Steganography is the process of hiding a secret message within a larger one in such a way that someone cannot know the presence or contents of the hidden message. Although related, Steganography is not to be confused with Encryption, which is the process of making a message unintelligible—Steganography attempts to hide the existence of communication.
The main advantage of steganography algorithm is because of its simple security mechanism. Because the steganographic message is integrated invisibly and covered inside other harmless sources, it is very difficult to detect the message without knowing
the existence and the appropriate encoding scheme .
Proposed Algorithm
The algorithm is more dedicated towards the algorithm proposed by Rosziati Ibrahim and Teoh Suk Kuan in their Research Paper published on February 25, 2011.
Encoding Algorithm
Firstly, the secret message that is extracted is compressed as the contents in the compressed string will significantly hard to detect and read, furthermore it reduces the size of string.
Secondly, the compressed string is encrypted with the secret key.
Finally, encoding the encrypted message in the image. It uses LSB steganographic embedding to encode data into an image. Once the message is encoded the process stops.
LSB(Least Significant Bit) Embedding
The LSB is the lowest significant bit in the byte value of the image pixel.
The LSB based image steganography embeds the secret in the least significant bits of pixel values of the cover image (CVR).
The concept of LSB Embedding is simple. It exploits the fact that the level of precision in many image formats is far greater than that perceivable by average human vision. Therefore, an altered image with slight variations in its colors will be indistinguishable from the original by a human being, just by looking at it. In conventional LSB technique, which requires eight bytes of pixels to store 1byte of secret data but in proposed LSB technique, just four bytes of pixels are sufficient to hold one message byte. Rest of the bits in the pixels remains the same.
Following shows the bit level interpretation of the algorithm :
Decoding Algorithm
Firstly, decode the message from the encrypted image using LSB decoding.
Secondly, decrypt the compressed message from the decoded message using the secret key.
Finally, decompress the message to get the original compressed message.
Consider the following encoding, it is totally undetectable by human eyes.
Usage
Add it in your root build.gradle at the end of repositories:
Note : By default a ProgressDialog will appear in the process of text encoding.
Override Methods
OnStartTextEncoding() : In this method you can whatever by the start of text encoding process.
@OverridepublicvoidonStartTextEncoding() {
//Whatever you want to do at the start of text encoding
}
onCompleteTextEncoding() : After the completion of text encoding, this method is called and gives result.
@OverridepublicvoidonCompleteTextEncoding(ImageSteganographyresult) {
//After the completion of text encoding.//result object is instantiated this.result = result;
if (result != null && result.isEncoded()){
//encrypted image bitmap is extracted from result objectencoded_image = result.getEncrypted_image();
//set text and image to the UI component.textView.setText("Encoded");
imageView.setImageBitmap(encoded_image);
}
How to decode message from an image ?
Note : Your Activity class should implements TextDecodingCallback interface and also contains its override methods.
Note : By default a ProgressDialog will appear in the process of text decoding.
Override Methods
OnStartTextDecoding() : In this method you can whatever by the start of text decoding process.
@OverridepublicvoidonStartTextDecoding() {
//Whatever you want to do at the start of text encoding
}
onCompleteTextDecoding() : After the completion of text decoding, this method is called and gives result.
@OverridepublicvoidonCompleteTextEncoding(ImageSteganographyresult) {
//After the completion of text encoding.//result object is instantiated this.result = result;
if (result != null){
/* If result.isDecoded() is false, it means no Message was found in the image. */if (!result.isDecoded())
textView.setText("No message found");
else{
/* If result.isSecretKeyWrong() is true, it means that secret key provided is wrong. */if (!result.isSecretKeyWrong()){
//set the message to the UI component.textView.setText("Decoded");
message.setText("" + result.getMessage());
}
else {
textView.setText("Wrong secret key");
}
}
}
else {
//If result is null it means that bitmap is nulltextView.setText("Select Image First");
}
}
Documentation
ImageSteganography Class
Java attribute
Java set methods
Description
Default Value
Message
setMessage(...) , getMessage()
Set the value of message, Get the value of message.
Null
Secret_Key
setSecret_key(...)
Set the value of secret key.
Null
Image
setImage(...)
Set the value of image.
Null
Encoded_Image
getEncoded_image()
Get the value of encoded image after text encoding.
Null
Encoded
isEncoded()
Check that the encoding is over or not
false
Decoded
isDecoded()
Check that the decoding is over or not.
false
SecretKeyWrong
isSecretKeyWrong()
Check that the secret key provided was right or wrong but after decoding was done.
true
Class Domain Diagram
Example App
There are two options Encode and Decode. In the encode section you can hide a secret message into an image without making any noticeable changes. In the decode section you can extract the message from the encoded image by inserting the correct key.
Note - After pressing the Save button, both the original and encoded images are saved at the location Android/data/com.ayush.steganography/files/Documents/<UUID>/
Encode
Decode
Want to contribute !
This is the well documented library. I have documented each and every method that I have used, so have a good read to the code and suggest some changes and new feature to be added in the library.
Feel free to open an issue.
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