18-05-2013, 11:34 AM
Secured Data Transmission using Cryptographic and Steganographic Techniques
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INTRODUCTION
As we enter the age of universal electronic connectivity, electronic eavesdropping and electronic fraud threaten the prosperity of corporations and individuals. Thus, the role of digital security has become increasingly important. The security requirements within an organization have undergone major changes in the last few decades. Before the widespread use of data processing equipment, data and information valuable to an organization were made invulnerable primarily by physical and administrative means. With the advent of computer networks and the internet however, the design of automated tools which ensure security and privacy of information transferred across networks was inevitable. Though there are several security techniques in use, two of the most prominent ones are steganography and cryptography. In this paper , we discuss these two techniques and how their combination can result in an efficient and secure data transfer software.
Steganography
The word steganography comes from the Greek steganos (covered or secret) and -graphy (writing or drawing) and thus means, literally, covered writing. Steganography is usually given as a synonym for cryptography but it is not normally used in that way. Recent advances in computing power and recent interest in privacy has led to the development of techniques to hide messages in otherwise innocuous computer files such as digital pictures and digitized audio. These techniques are now referred to in the aggregate as steganography
Cryptography
Cryptography is the art or science of secret writing, or more exactly, of storing information in a form, which allows it to be revealed to those, you wish to see it yet hides it from all others. A cryptosystem is a method to accomplish this. Cryptanalysis is the practice of defeating such attempts to hide information. The original information to be hidden is called "plaintext". The hidden information is called "ciphertext". Encryption is any procedure to convert plaintext into ciphertext. Decryption is any procedure to convert ciphertext into plaintext. A cryptosystem is designed so that decryption can be accomplished only under certain conditions,
Encryption using Simplified Data Encryption Standard
It was developed by Professor Edward Schaefer of Santa Clara University [SCHA 96]. It has similar properties and structure to DES (Data Encryption Standard) but with smaller parameters. The S-DES encryption algorithm takes an 8-bit block of plaintext and a 10-bit key as input and produces an 8-bit block of ciphertext as output. The S-DES decryption algorithm takes an 8-bit block of ciphertext and the same 10-bit key used to produce that ciphertext as input and produces the original 8-bit block of plaintext. The encryption algorithm involves five functions: an initial permutation; a complex main function which involves both permutation and substitution operations and depends on a key input; a simple permutation function that switches the two halves of the data; the main function again, and finally a permutation function that is the inverse of the initial permutation.
A Detailed Study of S-DES: Algorithm
The S-DES encryption algorithm takes 8-bit block of plaintext and a 10-bit key as input and produces 8-bit block of cipher text as output. The S-DES decryption algorithm takes 8-bit block of cipher text and same 10-bit key used to produce that cipher text as input and produces the original 8-bit block of plaintext.
The encryption algorithm involves five functions: An initial permutation (IP); a complex function labeled fk, which involves both permutation and substitution operations and depends on a key as input; a simple permutation function that switches (SW) the two halves of the data; the function fk again, and finally permutation function that is the inverse of the initial permutation (IP-1). The use of multiple stages of permutation and substitution results in a complex algorithm, which increases the difficulty of cryptanalysis.
Benefits
1. The transmission system implemented provides a higher degree of security. A primary level of security is provided by the S-DES encryption algorithm discussed above. This algorithm is based on DES (Data Encryption Standard) and hence is quite secure.
2. The security of the algorithm is further enhanced by the large value of key space provided to the user. The user is given an option of choosing a key value from 1024 alternatives.
3. Further, another level of security is provided by the steganographic algorithm which hides the cipher text within a carrier file, such as a bitmap image. Thus, the transmission becomes highly secure against electronic eavesdropping.