Srihari Sridharan

A Computationally Secure Randomized Method for Cryptography and Spatial-Domain Steganography

Cryptography deals with the design of algorithms for encryption and decryption. In this paper a computationally secure cryptographic algorithm which uses 64-bit keys for encryption and decryption of data is proposed. Steganography is the art of passing information in a manner that the very existence of the message is unknown. The goal of steganography is to avoid drawing suspicion to the transmission of a hidden message. If suspicion is raised, then this goal is defeated. In this paper, the drawbacks in current spatial domain steganography software are listed and rectified. In this paper, a new data hiding method for storing secret data inside images and audio files in spatial domain is proposed. The proposed method stores data inside image and audio files using a pseudorandom generator, which makes detection of hidden information difficult, even if presence of hidden information is known. The proposed method doesn't require the aid of a cryptographic algorithm to make the data secure, although a cryptographic algorithm can be used for additional security. In the proposed method, the data to be embedded may be plain text or cipher text obtained by applying the plain text to a cryptographic algorithm. A password obtained from the user is used to initialize the pseudorandom generator. The location of the bytes where data is embedded is determined by the next value generated by the pseudorandom generator. The data is embedded in the least significant bit. The pseudorandom generator produces the same sequence of values when it is initialized with a particular seed. This fact is used for the decoding process, where the seed is generated from the password. A new procedure has been developed for data encoding without manipulating the cover media, based on its contents. In this method a log file is generated for the files that are to be secretly transmitted through the network. The log file is encrypted and sent along with the cover media to the other end. The cover media can be a file of any format.