Symmetric Cryptography
    This is the simplest kind of Cryptography that involves only one secret key to encrypt and decrypt information . It is also known as “Secret Key Cryptography”.     Both Sender and receiver should know the key to be able to communicate securely.     For Example: if Mahesh & Shalini wants to communicate using symmetric-key cryptography  then both would have to devise key and use it for every communication.     So Now, Mahesh encrypts his message using shared key, sends encrypted message  to Shalini , then Shalini uses the same key again decrypt message to read.     To demonstration symmetric-key cryptography , I will use AES ( Advanced Encryption Standard ) & .Net Framework in-build library “ System.Security.Cryptograph ”      Output: