CHAPTER 1
What is cryptography?
Cryptography is the process of encoding and decoding information, messages and files using secret code with the purpose of offering privacy and security. This can be accomplished through machines, computer programs, or both.
Cryptography is always used when there is a need to transmit information in a secure way between two parts, ensuring that only the sender and the receiver will be able to decipher its original content. Anyone who tries to intercept it without authorization will only see a bunch of symbols and codes that makes no sense, and will not be able to decipher it.
Cryptography has existed for thousands of years, but for most part of its history it was considered a military tool, being used almost exclusively by governments and armies due to its high cost and complexity.
Things started to change with the emergence of personal computers and the internet. With the advent of those technologies, high level cryptography became affordable to the general public at the same time that the need for more secure systems was increasing.
Today cryptography is essential for many areas in our society and it is employed in a variety of systems including personal computing, mobile phones, banking systems, magnetic cards, ATM machines, electronic commerce, data storage, wireless devices, etc. However few users are aware of cryptography's presence in our life, and even fewer know how to use it or how it works internally.