12. DES was a great block cipher when it was created. Briefly explain the two reasons why it is no longer great today 13. Describe double-DES (2DES) (not the DES2 from the assignment). Why is 2DES essentially no more secure than DES even though the number of key bits has doubled? Explain the attack involved 14. Triple-DES is a more secure replacement for DES than double-DES. It encrypts, decrypts then encrypts using DES with 3 different keys K1, K2, K3. Explain why anyone might want to use K1-K2-K3