What is cryptograpy????

Cryptography or cryptology (from Greekκρυπτός kryptós, "hidden, secret"; andγράφειν graphein, "writing", or -λογία -logia, "study", respectively^[1]) is the practice and study of techniques for secure communication in the presence of third parties called adversaries.^[2] More generally, cryptography is about constructing and analyzing protocols that prevent third parties or the public from reading private messages;^[3] various aspects in information security such as data confidentiality, data integrity, authentication, and non-repudiation^[4] are central to modern cryptography. Modern cryptography exists at the intersection of the disciplines ofmathematics, computer science, andelectrical engineering. Applications of cryptography include ATM cards, computer passwords, and electronic commerce.

        Modern cryptography concerns itself with the following four objectives:

1) Confidentiality (the information cannot be understood by anyone for whom it was unintended)

2) Integrity (the information cannot be altered in storage or transit between sender and intended receiver without the alteration being detected)

3) Non-repudiation (the creator/sender of the information cannot deny at a later stage his or her intentions in the creation or transmission of the information)

4) Authentication (the sender and receiver can confirm each other?s identity and the origin/destination of the information)

     

        Procedures and protocols that meet some or all of the above criteria are known as cryptosystems. Cryptosystems are often thought to refer only to mathematical procedures and computer programs; however, they also include the regulation of human behavior, such as choosing hard-to-guess passwords, logging off unused systems, and not discussing sensitive procedures with outsiders.