Implementation of LSB Steganography and its Evaluation for Various File Formats(2010)

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          Steganography is derived from the Greek word steganos which literally means “Covered” and graphy means “Writing”, i.e. covered writing. Steganography refers to the science of “invisible” communication. For hiding secret information in various file formats, there exists a large variety of steganographic techniques some are more complex than others and all of them have respective strong and weak points. The Least Significant Bit (LSB) embedding technique suggests that data can be hidden in the least significant bits of the cover image and the human eye would be unable to notice the hidden image in the cover file. This technique can be used for hiding images in 24-Bit, 8-Bit, Gray scale


Image compression techniques are extensively used in steganography. Among the two types of image compressions, lossy compression and loss less compression; lossless compression formats offer more promises. Lossy compression compression may not maintain the original image’s integrity. Lossless compression maintains the original image data exactly, hence it is prefered. Example of Lossy compression format is JPEG format files. Examples of Lossless compression formats are GIF[3] and BMP formats.


          The “Data Hiding in Audio Files” mainly developed to embed or extract the messages into audio files. This project basically deals with two important network security concepts namely steganography and encryption. For encryption AES algorithm is used. The plaintext is given as input. The plaintext is encrypted using AES algorithm. The ciphertext is given as output. The output ciphertext is hidden into the audio files using Seganography. For steganography LSB algorithm is used. The audio file is in the wave format is the chosen medium to conceal and transmit the secret information. Since the audio file is in ASCII format, the contents of the text file are also converted to the bit stream. The encrypted file is now embedded behind the audio file by mixing the contents together using LSB algorithm. At the other end, the encrypted file is separated from audio file. The encrypted file is then decrypted and the original text file contents are then viewed.


There are two types of Implementation

  • Implementation of a computer system to replace a manual one.
  • Implementation of a new computer system to replace an existing one.



The Advanced Encryption Standard (AES Algorithm) is a computer security standard that became effective on May 26, 2002 by NIST to replace DES. The cryptography scheme is a symmetric block cipher that encrypts and decrypts 128-bit blocks of data. Lengths of 128, 192, and 256 bits are standard key lengths used by AES Algorithm. The algorithm consists of four stages that make up a round which is iterated 10 times for a 128-bit length key, 12 times for a 192-bit key, and 14 times for a 256-bit key. The first stage "SubBytes" transformation is a non-linear byte substitution for each byte of the block. The second stage "Shift Rows" transformation cyclically shifts (permutes) the bytes within the block. The third stage "Mix Columns" transformation groups 4-bytes together forming 4-term polynomials and multiplies the polynomials with a fixed polynomial mod (x^4+1). The fourth stage "AddRoundKey" transformation adds the round key with the block of data. In most ciphers, the iterated transform (or round) usually has a Feistel Structure. Typically in this structure, some of the bits of the intermediate state are transposed unchanged to another position (permutation). AES Algorithm does not have a Feistel structure but is composed of three distinct invertible transforms based on the Wide Trial Strategy design method. The Wide Trial Strategy design method provides resistance against linear and differential cryptanalysis. In the Wide Trail Strategy, every layer has its own function: The linear mixing layer: guarantees high diffusion over multiply rounds.The non-linear layer: parallel application of S-boxes that have the optimum worst-case non-linearity properties.


Data hiding in the least significant bits (LSBs) of audio samples in the time domain is one of the simplest algorithms with very high data rate of  additional information. The LSB watermark encoder usually selects a subset of all available host audio samples chosen by a secret key. The substitution operation on the LSBs is performed on this subset, where the bits to be hidden substitute the original bit values. Extraction process simply retrieves the watermark by reading the value of these bits from the audio stego object. Therefore, the decoder needs all the samples of the stego audio that were used during the embedding process. The random selection of the samples used for embedding introduces low power additive white Gaussian noise (AWGN). It is well known from the psychoacoustics literature [6] that the human auditory system (HAS) is highly sensitive to AWGN. That fact limits the number of LSB that can be imperceptibly modified during watermark embedding. As the number of used LSBs during LSB coding increases or, equivalently, depth of the modified LSB layer becomes larger, perceptual transparency of stego objects is decreased. Therefore, there is a limit for the depth of the used LSB layer in each sample of host audio that can be used for data hiding. Subjective listening test showed that, in average, the maximum LSB depth that can be used for LSB based watermarking without causing noticeable perceptual distortion is the fourth LSB layer when 16 bits per sample audio sequences are used. The tests were performed with a large collection of audio samples and individuals with different background and musical experience. None of the tested audio sequences had perceptual artifacts when the fourth LSB has been used for data hiding, although in certain music styles, the limit is even higher than the fourth LSB layer. Robustness of the watermark, embedded using the LSB coding method, increases with increase of the LSB depth used for data hiding. Therefore, improvement of watermark robustness obtained by increase of depth of the used LSB layer is limited by perceptual transparency bound, which is the fourth LSB layer for the standard LSB coding algorithm. 


Hardware Specification

.   Processor         :           Pentium IV

.   RAM                    :           256 MB

.   CPU Clock         :           1.6 GHz

Software Specification

     .   Front End        :           JAVA

.   Back End        :           MS-Access

.   Platform          :           Windows XP

.   Web Server    :           TOMCAT

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