bit substitution that replace the binary values of the least significant bit with bits from the hidden message.

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    Unit 2 Steganography 2.0

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    nihal
    12 views16 pages
    Steganography is the practice of hiding secret messages within other files like images, audio, or video. It works by embedding the secret message into the least significant bits of pixels in an image or by altering slight imperceptible aspects of an audio or video file. Different techniques for image steganography include spatial domain methods, transform domain techniques, and algorithms like least significant bit substitution that replace the binary values of the least significant bit with bits from the hidden message.

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    Steganography is the practice of hiding secret messages within other files like images, audio, or video. It works by embedding the secret message into the least significant bits of pixels in an image or by altering slight imperceptible aspects of an audio or video file. Different techniques for image steganography include spatial domain methods, transform domain techniques, and algorithms like least significant bit substitution that replace the binary values of the least significant bit with bits from the hidden message.

    Copyright:

    © All Rights Reserved
    Download as PPTX, PDF, TXT or read online from Scribd
    Download as pptx, pdf, or txt
    12 views16 pages

    Unit 2 Steganography 2.0

    Uploaded by

    nihal
    Steganography is the practice of hiding secret messages within other files like images, audio, or video. It works by embedding the secret message into the least significant bits of pixels in an image or by altering slight imperceptible aspects of an audio or video file. Different techniques for image steganography include spatial domain methods, transform domain techniques, and algorithms like least significant bit substitution that replace the binary values of the least significant bit with bits from the hidden message.

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    © All Rights Reserved
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    Download as pptx, pdf, or txt
    of 16

    Unit 2

    Steganography
    Tripti Misra
    Steganography
    • It is often combined with cryptography in communication.

    • Steganography is still often used for uniqueness and validation purposes, such as
    storing data without it being obvious the data is stored there.

    • For example, almost all modern laser printers now print a series of barely visible
    yellow dots on every page printed. These dots, when interpreted properly, contain a
    variety of meta data about the print job, such as the date and time, printer model,
    and serial numbers.

    • Steganography is the art and practice of communicating using hidden messages,


    often disguised within something else where one would not expect a message to be
    contained in.
    Steganohraphy

    Cover medium: It is an image that holds secret message.


    The Secret message: it is message to be transmitted. It can be plain or
    encrypted text, images or any other data.
    The Stego-key: it is key used to hide the message (May or may not be used).
    Steganography, Cryptography &
    Watermarking
    • Cryptography is about protecting the content of
    messages (their meaning)

    • Steganography is about concealing the existence of


    messages

    • Watermarking is about establishing identity of


    information to prevent unauthorized use
    • They are imperceptible
    • They are inseparable from the works they are embedded in
    • They remain embedded in the work even during transformation
    Watermarking Examples
    • Sending a message to a spy by marking certain letters in a
    newspaper using invisible ink
    • Adding sub-perceptible echo at certain places in an audio
    recording.
    • Embedding a picture of President Andrew Jackson into the
    paper during paper making process.
    Steganalysis
    • Steganalysis is the art of discovering and rendering
    useless such covert messages.
    • Steganalysis involves analysis of the carrier file
    • Simpler steganographic techniques produce some
    discernible change in the file size, statistics or both.
    • These changes can manifest themselves in color
    variations, loss of resolution and other distortions that
    are visible to the human eye.
    • This form of detection requires that you know what the
    original carrier image or file should look like.
    Steganography Types
    • Image Steganography: Taking the cover object as image in steganography is known as image steganography. Generally, in
    this technique pixel intensities are used to hide the information.
    • Network Steganography: When taking cover object as network protocol, such as TCP,UDP, ICMP, IP etc, where protocol is
    used as carrier, is known as network protocol steganography. In the OSI network layer model there exist covert channels
    where steganography can be achieved in unused header bits of TCP/IP fields.
    • Video Steganography: Video Steganography is a technique to hide any kind of files or information into digital video format.
    Video (combination of pictures) is used as carrier for hidden information. Generally discrete cosine transform (DCT) alter
    values (e.g., 8.667 to 9) which is used to hide the information in each of the images in the video, which is not noticeable by
    the human eye. Video steganography uses such as H.264, Mp4, MPEG, AVI or other video formats.
    • Audio Steganography: When taking audio as a carrier for information hiding it is calledaudio steganography. It has become
    very significant medium due to voice over IP (VOIP) popularity. Audio steganography uses digital audio formats such as
    WAVE, MIDI, AVI MPEG or etc for steganography.
    • Text Steganography: General technique in text steganography, such as number of tabs,white spaces, capital letters, just like
    Morse code and etc is used to achieve information hiding
    Image Steganography
    Image Steganography Techniques
    • Spatial Domain Methods: There are many versions of spatial steganography, all directly change some bits in
    the
    image pixel values in hiding data. Least significant bit (LSB)-based steganography is one of the simplest
    techniques
    that hides a secret message in the LSBs of pixel values without introducing many perceptible distortions.
    Changes in
    the value of the LSB are imperceptible for human eyes. Spatial domain techniques are broadly classified into:

    1. Least significant bit (LSB)


    2. Pixel value differencing (PVD)
    3. Edges based data embedding method (EBE)
    4. Random pixel embedding method (RPE)
    5. Mapping pixel to hidden data method
    6. Labeling or connectivity method
    7. Pixel intensity based method
    8. Texture based method
    9. Histogram shifting methods
    Image Steganography Techniques
    • Transform Domain Technique: This is a more complex way of hiding information in an image.
    Various algorithms and transformations are used on the image to hide information in it. The
    process of embedding data in the frequency domain of a signal is much stronger than
    embedding principles that operate in the time domain. Most of the strong steganographic
    systems today operate within the transform domain Transform domain techniques have an
    advantage over spatial domain techniques as they hide information in areas of the image that
    are less exposed to compression, cropping, and image processing.

    1. Discrete Fourier transformation technique (DFT).


    2. Discrete cosine transformation technique (DCT).
    3. Discrete Wavelet transformation technique (DWT).
    4. Lossless or reversible method (DCT)
    5. Embedding in coefficient bits
    Image Steganography Techniques
    • Masking and Filtering: These techniques hide information by marking an image, in the
    same way as to paper watermarks. These techniques embed the information in the more
    significant areas than just hiding it into the noise level. The hidden message is more
    integral to the cover image. Watermarking techniques can be applied without the fear of
    image destruction due to lossy compression as they are more integrated into the image.

    • Distortion Techniques: Distortion techniques need knowledge of the original cover image
    during the decoding process where the decoder functions to check for differences
    between the original cover image and the distorted cover image in order to restore the
    secret message. The encoder adds a sequence of changes to the cover image. So,
    information is described as being stored by signal distortion.
    Least Significant Bit Algorithm
    • The most common and popular method of modern day steganography is to make use
    of LSB of picture’s pixel information.

    • This technique works best when the file is longer than the message file and if image
    is grayscale.

    • When applying LSB techniques to each byte of a 24 bit image, three bits can be
    encoded into each pixel.
    LSB Algorithm
    • If the LSB of the pixel value of cover image C(i,j) is equal to the message bit SM of secret
    massage to be embedded, C(i,j) remain unchanged; if not, set the LSB of C(i, j) to SM.

    • Message embedding Procedure is given below:

    S(i,j) = C(i,j) - 1, if LSB(C(i,j)) = 1 and SM = 0

    S(i,j) = C(i,j) + 1, if LSB(C(i,j)) = 0 and SM = 1


    S(I,j) = C(i,j), if LSB(C(i,j)) = SM
    Where LSB(C(i, j)) stands for the LSB of cover image C(i,j) and “SM” is the next message
    bit to be embedded. S(i,j) is the stego image.
    Example
    • Example:
    We can use images to hide things if we replace the last bit of every color’s byte with a
    bit from the message.
    Message A-01000001

    Image with 3 pixels


    Pixel 1: 11111000 11001001 00000011
    Pixel 2: 11111000 11001001 00000011
    Pixel 3: 11111000 11001001 00000011
    Example contd...
    Now we hide our message in the image.
    Message: 01000001

    Pixel 1: 11111000 11001001 00000010


    Pixel 2: 11111000 11001000 00000010
    Pixel 3: 11111000 11001001 00000011

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