what is Cryptography

*  the art of writing or solving codes.

1. *The art of protecting information by transforming it (encrypting it) into an unreadable format, called cipher text. Only those who possess a secret key can decipher (or decrypt) the message intoplain text. Encrypted messages can sometimes be broken by cryptanalysis, also called codebreaking, although modern cryptography techniques are virtually unbreakable.
2.  More generally, it is about constructing and analyzingprotocols that overcome the influence of adversaries^[3]and which are related to various aspects in information security such as data confidentiality, data integrity,authentication, and non-repudiation.^[4] Modern cryptography intersects the disciplines of mathematics,computer science, and electrical engineering. Applications of cryptography include ATM cards,computer passwords, and electronic commerce.