Yang Ren-er, Zheng Zhiwei, Tao Shun, Ding Shilei, Image Steganography ... Van Overtveldt Jeroen Doggen, Maarten Weyn and Jerry Bracke and Suprakash.
Available online at www.sciencedirect.com
ScienceDirect Procedia Computer Science 78 (2016) 610 – 616
International Conference on Information Security & Privacy (ICISP2015), 11-12 December 2015, Nagpur, INDIA
Secure localisation of wireless devices with application to sensor networks using steganography Ankita Tondwalkara* Dr.Preetida Vinayakray-Janib a b
Dept of Electronics and Telecommunication Engineering,SPIT,Mumbai-400034,India. Dept of Electronics and Telecommunication Engineering,SPIT,Mumbai-400034,India.
Abstract The data collected from the sensor network is meaningful to most of the wireless sensor network applications if and only if it is coupled with the exact positioning of the node. Mere localisation solves the problem of locating an unknown node, however applications like battlefield surveillance or enemy tracking, rescue-operations as well as monitoring of military facilities demand security and reliability of the location information. Therefore secure localisation of non-reference nodes facilitates the localisation system to be robust and secure in adversarial circumstances. The work targets secure localisation of the node position using least significant bit (LSB) insertion technique of steganography. In order for a node to be aware of its position, it sends a cover-image along with the node-id to the Cluster head (CH). The CH which already knows the node position performs LSB embedding on the cover image to generate a stego-image. The stego-image and the cover-image are then compared to get secure position information. The comparison will yield accurate position information only if the cover image is the same. For an adversarial circumstance (different cover image), the security mechanism is robust, and the information will be conveyed to the intended recipient only. © byby Elsevier B.V.B.V. This is an open access article under the CC BY-NC-ND license © 2016 2016The TheAuthors. Authors.Published Published Elsevier (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the ICISP2015. Peer-review under responsibility of organizing committee of the ICISP2015
Keywords–Localisation; security; LSB; Cluster-head; node-id; Steganography; stego-image; cover-image. _____________________________________________________________________________________________ 1.
Introduction
Steganography is an art and science of embedding hidden message in a way that is undetectable to anyone else but the recipient who is aware of the existence of the secret message. The word steganography comes etymologically from the Greek words Steganos, meaning secret message and Graphic, meaning writing and is literally hide the written message. The military, rescue and search operations as well as the battle field surveillance and other emergency applications require the accurate position information. Any modified or incorrect data deters the success of these applications. Thus if the localisation is not coupled with a security mechanism the entire purpose of localisation is meaningless. This facilitates the need to collaborate the localisation with a robust mechanism to ensure secure transfer of data. The terrestrial architecture is susceptible to many network attacks along with the possibility of the intruder interfering with the localisation process and thereby replaying the false information. There are numerous ways by which security can be achieved. However this paper targets security via steganography as this steganographic technique is robust, involves less overhead wrt to key management. For the
1877-0509 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of organizing committee of the ICISP2015 doi:10.1016/j.procs.2016.02.107
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LSB approach, pointer always points to the LSB bit, so the steganographic approach becomes relatively simpler to implement. If we use steganography on the higher order bits, the difference between the cover and the stego-image will be too large. This will make the secret message vulnerable to any network attack. Steganography in combination with localisation offers a more reliable and a robust security solution which is of utmost importance in a terrestrial environment. The node position obtained from terrestrial localisation can be securely communicated through Cluster-heads (CHs) via steg-links. The steg-links are established between the communicating entities if and only if both the end points share the same cover image, thus providing for a covert channel. Steganography significantly minimises the problem of unsecured localisation details and provides for authenticate untampered and a secure node position data in a clustered network architecture of Wireless Sensor networks. Text Secret message is hidden in a text file. Most common approach and is rarely used as the text files have a very small amount of redundant data.
Image
Audio/Video
Protocol
Secret message is hidden in an image.
Secret data is hidden in an audio signal.
The TCP/IP protocol (header field) is used to hide the secret message.
The message is embedded using an insertion and extraction algorithm with the same secret key.
Audio embeds Information in an innocuous cover speech in a robust manner and video hides any kind of files in any extension into a video file.
Embeds information within the header field of the network protocols such as TCP/IP.
Concealing data in a message requires the following elements: x Cover- image (Carrier where data is hidden) to embed the secret message. x Secret message of any plain text, digital image, or any other form of data. x Steganographic methods of embedding and extraction of the secret message. x Stego-key which may be used to insert and extract the data. The paper has been organised as follows. Section II provides the detail about background followed by System overview in Section III. The proposed system model considers image based steganography approach to find the position of the localised nodes. Section IV analyses the simulation results finally followed by conclusion in Section V. 1.1. Literature Survey In [3], a new steganographic algorithm is proposed that is use to hide text file inside an image using compression algorithm. This steganographic technique has a maximum compression ratio of 8 bits/ pixel. In the proposed technique an input text file is converted into its binary equivalent and the corresponding number of bits are calculated. A sample cover image for hiding the information is selected and converted to it’s corresponding RGB image, with the total count of pixels that make up the image after which the compression function is employed. If the number of bits match the image resolution, the red component of the first character with the first pixel, green of the second character with the first pixel and blue component of the third character with the first pixel is replaced, until all the pixels are exhausted. For cases in which there is a mismatch between the counted pixels and image
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resolution, the necessary compression ratio is found and the necessary bits as defined by the compression ratio are replaced in immediate component of each pixel. A security key is provided after the completion of the encryption process and another cover image is made use of to hide the distorted image. [4] provides significantly higher embedding capacity with slightly worse image quality in comparison with a method of shifting nonzero coefficients only. In the paper, the concept of image being divided into 8x8 non-overlapping blocks and processed in the frequency domain by using discrete cosine transform (DCT) followed by quantization block by block is exploited. Each block consists of integer values where the leftmost and topmost value is a DC coefficient value, and the remaining 63 coefficients are AC coefficient values. The DC coefficient maintains an average luminance value of the block. As a result of which it is not used for inserting data due to serious possibility of blocking effects among neighbouring blocks. The S and T blocks are found out by the total count of nonzero AC coefficients present. The AC coefficients to the left and the top positions close to the DC coefficient are considered to be more important than the AC coefficients to the right and the bottom positions far from the DC coefficient.The algorithm permits shifting of nonzero AC coefficients to make either even or odd number of zeros in between two nonzero coefficients for the purpose of hiding data. Importance of the coefficients can be measured by the magnitudes of the associated quantization coefficients. It is a known fact that low-frequency components are more important than high-frequency components in data compression. Comparison of the threshold value with the AC coefficients helps to determine S and T JPEG block. Paper [5] proposes a secure communication system that employs cryptographic algorithm together with steganography. A discrete wavelet transforms (DWT) based steganography is employed to hide the encrypted message in the cover image by modifying the wavelet coefficients. The main four stages which the message goes through is the Encryption, Embedding, Extraction and Decryption. In this system, the encryption process is achieved using the filter bank cipher, which presents a high speed and level of security. The insertion process is accomplished using the discrete wavelet transform based steganography. Work in [6] is targeted to maintain the trade-off between the complexity level of algorithm and security level of message considering the time factor. The proposed work has evolved with two algorithms: ASCII Message Encryption and Decryption Technique to protect secret message and ASCII Message Embedment and Extraction Technique to embed encrypted text to digital image. The implementation of these algorithms has resulted in justifying higher level of security with comparatively lower level of complexity of algorithm. This research work has a limitation with regard to the size of message to be communicated has to be less than 255 characters in size. 2. System-Overview The system model comprises of the randomly deployed mobile sensor nodes (location already calculated using localisation method) and the static beacon nodes called Cluster head (known position) indicated by yellow circle and red triangle respectively. The system model is defined in a square area of 100 m * 100 m. The nodes along with the cover-image and node-ids send a request to their within range CHs for obtaining the position information. The corresponding CHs uses LSB insertion mechanism resulting into the transformation of a simple cover-image to a stego-image.The stego-image consists of the original cover-image and the node location data. The stego-image is then sent back to the nodes, which compare the two images and extract the location information of the node.
Fig. 1. (a) System Model
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3.
Steganography
3.1. LSB Steganography There are many versions of spatial steganography, all of which directly change some bits in the image pixel values by the value of the secret message to the intended receiver. Least significant bit (LSB)-based steganography is one of the simplest approach that hides a secret message in the LSBs of pixel values without indistinguishable distortions. To our human eye, changes in the value of the LSB are very insignificant. The LSB of some or all of the bytes inside an image is replaced by the bit of the secret message. The robustness of this method is wrt to the same cover image shared between the unknown node and the Cluster head in the network.
Fig. 2. (a) LSB Insertion
(b) LSB Extraction
Figure above shows the LSB insertion and extraction process. The LSB insertion is carried out at the transmitter where the secret message after being converted to its binary equivalent is passed through the encoder to get a stego image. The stego image is obtained by inserting binary value of the message in each first component of next pixel. This stego image is passed through the decoder to extract the intended secret message. Starting from the first pixel, the stego image values are extracted from first component of the pixels. Methodology Algorithm 1 My algorithm 1: procedure MYPROCEDURE 2. loop 3: CH Node request 4: CH uses LSB insertion 5: CH StegoÅ image 6. loop 7: Stego-image and Cover-image comparison 8: Node positionÅDifference 9. Position known to the node 10: goto loop. 11. close; 12. goto top.
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3.2. Algorithm-Description 3.2.1. Localisation The localisation information is obtained by employing the Angle of arrival (AoA) and the triangulation method of the distance and position estimation techniques respectively. The mobile nodes are randomly deployed in the network, with unknown nodes and few anchor nodes with the latter assisting the localisation process. Initially the CH broadcasts the signal to the entire network at a reference angle, and the AoA of each node is calculated. Further which at least two CH’s are required to determine the position of the node using the already found out angular information. The initial position of all the nodes wrt the assumed reference position assumed is compared with the obtained position and it’s Mean square analysis is carried out to study the location accuracy and the speed of the nodes in the given network density. 3.2.2. Steganographic-Method The unknown node compares the cover-image and the stego-image received and the resultant image difference is actually the desired position information. The node forwards a request to extract its position information to the CH along with its ID and a cover image. The CH using LSB Insertion steganographic technique embeds the binary equivalent of the position into the binary bit stream of the pixel value of the cover image. The node on receiving the stego-image compares it with the original cover image it sent, and finds out its position. The technique is secure in a way that only the node having a cover-image can get to know of the location. Any other node or an attacker impersonating itself as a part of the network cannot interfere with the localisation process using a different cover image. An attacker with a different cover-image cannot gain access to the information hidden in the cover-image and thereby possesses no security threat. The LSB steganographic approach provides for a secure, reliable and attack resistant communication process of the information. The Cluster head communicates the intended data to the corresponding nod via the steg-links in a covert channel. The steg-link establishment happens only after the verification of the fact that the communicating end points have the same cover-image. 4. Simulation and Results Assumptions For the sake of simplicity, the following assumptions were taken into consideration. x Node failure is ignored. x All of the nodes in the network are multimedia nodes. To analyse the security of the localised information using steganography, Network Simulator (NS-2.32) is used. In a square area of area of 100 m *100 m, the nodes are set up. The simulation parameters used for simulation are tabulated as below:
Parameters
Type
Simulation Area
100 *100
Number Of Mobile nodes
50
Channel
Wireless
Radio Propogation Model
Two-ray Ground
Network Interface
Wireless Physical
Antenna
Omnidirectional
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Fig. 3. (a) Cover-image
Fig. 4. (a) Histogram of Cover-image
(b) Stego-image
(b) Histogram of Stego-image
5. Conclusion In the paper, we have analysed the security of the localised information sent by the Cluster-head to the unknown node in the network. The security mechanism is robust enough to sustain an adversarial circumstances of different cover image used by the attacker node. The security is ensured on the basis of the originality of the cover-image. The secure exchange of position information is guaranteed as no other node will be able to decode the hidden information until and unless it has the same cover image as the received modified cover-image. The result analysis shows the cover image and the stego-image to be the same, thus securely communicating the location information without the knowledge of the adversary However if we use steganography on the higher order bits, the difference between the cover and the stego image will be too large. This will make the secret message vulnerable to any network attack. Higher order bits contain large part of the information. Applying steganography over such bits, introduces significant errors.
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