The aim of this book is to provide a comprehensive introduction to cryptography without using complex mathematical constructions. The themes are conveyed in a form that only requires a basic knowledge of mathematics, but the methods are described in sufficient detail to enable their computer implementation. The book describes the main techniques and facilities of contemporary cryptography, proving key results along the way. The contents of the first five chapters can be used for one-semester course.
For centuries, cryptography, as the science of ciphering or covering information from unauthorised use, had been employed mainly for protecting messages communicated between the military or governmental officials. Therefore, the circle of people employing cryptography was quite restricted and the very methods of this science secret. However, in the last decades, when the mankind has entered the information society stage, cryptographic methods of information protection become widely used, serving, in the first place, business needs. At that, not only inter-bank payments carried out over computer networks are meant or, say, electronic exchanges operating via the Internet, but also numerous transactions in which millions of dinary” people are involved every day, such as payments by credit cards, transferring wages onto bank accounts, ordering tickets and buying goods over the Internet, etc. It is a natural demand that all these transactions, as well as mobile phone conversations and electronic mail, be secured against dishonest or just overly inquisitive persons and organisations. Therefore nowadays many specialists working in the field of information technologies (IT) are engaged in designing and- exploiting the systems of information protection. Since many of the methods used thereon are based on the results of contemporary cryptography, this subject is now studied in the universities preparing IT specialists.