Improving the Security of LSB Image Steganography

— Steganography is the technique of hiding secret data (message) within any media such as digital color image. In this paper we will merge steganography process with cryptography process in order to increase the security of the proposed method. The steganography process will based on LSB method, while the cryptography process will based on generating a huge private key and selecting a special function for encryption decryption. The proposed method will be implemented in order to calculate some performance parameters to prove the efficiency of the proposed method.


I. INTRODUCTION
Steganography is the technique of hiding secret information (message) within any media such as digital color image [1-22.The objective of steganography is to hide a secret data within a covering image such a way that others cannot discern the presence of the hidden data.
Hiding secret data (message) into color image requires following elements as shown in figure (1): • The covering color image that will hold the hidden secret message.• The secret message may be plain text, cipher text or any type of data.The stego function to be used to hide and unhide the message.One of the most popular methods used in steganography today is least significant bit (LSB) insertion.Here; the least significant bits of the covering color image are altered so that they form the embedded secret message as shown in table (1).The advantages of LSB are its simplicity to hide the bits of the secret message directly into the LSB plane of covering color image and many techniques use these methods [3].Applying the LSB method does not result in a humanperceptible difference because the changes between the covering and holding images are very small.Therefore, to the human eye, the resulting holding image will look identical to the covering image.This allows high perceptual transparency of LSB as shown in figures ( 2) and (3).The disadvantages of LSB method is that the method is not secure, because it is very easy hack the secret message and extract it by any un-authorized person.

II. MATERIAL
Many authors provided various methods and techniques for data hiding based on LSB method of data hiding.
In [4] the authors proposed a survey on recent achievement of LSB based image steganography and discussed the enhancements done to improve current LSB based steganographic methods.They also proposed two new steganographic techniques.In [5] a new secret data hiding technique was proposed which was based on LSB method with different progression.Experimental results showed that the proposed method is fast and highly efficient as compared to traditional LSB method.In [6] a new method was proposed in which multiple RGB images are embedded into single RGB image using DWT.Proposed system has high embedding capacity and security with minimal changes in stego image.In [7] a very latest approach of binary image steganography was proposed.This technique reduces the distortion on the textures.The proposed method also provides a measurement scheme.The authors concluded that their method has high statistical security with high data hiding capacity.In [8] a new approach based on heuristic genetic algorithm was proposed, which optimally find the appropriate locations in cover image to hide data.Simulation results showed that their method is more efficient than traditional LSB based method.In [9] a new improved version of LSB method was presented, which preserved the histogram and thus prevented the histogram analysis-based attacks.This method also eliminates the embedding of extra bits thus leads to high stego image quality.
In [10] Authors proposed Huffman coding based novel steganographic technique of LSB substitution.This work mainly focuses on high security and embedding capacity and acceptable level of visual quality of stego image.Experimental results demonstrate that proposed scheme has peak signal to noise ratio (PSNR) of 30 dB to 31 dB.
In [11] New steganographic method was proposed and implemented based on bit inversion.Experimental results represented that PSNR value of stego image is improved using this method.
In [12] a comparative analysis of secrete message hiding methods was proposed and it was mentioned that the analyzed methods: Optimum Pixel Adjustment Procedure [13], Inverted Pattern Approach [14], P Method Using Relative Entropy [14], and Pixel Value Differencing (PVD) [15] reduces the distortion caused by the LSB substitution methods.

III. METHOD / ALGORITHM
The proposed method can be implemented applying the following phases: Phase 1: Generating private key.
Here the private key is used for color image encryptiondecryption; it can be generated by performing the following steps: 1) Apply the following formula to generate the private key: This key is very huge and complicated in order to maximize the hacking time and makes it impossible for hacking.2) Save the private key Phase 2: Hiding secret message This phase can be implemented applying the following steps: 1) Get the original covering image.
3) Apply LSB method to insert the message into the covering image.4) Load the private key.5) Extract the used-key from the private key applying the following formula: 6) Encrypt the holding image using a selected stegofunction( XORing the holding image with the usedkey): 7) Save the encrypted image.

Phase 3: Extracting the secret message
This phase can be implemented applying the following steps: 1) Get the encrypted holding image.
3) Load the private key.4) Extract the used-key from the private key applying the following formula: 5) Decrypt the holding encrypted image using the stego-function: 6) Apply LSB method to extract the message into the decrypted holding image.

IV. RESULT
The proposed method was implemented by using the covering image and a secret message 'Ziad A.A.AlQadi' and the results of implementation are shown in figures ( 4) through (7): The proposed method was implemented several time using various images with a fixed message, table (2) shows the calculated performance parameters of this experiment: We can see from table (2) that required total hiding times and total extraction times are very small and they range from 0.2620 to 0.3400 seconds depending on the covering image size.
Another experiment was implemented using various in size messages by fixing the covering image with size equal 983x1300x3 pixels, the results of this experiment are shown in table (3). Figure (8) shows the relationship between the hiding, extractions times and the message size.The covering original image was compared with decrypted one and they are much closed as shown in figure (9), the mean square error (MSE) [12] between them was calculated and it was equal 0.0187 which very small and acceptable, also PSNR [12] was calculated and it was equal 150.6190 which is very high and acceptable.From the obtained results we can raise the following facts: • Color and gray images can be used for steganography.• The used-key is as an image in size, this will enhance the method security.• We can use any image, with different types and size.
• We can hide/extract huge messages without damaging the covering image.• The performance of the proposed method is acceptable.

V. CONCLUSIONS
A simple, secure and highly efficient method of data steganography was proposed, tested and implemented.
The obtained results showed that encrypting-decrypting the holding image increases the method security without losing the method efficiency and without damaging the holding image by concentrating our mind on the advantages of LSB method of steganography and the advantages of the proposed data encryption-decryption methodology.

Fig. 3
Fig 2 Original covering image

Fig 8 .
Fig 8. Hiding and extraction times

TABLE I HIDING
A (BINARY VERSION= 01000001 BINARY)

TABLE II METHOD
PERFORMANCE BY HIDING MESSAGE WITH SIZE=50 CHARACTERS