1. S. Muftic Computer Networks Security 1 Lecture 4: Message Confidentiality and Message Integrity Prof. Sead Muftic

2. S. Muftic Computer Networks Security 2 Lecture 4 : Message Confidentiality and Integrity Message Confidentiality and Integrity Subjects / Topics : 1. Basic principles of message protection 2. Message confidentiality 3. Message integrity

3. S. Muftic Computer Networks Security 3 Lecture 4 : Message Confidentiality and Integrity Message Confidentiality and Integrity Subjects / Topics : 1. Basic principles of message protection 2. Message confidentiality 3. Message integrity

4. S. Muftic Computer Networks Security 4 Some confidential text (message) in clear (readable) form Network Aspects : * selection of algorithms * format of messages * message filtering * format of messages * message filtering Message Confidentiality

5. S. Muftic Computer Networks Security 5 Someconfid entialtext essage) inclear Aspects : 1. Algorithms: 3DES, 3DES-CBC, IDEA,... 2. Mode, padding 3. Filtering of cryptograms 4. Integrity of cryptograms 5. Exchange of keys 5. Exchange of keys Significant Aspects

6. S. Muftic Computer Networks Security 6 Solutions (standards) : * algorithm: 3DES, AES * mode: CBC, padding: Fx, …, Fx * filtering of cryptograms: base64 * integrity of cryptograms: MD2 * exchange of keys: KE protocols * exchange of keys: KE protocols Algorithms – Defaults Someconfid entialtext essage) inclear

7. S. Muftic Computer Networks Security 7 A B Alg-2Alg-1 Negotiation protocol Algorithms – Negotiations

8. S. Muftic Computer Networks Security 8 Algorithms – OIDs RC2-CBC OBJECT IDENTIFIER ::= {iso(1) member-body(2) US(840) rsadsi(113549) encryptionAlgorithm(3) 2} 1 2 840 113549 3 2 RC2 – CBC :

9. S. Muftic Computer Networks Security 9 ENCRYPTED {ToBeEnciphered} ::= HASHED {ToBeHashed} ::= BIT STRING (CONSTRAINED BY { OCTET STRING (CONSTRAINED BY { -- must be the result of -- must be the result of -- applying an encipherment -- applying a hashing -- procedure to the BER-encoded -- procedure to the DER-encoded -- octects of the value of -- -- octetcs of the value -- ToBeEnciphered }) ToBeHashed }) SIGNATURE {OfSignature} ::= SEQUENCE { AlgorithmIdentifier, ENCRYPTED { HASHED {OfSignature}}} Algorithms – Coding

10. S. Muftic Computer Networks Security 10 Network Topology

11. S. Muftic Computer Networks Security 11 Lecture 4 : Message Confidentiality and Integrity Message Confidentiality and Integrity Subjects / Topics : 1. Basic principles of message protection 2. Message confidentiality 3. Message integrity

12. S. Muftic Computer Networks Security 12 Message Encrypted message DES 8888 KK KK8888IV Message Confidentiality – Encryption DESDES DES

13. S. Muftic Computer Networks Security 13 Message Confidentiality – Ciphers Symmetric: DES AES 3DES Blowfish / Twofish IDEA RC2 RC4 etc... Asymmetric: RSA Elliptic Curve ElGamal

14. S. Muftic Computer Networks Security 14 Input message Output message 8888KK KK 8885 IV Message Confidentiality – Padding DES DESDES DES

15. S. Muftic Computer Networks Security 15 Block Cipher Modes – Electronic Codebook (ECB) Message Encrypted message 8888 KK KK8888 DES DESDES DES

16. S. Muftic Computer Networks Security 16 Block Cipher Modes – Cipher Block Chaining (CBC) Message Encrypted message 8888 KK KK8888IV DES DES DES DES

17. S. Muftic Computer Networks Security 17 Block Cipher Modes – Cipher Feedback (CFB) Message Encrypted message 88888888IV DES K DES K DES K DES K

18. S. Muftic Computer Networks Security 18 Block Cipher Modes – Counter (CTR) Message Encrypted message 8888 DES K8888 K K K nonce + counter

19. S. Muftic Computer Networks Security 19 Message Confidentiality – Important Parameters Key Algorithm Padding Mode Cipher Mode IV Nonce + Counter Initial Value

20. S. Muftic Computer Networks Security 20 Lecture 4 : Message Confidentiality and Integrity Message Confidentiality and Integrity Subjects / Topics : 1. Basic principles of message protection 2. Message confidentiality 3. Message integrity

21. S. Muftic Computer Networks Security 21 Some confidential text (message) in clear (readable) form E n c r y p t i o n D e c r y p t i o n Destruction of Cryptograms Someconfi entialtex essage) inclear Someconfi entialtex essage) inclear

22. S. Muftic Computer Networks Security 22 Some confidential text (message) in clear (readable) form 1101 0011 1010 1001 1101 0011 1010 1001 MAC General Data Integrity

23. S. Muftic Computer Networks Security 23 1101 0011 1010 1001 1101 0011 1010 1001 MAC sdefghtmm aassddffh  essage)  inclear Integrity of Cryptograms

24. S. Muftic Computer Networks Security 24 Message MAC KK KK 8888 IV 888 8 Hashing Algorithms DES DES DES DES

25. S. Muftic Computer Networks Security 25 AB MAC Verification Procedure Someconfi entialtex essage) inclear Someconfi entialtex essage) inclear

26. S. Muftic Computer Networks Security 26 Message Authentication based on MAC

27. S. Muftic Computer Networks Security 27 Some confidential text(message) in clear (readable) form 1101 0011 1010 1001 1101 0011 1010 1001 MAC Modification of Message + Hash

28. S. Muftic Computer Networks Security 28 Some confidential text(message) in clear (readable) form 1101 0011 1010 1001 1101 0011 1010 1001 MAC Prevention

29. S. Muftic Computer Networks Security 29 AB Some confidential text (message) in clear (readable) form MAC Some confidential text (message) in clear (readable) form MAC Encryption of MAC

30. S. Muftic Computer Networks Security 30 Encryption of MAC – using Shared Secret

31. S. Muftic Computer Networks Security 31 Encryption of MAC – using Secret Key

32. S. Muftic Computer Networks Security 32 Encryption of MAC – using Private Key

33. S. Muftic Computer Networks Security 33 Lecture 4 : Message Confidentiality and Integrity Message Confidentiality and Integrity Subjects / Topics : 1. Basic principles of message protection 2. Message confidentiality 3. Message integrity

34. S. Muftic Computer Networks Security 34 ? Questions