Steganography In Images Using Pixel Replacement Technique Computer Science Essay

In this age of cosmopolitan electronic connectivity, of viruses and hackers, of electronic eavesdropping and electronic fraud, there is so no clip at which security of information does non count. The explosive growing of computing machine systems and their interconnectednesss via webs has increased the dependence on the information stored and communicating utilizing these systems. This has led to a heightened consciousness of the demand to protect the information transmitted.

Therefore the field of cryptanalysis has got more attending today. More and more complex techniques for coding the information are proposed every now and so. Some advanced encoding algorithms like RSA, DES ; AES etc. which are highly difficult to check hold been developed. But, as usual, when a little measure is made to better the security, more work is done in the opposite way by the hackers to interrupt it. Thus they are able to assail most of these algorithms and that excessively, successfully. Even complex algorithms like RSA are no exclusion to this.

So, to lead on the hackers, people have started to follow a technique called ‘Steganography ‘ . It is non an wholly new technique and has been in the pattern from ancient times. In this method, the information is hidden behind unsuspicious objects like images, sound, picture etc. so that people can non even acknowledge that there is a 2nd message behind the object. Images are normally used in this technique.

In this paper, we have proposed a technique for concealing informations in secret behind images. The bing techniques for image Steganography have some serious drawbacks and we have tried to get the better of those with ours. Here, the pels in the images are replaced with the new 1s, which are about indistinguishable to the old 1s, in a mode that can be used to recover back the hidden informations. We have implemented this technique practically and found the consequences fulfilling.

In today ‘s universe of increased security concern in the Internet due to choping, strong cryptanalysis techniques are required. But, unluckily, most of the cryptanalysis techniques have become vulnerable to assail by the snoopers. This applies to some of the advanced encoding methods excessively. So, the demand of the hr is to happen new methods for maintaining the information secret. One such method normally proposed presents is ‘Steganography ‘ .

1 Steganography Defined

Cryptography is the art and scientific discipline of pass oning in a manner which hides the being of the communicating. In contrast to cryptanalysis, where the “ enemy ” is allowed to observe, stop and modify messages without being able to go against certain security premises guaranteed by a cryptosystem, “ the end of cryptography is to conceal messages inside other harmless messages in a manner that does non let any enemy to even observe that there is a 2nd secret message nowadays. ”

2 Steganography In Images

In kernel, image cryptography is about working the limited powers of the human ocular system. Within ground, any field text, ciphertext, other images, or anything that can be embedded in a spot watercourse can be hidden in an image. The common methods followed for concealing informations in images are the ‘Least Significant Bit ( LSB ) Insertion ‘ technique in which the LSB of the pel values are replaced with the informations to be encoded in binary signifier, the ‘Masking Technique ‘ in which the original spots are masked with informations spots and the ‘Filtering Technique ‘ in which certain transmutations are done on the image to conceal informations. The last two techniques conceal informations by taging an image in a mode similar to paper water lines But, there are some drawbacks with these methods which hinders their usage.

3 Drawbacks In The Current Techniques

Highly apt to onslaughts like Image Manipulation techniques where the pels will be scanned for a possible relation which will be used to follow out the existent characters.

Merely 24 spot messages are suited and 8 spot images are to be used at great hazard.

Extreme Care needs to be taken in the choice of the screen image, so that alterations to the informations will non be seeable in the stego-image.

Normally known images, such as celebrated pictures must be avoided.

4 The Pixel Replacement Techniuque

Because of the drawbacks in the presently followed techniques, we propose a new technique for concealing informations in images. Here, we replace the bing pels in the image with the new 1s in such a manner that no difference is seeable between the steganographed and the original image.

The Algorithm

Encoding

The Algorithm used for encoding in this technique can be described with the undermentioned stairss:

Get the Image, Message to be hidden and the Password.

Encrypt the message and the watchword.

Move some rows below the first row in the image and repair a mention place near the left border for uneven characters and near the right for even characters.

For each character in the original informations do

happen a place matching to that character

hunt the surrounding pels and happen a pixel value closer to all of them

replace the current pel and the mention pel with this value

move to the following row

Put a pixel value as a threshold.

Repeat stairss 4 and 5 for the Password from the underside of the image.

Decoding

The Algorithm for recovering the original message from the steganographed image follows this sequence:

Get the Image and the Password.

Move to the bottom row in the image where watchword concealment starts.

Find the value of the mention pel.

Search the full row for the same pel value.

Find the place of that pel and decrypt the character.

Repeat stairss 3 thro 5 till the threshold is reached.

Concatenate all the characters found so far ( Actual Password ) .

If the found watchword does non fit the given watchword travel to step 11.

Move to the top row in which the first character of original informations was stored.

Repeat the sequence followed in stairss 3 to 7 to acquire the original message.

Expose the consequence.

5 FLOW DIAGRAM

The flow diagram of our propsed system may be shown as:

Encoding

Decoding

6 Execution

With the algorithm described in brief, allow us depict the pixel replacing technique in item. First, we shall see how the original message and the watchword are hidden into the image and so we ‘ll discourse how to recover message for the authorised individual who knows the right watchword.

Coding the Message & A ; Password

First, the original message and the watchword are got from the user. Then, they are encrypted utilizing any of the encoding algorithms like RSA, DES etc.This encoding measure is an extra safety characteristic added to the technique to guarantee maximal safety.Then, this encrypted message is fed as the input to the following measure.

Choosing a place to conceal the character

The existent procedure of cryptography starts here. The Image is scanned from the top row – wise. First few rows are omitted and a suited row is reached. The message is split into single characters. The undermentioned procedure is repeated for all the characters in the message. A place for concealing the character is chosen harmonizing to some relation with that character. The relation can be something like the ASCII value of the character, the order of occurence of that character in the Alphabetical or Reverse order if it is an alphabet etc.

For illustration, the place of the character ‘R ‘ can be chosen as:

ASCII Value of ‘R ‘ = 82,

So, place = 82 – 50 = 32.

( merely eg. any value alternatively of 50 can be used )

Finding a Suitable Coloring material

Once a place is chosen, the values of all the pels environing the pel in that place are found. Since this place is normally non near the border of the image, there will be 8 pels environing it. A pixel value, i.e. , a coloring material, is chosen so that it does non differ much from those of the 8 pels. This is the most hard measure in the whole procedure. The value will differ merely by a little value. Such a little alteration in the coloring material will be indiscernible to the users.

Replacing the pels

Now, with the coloring material to be replaced being found, it ‘s clip to replace the pels with the new coloring material. A place near to the left side of the row is fixed as the mention place for the uneven numbered character i.e. , the 1st, 3rd,5th character and so on. Similarly, for the even numbered characters, a place near to the right side of the row is selected as the mention place. These mention places are the same for all the characters. When the mention place is chosen, the pel in that place is replaced with the new coloring material. Then, the pel in the already found place for the character ( in our eg. , this is 32 ) is besides replaced with the new coloring material.

Example

Let us see a sample image whose pels are replaced in this manner. This can be explained by the undermentioned figure.fig ( 1 )

For the interest of account, the pels are shown clearly in this figure. But, in existent state of affairss, these will non be seeable at all because the coloring material chosen for replacement is so close to the original coloring material that can non be found by the human oculus but still can be found out by the computer.The above mentioned stairss of happening a suited coloring material and replacing the pels is continued for all the characters in the encrypted message.

Puting a Threshold

The concluding measure in concealing the message is to put a threshold pel in a fixed place to bespeak the terminal of the encrypted message. This is indispensable for decrypting the message from the image. Otherwise, we can non happen the terminal of the message.

Hiding the Password

The same stairss of chosing the coloring material, replacing the pels and puting a threshold are repeated for concealing the watchword but the lone difference is that the image is scanned row – wise from the last row alternatively of from the first row.

Recovering the Message

The procedure of recovering the original message from the steganographed image is similar to that of the concealment procedure except in the contrary order. First, the watchword is got from the user. The image is scanned from the last row and the row in which the watchword concealment started is reached. The mention pel value is found and the place of that coloring material in that row is noted. Then, once more the relation used antecedently for happening the place is used to acquire the original character. This can be explained as:

If the place is 32, so

32 + 50 = 82,

The character of ASCII value 82 is ‘R ‘ .

Similarly, the other characters are found till the threshold is reached and all of them are concatenated to acquire the original watchword. Now, the given watchword and the original are checked and if they match, so farther procedures are done, otherwise, an mistake message is diaplayed.

If the watchword lucifers, so the image is scanned from the top and the get downing row from where the information concealment started is reached. The same stairss of happening the mention pel and the place of the other pel are repeated once more till the threshold. Then, all the characters are joined and the original message is displayed.

7 Practical Execution

We have completed a undertaking utilizing this pixel replacing technique utilizing Visual Basic 6.0. Assorted types of images like JPEG, BMP, GIF etc are used as beginning image and the consequences are noted. The consequences are assuring. Let us see one of the consequences here which uses a BMP image:

An illustration of the Pixel Replacement technique

realized utilizing Visual Basic

*****Original Image*****

***Contaminated Image***

As seen from this illustration, there are no large alterations seeable between the existent image and the 1 in which information is hidden. Therefore, our proposed technique can be an utile one for concealing messages in images.

8 Advantages Of Our Technique

Cost of checking the concealed message is highly high.

The informations can non be easy decoded without the key utilizing Image Manipulation techniques.

Any type of image, 8 or 24 spots can be used.

There is no addition in the size of the image due to informations in it.

There are no restraints on the pick of the image.

Wraping Up

To get the better of the drawbacks in the bing cryptanalysis and cryptography techniques, we have proposed a new technique for concealing informations in images. Our technique is less prone to onslaughts and since the information is strongly encrypted and the cost of recovering it by unauthorised individuals is extremly high. Since the pels are replaced with about indistinguishable pels, it is hard to even place that there is a 2nd message hidden. So, we hope that our technique will be used widely in the hereafter.

Fig ( 1 ) :

Image Before ( B ) Image After

Replacement Replacement