Source: https://www.slideshare.net/kinleay/cryptography-its-history-application-and-beyond Cryptography involves itself with encryption/decryption or hashing of the messages. It’s almost a mathematical field which has a profound practical impact on our lives. Generally, other guys must not be able to read your data, even if they get hold of it and know how it was encrypted.1 Some of the most noticeable everyday life examples: Most n00b example everyone comes across: Fb lbh svanyyl qrpelcgrq guvf! :-C If you didn’t know words are shifted by 13, this would be garbage for you.

Warning! Not your average bitching answer. Well, let’s do a quick recap of what Aadhaar, an authentication system, does. The end-user/application supplies some data to the system, like Aadhaar number, name, age, DOB, etc. which is to be authenticated. The Aadhaar system compares this with its own record, and would like to verify with OTP and biometrics that the authentication request is indeed by the guy whose data is being processed.

Let’s make it interesting. Okay so for a minute think you’re an agent for intelligence agencies like IB/RAW. You have some top secret information about a new weapon system of another country which would wreck havoc in the world. You have to transfer the information obtained by espionage back to Delhi without getting caught, but the bummer is that you know someone named Eve is spying on you and would intercept any message you send.

Almost on every reputed website password isn’t stored in plain-text. It is hashed ( Cryptographic hash function - Wikipedia) and salted. If you store passwords in plain-text then any intruder can just get hold of ’em. A cryptographic hash function is, you can say, a mathematical algorithm (hence a function) to convert an arbitrary input (aka message) to a string (bit array, to be precise) of a fixed size, which is called a hash/digest.