2•Cryptography is the science of information security.•The word is derived from the Greek kryptos, meaning hidden.•Cryptography includes techniques such as microdots, merging words with images, and other ways to hide information in storage or transit.
3•Confidentiality:- The information cannot be understood by anyone for whom it was unintended.•Integrity :-The information cannot be altered in storage or transit between sender and intended receiver without the alteration being detected.•Authentication :-The sender and receiver can confirm each others identity and the origin/destination of the information.
5•Encryption – It is a process of changing or converting normal text or data information into Cipher text.•Decryption – It is a process of changing or converting Cipher text back to correct message or data by using encryption method.
7•A single common encryption key is used to encode and decode messages.• Both sender and receiver must know the common key.• The common key need to be exchanged before hand by some other secure method.• Symmetric encryption is simple and fast.• But - key management is impractical with large number of senders and receivers. 11
9•Asymmetric system under, which two different keys are used to encrypt and decrypt the message or received data packet.• On public key is used to encrypt the data or message and the private key on receiving end is used to decrypt the message or data packet.• Each user has a Public key and a corresponding Private (secret) key 12