- DES = Data Encryption System
- 2DES
- 3DES
- AES = Advanced Encryption System
- 2DES = Encrypt twice using 56 bits, same follows for decrypt.
- It compromised due to Meet in the middle attack
- Some plain text and cipher text needs to be known in order to compromise the 2DES
- K1 -> K2 - Encrypt
- K2 -> K1 - Decrypt
- Encrypted and Decrypted - when value matches, the key is cracked.
- Encrypt(k1,p) = Decrypt(k2,c)
- k1=k2
- 3DES = using two keys, but reverses the cipher, it can also use three keys, the only extra action that's performed here is reversing the cipher during the encryption.
- Using 2 keys = 112 bit
- Using 3 keys = 168 bit
- In decryption, the process is just reversed.
- Weakness in DES:
- Weak Keys - 2 power 56 -> Brute Force
- Mid Term
- 20 marks - 1.5 hours
- 5 Questions
- Q1 MCQs (total 10), 5 marks
- Q2 Practical - Packet Tracer - enable, conf t, show running config, 2 marks
- Q3 Theory - VPN related question, 3 marks
- Q4 Cipher - 5 marks
- Q5 Cipher - 5 marks.
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