An Improved LSB Algorithm For Image Steganography Based On Combination Of Steganography And Cryptography (ST_CR-LSB)

With the rapid development in digital network,digital libraries,information technology,and particularly World Wide Web services~we are often forced to send information that may be very important and confidential through the Internet.However,data transmission has been repeatedly faced the issue of intrusions.As we know,the security problem has become one of the exceedingly significant problems for data transmission.Steganography offers an ideal solution to this issue.Steganography is the art and science of hiding confidential data inside other data called the cover file.This cover may be a text,image,audio or video.The most commonly used cover is the image,as large quantities of images present on the Internet.Recently,several steganography methods have been introduced and developed to ensure the transmission of data in a secured way.However,some of those methods,such as the Least Significant Bit(LSB)technique have certain limitations.In this work,we propose a new algorithm called ST_CR-LSB to develop LSB steganography method using MATLAB program language.The proposed ST_CR-LSB is a solution for the low security and capacity limitations of the traditional used LSB techniques.In addition,Lempel Ziv Welch(LZW)algorithm is used,which is a simple and lossless compression algorithm.LZW is applied effectively to minimize the magnitude of the confidential message where the dictionary table is not needed during the decompression.In our algorithm,first,the confidential message is encoded and compressed utilizing LZW to reduce the magnitude of the confidential message.This process increases the hidden capacity and enhances the quality of stage Peak Signal to Noise Ratio(PSNR).Then,the secret message and the cover image are both divided into blocks of nxn bits.After that,encryption is done between the message blocks and the image blocks.Finally,we obtain an optimal block and a key.This process accomplishes two objectivesIncrease the security and robustness,due to the new encryption process is used before embedding.Increase the quality of stego image.At the end,the optimal blocks are embedded inside the cover image.In addition,all keys are collated into an array,then this array is embedded into the cover image.The password is simultaneously generated,which is exactly the array's address in the cover image.The proposed technique is compared with other traditional steganographic technique in terms of Mean Square Error(MSE),Peak Signal to Noise Ratio(PSNR)and embedding capacity.From the simulation results,it is inferred that the proposed steganographic method has improved the visual quality of stego image,and shows better robustness compared to the traditional LSB.