Steganography and Cryptography Approaches Combined using Medical Digital Images

- The growth in medical field has led to the transformation of the data from papers into the digital form. As the medical field is moving towards the digital world, security of the medical information/data has become a major concern. The patient information, patient disease diagnosis, etc. are all being stored in the digital images. To make the treatment fast and accurate the digital images are being introduced. This research is about how the data is embedded in the medical scanned images through the combined approach using both cryptography and steganography. The patient information and diagnosis by doctor both serve as the confidential information and hence is treated as secret data. The proposed algorithm attempts to keep this secret data secure and at the same time, make the patient’s treatment accurate and fast.


INTRODUCTION
Steganography is the science and art of data hidden within data. In Steganography the data is hidden in the image in such a way that only the designated recipient knows about the presence of the hidden message. The process is accomplished by hiding one data in another to conceal whether there is any communication. The steganography used various mediums to hide the data, the simplest is the text but the frequently used is the steganography on image. The steganography is broadly divided into three types they are text, image, and audio/video. The information is hidden purely in images in image steganography. Watermarking and fingerprinting are the two other technologies closely related to the steganography. Steganography is somewhat different from cryptography. Steganography is considered as the dark or first cousin of the cryptography. The cryptography provides privacy to the data on the other hand steganography is used to hide the data and provide secrecy. Cryptography is basically used for the security process. The cryptography is a process which is used to provide the secure communication between two mediums in a form that is not understood by normal human being. This is also used to hide data and to communicate over the internet which is not trusted and the data needs to be saved from various third parties. In cryptography we encrypt the data but in case of steganography we hide the data. Steganography is also considered as true secrecy in the field of security. So, steganography is considered more secure than cryptography. Steganography was widely used in ancient times. For example, the hidden message may be written with invisible ink between the visible lines of the private data or letter. Steganography in modern times uses digital media whether it is in image or audio/video file. Digital media is used to hide messages or data on the internet or in the private communication. Today internet has become mandatory in normal life, but it also has concern for security. So, this security concern has being tackled using steganography. To evaluate the performance of two steganography algorithms (Spatial domain algorithm and Transform domain algorithm) various evaluation parameters are identified based on the quality of these two algorithms and listed below. [1]  Security: A steganography algorithm is said to be secure if any test performed on it results in no difference between the stego image and the original image.  Capacity: The capacity of an algorithm can be described as the amount of the data that can be effectively hidden in the present or the selected cover medium by the Steganography algorithm.  Domain of Embedding: The domain of embedding plays a vital role to determine the overall performance of the Steganography algorithm. Example: In case of spatial domain algorithm, it often offers high capacity of data embedding but it falls down to statistical steganalysis.  Image supported: There are large number of image formats available. This parameter shows which type of image format is suitable for which Steganography algorithm.  Time complexity: Time complexity plays a vital role in the Steganography. The time complexity of an algorithm is used for judging the performance of an algorithm for hiding or embedding data into large images and also the implementation of the algorithm in the smaller devices such as mobile device etc.  Imperceptibility: This parameter basically deals with the image quality. In this image quality should not be compromised by the hidden or embedded data present.  Independent of file format: There are number of file formats and the most powerful and efficient algorithm is the one that has capability to embed the data in different types of file format.

LSB EMBEDDING TECHNIQUE
LSB embedding is a simple technique to implement the steganography. Like other techniques, this technique also embeds the data into the cover image so that it cannot be detected by the normal human vision. In LSB technique, the In this technique the last bit of the first pixel, third pixel and fourth pixel is changed in order to make the last bit's value equal to the corresponding bit of the secret data 01100101 to be embedded in the image. By this approach the data is embedded into the image which results in loss of some data but it is indistinguishable to the human vision as its variation in the color is relatively very small.

LITERATURE REVIEW
Several contributions have been made in the field of information security. In recent year both steganography and cryptography achieve a diversified level of security. Different steganography techniques like patchwork, spread spectrum, [1] has been implemented on various image file type like BMP,GIF,JPEG etc formats with different combination of other techniques like LSB with BMP, LSB with GIF,JPEG compression [1]. So many work is done with technique named as least significant bit(LSB) with concern of various issues such as quality, security and data capacity [2]. As defined above, steganography is all about hiding data in an image so the security feature cannot be ignored. The work done named as dual image steganography, in which steganography used within steganography focused on enhancing security and payload capacity. Other technique which enhances the basic LSB named as Smart LSB Pattern Substitution algorithm [10]. The basic concept of cryptography and steganography is explained. It proposes 3 different types of patterns to embed secret data bits into the image bytes. Also, the hiding capacity can be increased by up to 4 times by configuring the hiding capacity level. Based on this work analysis we proposed a new algorithm which covers up the various limitations and give new ways to handle medical scanned images with a hybrid solution using steganography and cryptography.

PROPOSED WORK
A new hybrid algorithm is being proposed which is an enhancement to the medical field. In these both, techniques cryptography and steganography are used to increase the security of the data of the patient which is stored in the digital image of the patient X-ray.

Embedding Algorithm
 Read the text message into the string form.  Encrypt the text message using the AES encryption technique.  Convert the encrypted text into the binary form.  Read the cover image into the 1D array i.e. binary form.  Select the last bit of the image and place the last bits in an array.  Convert 1d array to 2d array in 3*3 forms.  Logical grids of 3*3 are made having the last bit replaced with the MSB of the encrypted text.  Now again from new grid make an array and replace these bits with the image last bits row vice.  Data is embedded resulting into the creation of the stego image.

Extracting Algorithm
 Read the stego image into 1D array form.  Convert the decimal values into binary form.  Select the last bit of the stego image converted decimal and make an array of these bits.  A grid of 3*3 is made and result is stored in 2D array.  Convert this 2D array into 1D array.  Convert these binary values into a string.  Decrypt this string using AES decryption algorithm, which results in the original text.  The cover image and the original text regain.

RESEARCH METHODOLOGY
The approach is divided into two modules: embedding data and extraction of data from the patient scanned x-ray. The first module contains two main techniques: cryptography and steganography. In this the patient instead of any paper report is provided with the x-ray scanned containing the patient history and diagnosis. The second module contains the stego extraction, decryption algorithm and one added technique by which the doctors diagnose and patient history both is stored in the database for future reference. The flow of the research is: . Fig.2. Research flow.

CONCLUSION
The proposed approach is a dedication to the medical field. The research is on making patient information more secure and disease diagnosis more accurate. The research concerns with using the two important security mechanismscryptography and steganography, on single platform. To make the patient's information more secure with the hospital, the approach explained in the research is about making doctors treatment more secure by providing the diagnose of the previous doctors. As the hospitals are getting digitized, all the data of the hospital are stored in the digital images like CT-SCAN and X-rays. This approach can be an asset to the medical field and can increase the security of the patient data.

ACKNOWLEDGMENT
The paper is written under guidance and support of my department who encouraged me in completion of the work. I would like to thank everyone who helped and motivated me by which the work is made possible.