2. Information “hiding -Introduction
Purpose:
Hiding sensitive information vital or security purposes.
Securing private files and documents.
Hiding information – 3 methods ‘Cryptography’, ‘Steganography’,
‘Watermarking’.
Cryptography Data to be hidden is coded
Several techniques ;sophisticated.
Visually obvious to be encrypted ; appears non-sensical
Watermarking
Applies a copyright label ; prevents illegal use of content.
Improper removal causes degradation of original information.
Steganography
Hiding information by using another information as a cover.
Elements
Cover component ,message component , stego component
3. Steganography -Introduction
What is Steganography?
The word stegano mean cover and graphical mean write. Thus Stegano and graphy both combine together
to make the process in which we hide the important information inside the image using some encoding technique.
This process not only hides the data it also hides the communication which means others will not known whether
the communication is taking place or not.
Types:
Text steganography
Image steganography
Video steganography
Audio steganography
Image steganography is widely used
Images contain redundant information.
Easy to manipulate few pixels without affecting visual data observably.
Slight changes in RGB values undetected by human eye (HVS)- Psychovisual redundancy.
Types : Text in image - image in image.
4. Image steganography
Initially uses in images sent through emails.
Presence detected by huge side of the stego-images.
Various techniques available:
LSB substitution method
Blocking method
Palette modification method
LSB technique can be used for BMP(bitmap) images.
Blocking method – DCT an DWT – used for JPEG images,
Palette based method – used for GIF images.
5. Methods
1. Least Significant Bit(LSB)
Least significant bit (LSB) method is a common, simple approach
to embedding information in a cover file.
In steganography, LSB substitution method is used. I.e. since every
image has three components (RGB).
This pixel information is stored in encoded format in one byte.
The first bits containing this information for every pixel can be
modified to store the hidden text.
6. 2. Blocking Method
In blocking method, blocks of the image are considered and DCT
(discrete cosine transform) is done in order to break them.
Each block is then subdivided into 64 parts (DCT coefficients).
These coefficients are modified i.e. the colour gets modified a
little by storing some text or another image in it.
Embedding the secret data in the carrier image is generally done
for the DCT coefficients that are lower than the chosen threshold
value.
7. 3.Palette modification:
In palette modification, the unused colours in an image’s colour palette are
replaced with colours to represent hidden message.
Palette Modification replaces the unused colours within an image’s colour
palette with colours that represent the hidden message.
8. APPLICATIONS
Steganography is applicable to, but not limited to, the following areas.
1) Secure Private Files and Documents.
2) Hide Password and Encrypted Keys.
3)Transport high private documents over international government.
4) Transmit message/data without revealing the existence of available message.
9. ADVANTAGES
• The secret message does not attract attention to itself as
an object of security.
• Steganography is connected with concealing a secret message is
being sent as well as concealing the content of the message.
• Difficult to detect. Only receiver can detect.
• Provides better security for data sharing
10. LIMITATIONS
• The confidentiality of information is maintained by the algorithms,
and if algorithm are known then this techniques is no use.
• Password leakage may occur and it leads to the unauthorized access of data
