Introduction to cryptography

Cryptography is the science and art of hiding the meaning of a communication from unintended recipients. It encrypt the data in such a way that only intended receiver can read the message.

There are two firms of cryptography symmetric key and public key cryptography. In symmetric key cryptography both sender and receiver has common key or secret. This key is called cryptovariable the sender encrypts the message using cryptovariable to produce ciphertext,then the same cryptovariable is used by the receiver to decrypt the message. The main issue with symmetric key cryptography is that if the key is compromised or attacker somehow know the cryptovariable then he can easily decrypt the message.

Another form is public key cryptography,in it all participants have a private key and a public key. The public key is available publicly to anyone but private key is kept secret from all. The main concept behind this is public key is used for encrypting the message and to verify the digital signature whereas private key is used to decrypt ciphertext.