A basic Encryption Decryption System

Encryption

• Transforming information from readable format to unreadable format.
• Encryption Algorithms can be used to encrypt data.

Decryption

• Transforming from unreadable format to readable format
• Decryption Algorithms can be used to decrypt data.

Key

• A string of bits used by a cryptography algorithm to transform plain text into cipher text or vice versa.
• Key remains private and secures communication.

Plain text 

 The original message (before encrypting) is called as plain text

Cipher text

   The transformed message (after encrypting) is called as Cipher text.

Cryptanalysis

• Techniques used for decrypting a message without any knowledge of the encryption details.
• "Breaking the code"

Brute force attack

• Trying every possible key until an intelligible translation of the ciphertext into plaintext is obtained.

Two Techniques

1. Symmetric Cryptography

• Also called secret key/private key cryptography
• Same key used for Encryption & Decryption.

2. Asymmetric Cryptography.

• Also called public key cryptography
• A pair of keys is used for encryption and decryption.