WAVELET TRANSFORMS:ONE OF THE IMPORTANT SIGNAL PROCESSING DEVELOPMENTS IN THE LAST DECADE

Wavelet transforms have been one of the important signal processing developments in the last decade, especially for the applications such as time-frequency analysis, data compression, segmentation and vision. During the past decade, several efficient implementations of wavelet transforms have been derived. The theory of wavelets has roots in quantum mechanics and the theory of functions though a unifying framework is a recent occurrence. Wavelet analysis is performed using a prototype function called a wavelet. Wavelets are functions defined over a finite interval and having an average value of zero. The basic idea of the wavelet transform is to represent any arbitrary function f (t) as a superposition of a set of such wavelets or basis functions. These basis functions or baby wavelets are obtained from a single prototype wavelet called the mother wavelet, by dilations or contractions (scaling) and translations (shifts). Efficient implementation of the wavelet transforms has been derived based on the Fast Fourier transform and short-length ‘fast-running FIR algorithms’ in order to reduce the computational complexity per computed coefficient.

CRYPTOGRAPHY

Security of information results from the need for Private transmission of messages. It is very essential that Security coverage should be provided to the computer systems, including to security  to communication channels

Cryptography means hidden writing. Cryptography is used to protect information to which illegal access is possible and where other protective measures are inefficient

The basic idea in cryptography is to take a message in ordinary language, called plain text. This is transformed in some way to produce cipher text. The cipher text can now be sent to the correspondent. He uses another transformation to recover the plain text from the cipher text. The plain text is encrypted or hidden by the first transformation to obtain the cipher text. The cipher text is decrypted by another transformation to obtain the plain text once again. After encryption, cipher text can be transmitted over a data link or stored in a file