1. System Security: Cryptography Technologies CPE 261403 - Operating Systems http://www.e-cpe.org/moodle

2. What does the fish mean?

3. Ichthys

5. User name / Password

6. Threat Ex: Wifi Packet Sniffers

7. Protection with Cryptography

8. Encryption and Decryption Symmetric – Uses a shared key Asymmetric – Added security with Public and Private keys

9. Symmetric Encryption I LOVE YOU Simple example: Add a constant to the ASCII value J MPWF ZPV Key = 1

10. Some Examples Data Encryption Standard (DES)  56 bit key for every 64 bit value Advanced Encryption Standard (AES)  256 bit key for every 128 bit value RC4  As used in WEP (Wired Equivalent Privacy) WPA, WPA2 (Wi-Fi Protected Access)  256 bit key

11. Asymmetric Encryption

12. Algorithm Example Public Key = (kd, N) Private Key = (ke, N) N = p.q (where p, q are prime numbers) Pick kd that is < N Calculate ke where  ke.kd mod (p-1)(q-1) = 1

13. Example If p = 7 and q = 13 N = 7.13 = 91 Pick Kd = 5 Find Ke  Ke.5 mod (7-1)(13-1) = 1  Ke = 29 Public Key = (5, 91) Private Key = (29, 91)

14. Encrypting and Decrypting Encrypt message = (input ^ ke ) mod N Decrypt message = (input ^ kd) mod N If we want to send the number 69 Encrypted message = 69 ^ 5 mod 91 = 62 Decrypted message = 62 ^ 29 mod 91 = 69 *Note: number must < N

15. Notes In reality p and q can be 512 bits each