1. WTLS (Wireless Transport Layer Security) Youngho Choung Yhchoung@cs.uh.edu

2. Youngho Choung Contents Why we need WTLS? What is WTLS? What is TLS (SSL3.0) ? WTLS Functions Security Algorithm WTLS specifications Other Technologies

3. Youngho Choung Why we need WTLS ? (1/2) What can we do through the Cell Phone?  Communication  Using Internet  E-commerce  On-line banking  Trading Stock  Electric Cash  Electric ID  Watching movie, take a picture … etc …

4. Youngho Choung Why we need WTLS ? (2/2) Environment problems We need Security Solutions

5. Youngho Choung What is WTLS ? (1/2)

6. Youngho Choung What is WTLS ? (1/2)

7. Youngho Choung What is TLS (SSL3.0) ? (1/3) TLS stand for Transaction Layer Security SSL stand for Secure Socket Layer Customer 웹 브 라 우 저 인터넷 Internet Shopping Mall 불안전한 Unreliable Channel 암호화구간

8. Youngho Choung What is TLS (SSL3.0) ? (2/3) Application data Fragment Compress Add MAC Encrypt Append SSL record header SSL Handshake Protocol SSL Change Cipher Spec Protocol SSL Alert Protocol HTTP SSL Record Protocol TCP IP

9. Youngho Choung What is TLS (SSL3.0) ? (3/3) Handshake protocol  K ey establishment algorithm Diffie-Hellman, RSA, Fortezza  Certificate RSA, DSS,Fortezza Record protocol  MAC algorithm MD5, SHA-1  Encryption algorithm RC2, RC4, DES, Triple DES, IDEA,Fortezza

10. Youngho Choung WTLS Functions Data Integrity Privacy Authentication DoS (Denial of Service) protection Optional

11. Youngho Choung Security Algorithm Hash Function Dyejsmldmnf mdfnmd,sdd fnfnfnlkfekkfe ekfkjefjefelfee ---------------- Any Length Plain Text Hash Function Fix length Encrypted Text MD5, MD4, Hash, SHA-1, etc

12. Youngho Choung Security Algorithm Block Cipher (1)Diagram M E C (Message) (Ciphertext) K (Key) M, C, K : nbit blocks Examples ( in bits) {128,192,256} AES 64 DES KCM

13. Youngho Choung Security Algorithm Block Cipher (2)Encryption : Combination ofSubstitution& Permutation Decryption : Inverse of Encryption (3) Classical ciphers a.Permutation Ciphers b.Substitution Cipher : Caesar Cipher

14. Youngho Choung Security Algorithm Public Key Key distribution is difficult  Tow Communicants already share a key or have the use of a key distribution center Characteristic  (public) encryption key ≠ (private) decryption key

15. Youngho Choung Security Algorithm Public Key

16. Youngho Choung WTLS Specifications (1/5) Handshaking protocol  Full handshaking protocol  Abbreviated handshaking protocol  Optimized handshaking protocol Alert protocol Change Cipher spec protocol Record protocol

17. Youngho Choung WTLS Specifications Full handshaking

18. Youngho Choung WTLS Specifications Abbreviated handshaking

19. Youngho Choung WTLS Specifications Optimized full handshaking [ChangCipherSpec] Finished Application Data ServerHello Certificate [ChangeCipherSpec] Finished

20. Youngho Choung WTLS Specifications (4/5) Alert protocol Change Cipher spec protocol

21. Youngho Choung WTLS Specifications (5/5) Record Protocol

22. Youngho Choung Let ’ s talk about …… later.. Let ’ s talk about …… later.. WALS(Wireless Application Layer Security) WPKI(Wireless Public-Key Infrastructure) WIM(WAP Identity Module References