Cryptography: Secret Key

This lecture covers the concept of secret key cryptography, where a shared secret key is used to encrypt and decrypt messages. It starts with the 'one-time pad' encryption method, which guarantees 100% security when a key is randomly generated. The lecture then explores the flaws of this system, such as the need to securely share keys and the risks of key reuse. It delves into the Data Encryption Standard (DES) introduced in 1976, explaining its principles and operation. The DES system iterates the encryption process 8 times with an extended key length, enhancing message security. Practical aspects of DES implementation and the complete DES system are also discussed.