(IJACSA) International Journal of Advanced Computer Science and Applications, Vol. 7, No. 6, 2016 45 | Page www.ijacsa.thesai.org Secure Steganography for Digital Images Meandering in the Dark Khan Farhan Rafat NUST, Rawalpindi/Islamabad Pakistan Muhammad Junaid Hussain NUST, Rawalpindi/Islamabad Pakistan Abstract—The degree of imperceptibility of hidden image in the ‘Digital Image Steganography’ is mostly defined in relation to the limitation of Human Visual System (HVS), its chances of detection using statistical methods and its capacity to hide maximum information inside its body. Whereas, a tradeoff does exist between data hiding capacity of the cover image and robustness of underlying information hiding scheme. This paper is an exertion to underline the technique to embed information inside the cover at Stego key dependent locations, which are hard to detect, to achieve optimal security. Hence, it is secure under worst case scenario where Wendy is in possession of the original image (cover) agreed upon by Alice and Bob for their secret communication. Reliability of our proposed solution can be appreciated by observing the differences between cover, preprocessed cover and Stego object. Proposed scheme is equally good for color as well as gray scaled images. Another interesting aspect of this research is that it implicitly presents fusion of cover and information to be hidden in it while taking care of passive attacks on it. Keywords—Steganography; Imperceptibility; Information Hiding; LSB Technique; Secure Communication; Information Security I. INTRODUCTION The word Steganography is derived from Greek means “Hidden Writing” [1] and dates back to 440 B.C. [2]. Some earlier examples as reported in [3] include: shaving scalp of a most trusted slave to etch a secret message and waiting for the hair to grow after which he was sent to allies who retrieves it by reshaving his head; engraving messages on wooden Tablet and then covering it wax. The receiver retrieves it by melting the coated wax. A comprehensive insight on unconventional steganographic schemes has well been elucidated in [4]. Steganography is an ancient art [5] that with technological revolution has now been evolved into a science [6] to avert detection of hidden data. [7] delivered terminology for steganography while Simmon [8] gave the first model for steganography by discussing the scenario of Alice and Bob held in separate prison cells had to communicate through Warden Wendy. Types of steganographic system are discussed in [9] as pure (with no Stego key), private key and public key respectively whereas three techniques for steganography including insertion, substitution and cover generation have been discussed in [10]. Cryptography, having Greek origin and with same inception period as that of steganography, means “Secret Writing” [11] the essence of which is to inarticulate secret information in contrast to steganography whose sole perseverance is to conceal the fact that such information does really exist. Though opposite to each other in their approach, these two serves well as a double edged weapon to safeguard information security frontiers [12-14]. The mammoth growth of internet as communication medium has insentiently provided an opening for surreptitious communication that has been exploited in full by academics and mavens through variety of file formats (as hidden information carrier) that exist for text, image, audio and video etc. storage and representation. This paper besides presenting an innovative secure scheme for LSB based image steganography, also expounds on predominant misconception regarding detection and that for favoring bulk of online data exchange. The paper is planned as follows: Section II introduces reader with basics of image steganography. Following this, in Section III, is the literature review of some the most recently published research articles on LSB based steganographic schemes. Theoretical foundation to disregard misapprehension of detection of steganography is the prima facie of Section IV. Section V elaborates on the proposed secure data hiding scheme while Section VI presents test results. Misapprehension about cover’s capacity is discussed in Section VII. Technical analysis of the proposed logic is given in Section VIII. Advantages of the proposed scheme are highlighted in Section IX. Future work comes in Section X and Section XI concludes the discussion. II. BRASS TACKS An image can be thought as a logical arrangement of color(s) perceived by human as an object. A digital image on the other hand is viewed as a two dimensional function i(x, y), where x and y are plane coordinators pointing to a unique value, corresponding to light’s intensity [15] at that point, and stored as raw data inside persistent storage which gets its meaning from the header that precede and relates it to a specific file format e.g., BMP, JPEG, TIF etc. Image can be stored as black and white, 8-bit (mishmash of black and white colors) as shown in Fig. 1 in the form of 8 x 32 matrix, 16-bit or 24-bit files. A 24-bit color image is expressed in terms of multiple groups of 3-bytes each analogous to red, green and blue colors called RGB colors that tally to 2 ^ 24 – 1 colors in total, but 8-bit images for steganographic purposes are more suitable because it offers steady transformation of shades (from 0 ~ 255). 16-bit images have varied RGB representations such as 5 (R), 6 (G), 5 (B) / 5, 5, 5 (excluding LSB) bits etc. [16-17].