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

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

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

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

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

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

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

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

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

S. Muftic Computer Networks Security 10 Network Topology

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

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

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

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

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

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

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

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

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

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

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

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

S. Muftic Computer Networks Security MAC sdefghtmm aassddffh  essage)  inclear Integrity of Cryptograms

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

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

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

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

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

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

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

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

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

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

S. Muftic Computer Networks Security 34 ? Questions