ECE Prof. John A. Copeland fax

Transcription

1 ECE Prof. John A. Copeland fax Office: GCATT Bldg 579 or call for office visit, or call Kathy Cheek, Chapter 7: 07-WebSec.pdf has PDF copies of slides from Chap. 7 of the text, Network Security Essentials, Applications and Standards by William Stallings)

2 Threats Consequences Countermeasures Integrity Modification of data Loss of information Cryptographic checksums Trojan horse browser Modification of memory Compromise of machine Vulnerability to all threats Modification of messages in transit Confidentiality Eavesdropping on the net Loss of information Encryption Theft of info from server Loss of privacy Web Proxies Theft of data from client Info about network configuration Information about which clients talk to server Denial of Service Killing of user threads Disruptive Difficult to prevent Flooding machine with bogus requests Filling disk or memory Annoying Prevent users from getting work done Isolating machines by DNS attacks Authentication Impersonate users Misrepresentation of user Cryptographic techniques Data forgery Belief that false data is valid

3 HTTP FTP SMTP S/MIME PGP SET HTTP FTP SMTP SSL or TLS Kerberos SMTP HTTP TCP TCP UDP TCP IP/IPSec IP IP (a) Network Level (b) Transport Level (c) Application Level Figure 7.1 Relative Location of Security Facilities in the TCP/IP Protocol Stack

4 SSL Handshake Protocol SSL Change Cipher Spec Protocol SSL Alert Protocol HTTP SSL Record Protocol TCP IP Figure 7.2 SSL Protocol Stack

5 Application Data Fragment Compress Add MAC Encrypt Append SSL Record Header Figure 7.3 SSL Record Protocol Operation

6 Content Type Major Version Minor Version Compressed Length encrypted Plaintext (optionally compressed) MAC (0, 16, or 20 bytes) Figure 7.4 SSL Record Format

7 1 byte 1 byte 3 bytes 0 bytes 1 Type Length Content (a) Change Cipher Spec Protocol (c) Handshake Protocol 1 byte 1 byte 1 byte Level Alert OpaqueContent (b) Alert Protocol (d) Other Upper-Layer Protocol (e.g., HTTP) Figure 7.5 SSL Record Protocol Payload

8 Client Server client_hello server_hello Establish security capabilities, including protocol version, session ID, cipher suite, compression method, and initial random numbers. certificate server_key_exchange certificate_request server_hello_done Server may send certificate, key exchange, and request certificate. Server signals end of hello message phase. Time certificate client_key_exchange certificate_verify Client sends certificate if requested. Client sends key exchange. Client may send certificate verification. change_cipher_spec finished change_cipher_spec finished Change cipher suite and finish handshake protocol. Note: Shaded transfers are optional or situation-dependent messages that are not always sent. Figure 7.6 Handshake Protocol Action

9 seed secret HMAC A(1) seed secret HMAC secret HMAC A(2) seed secret HMAC secret HMAC A(3 ) seed secret HMAC length= hash size Figure 7.7 TLS Function P_hash (secret, seed)

10 Merchant Internet Cardholder Certificate Authority Internet Issuer Payment Network Acquirer Payment Gateway Figure 7.8 Secure Electronic Commerce Components

11 PI H PIMD KR c OI H OIMD H POMD E Dual Signature PI = Payment Information OI = Order Information H = Hash function (SHA-1) = Concatenation PIMD = PI message digest OIMD = OI message digest POMD = Payment Order message digest E = Encryption (RSA) KR c = Customer's private signature key Figure 7.9 Construction of Dual Signature

12 PI Request Message Dual Signature OIMD E E K s Digital Envelope PIMD OI Received by merchant Passed on by merchant to payment gateway KU b Dual Signature Cardholder Certificate PI = Payment Information OI = Order Information PIMD = PI message digest OIMD = OI message digest E = Encryption (RSA for asymmetric; DES for symmetric) K s = Temporary symmetric key KU b = Bank's public key-exchange key Figure 7.10 Cardholder Sends Purchase Request

13 Request Message Digital Envelope Passed on by merchant to payment gateway OI = Order Information OIMD = OI message digest POMD = Payment Order message digest D = Decryption (RSA) H = Hash function (SHA-1) KU c = Customer's public signature key PIMD OI H POMD H OIMD Compare Dual Signature Cardholder Certificate D POMD KU c Figure 7.11 Merchant Verifies Customer Purchase Request