PowerPoint PresentationChapter 8 roadmapSecure e-mailSlide 4Secure e-mail (continued)Slide 6Slide 7SSL: Secure Sockets LayerSSL and TCP/IPCould do something like PGP:Toy SSL: a simple secure channelToy: a simple handshakeToy: key derivationToy: data recordsToy: sequence numbersToy: control informationToy SSL: summaryToy SSL isn’t completeSSL cipher suiteReal SSL: handshake (1)Real SSL: handshake (2)Real SSL: handshaking (3)Real SSL: handshaking (4)SSL record protocolSSL record formatReal SSL connectionKey derivationSlide 28What is network-layer confidentiality ?Virtual Private Networks (VPNs)Slide 31IPsec servicesIPsec transport modeIPsec – tunneling modeTwo IPsec protocolsFour combinations are possible!Security associations (SAs)Example SA from R1 to R2Slide 39IPsec datagramWhat happens?R1: convert original datagram to IPsec datagramInside the enchilada:IPsec sequence numbersSecurity Policy Database (SPD)Summary: IPsec servicesIKE: Internet Key ExchangeIKE: PSK and PKIIKE phasesIPsec summarySlide 51WEP design goalsReview: symmetric stream ciphersStream cipher and packet independenceWEP encryption (1)WEP encryption (2)WEP decryption overviewEnd-point authentication w/ nonceWEP authenticationBreaking 802.11 WEP encryption802.11i: improved security802.11i: four phases of operationEAP: extensible authentication protocolSlide 64FirewallsFirewalls: whyStateless packet filteringStateless packet filtering: exampleStateless packet filtering: more examplesAccess Control ListsStateful packet filteringSlide 72Application gatewaysSlide 74Limitations of firewalls, gatewaysIntrusion detection systemsSlide 77Network Security (summary)8-1Chapter 8SecurityComputer Networking: A Top Down Approach 6th edition Jim Kurose, Keith RossAddison-WesleyMarch 2012A note on the use of these ppt slides:We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following:If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!)If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material.Thanks and enjoy! JFK/KWR All material copyright 1996-2012 J.F Kurose and K.W. Ross, All Rights Reserved8-2Network SecurityChapter 8 roadmap8.1 What is network security?8.2 Principles of cryptography8.3 Message integrity, authentication8.4 Securing e-mail8.5 Securing TCP connections: SSL8.6 Network layer security: IPsec8.7 Securing wireless LANs8.8 Operational security: firewalls and IDS8-3Network SecuritySecure e-mail Alice: generates random symmetric private key, KS encrypts message with KS (for efficiency) also encrypts KS with Bob’s public key sends both KS(m) and KB(KS) to Bob Alice wants to send confidential e-mail, m, to Bob.KS( ).KB( ).++-KS(m )KB(KS )+mKSKSKB+InternetKS( ).KB( ).-KB-KSmKS(m )KB(KS )+8-4Network SecuritySecure e-mail Bob: uses his private key to decrypt and recover KS uses KS to decrypt KS(m) to recover m Alice wants to send confidential e-mail, m, to Bob.KS( ).KB( ).++-KS(m )KB(KS )+mKSKSKB+InternetKS( ).KB( ).-KB-KSmKS(m )KB(KS )+8-5Network SecuritySecure e-mail (continued) Alice wants to provide sender authentication message integrity Alice digitally signs message sends both message (in the clear) and digital signatureH( ).KA( ).-+-H(m )KA(H(m))-mKA-InternetmKA( ).+KA+KA(H(m))-mH( ).H(m )compare8-6Network SecuritySecure e-mail (continued) Alice wants to provide secrecy, sender authentication, message integrity.Alice uses three keys: her private key, Bob’s public key, newly created symmetric keyH( ).KA( ).-+KA(H(m))-mKA-mKS( ).KB( ).++KB(KS )+KSKB+InternetKS8-7Network SecurityChapter 8 roadmap8.1 What is network security?8.2 Principles of cryptography8.3 Message integrity8.4 Securing e-mail8.5 Securing TCP connections: SSL8.6 Network layer security: IPsec8.7 Securing wireless LANs8.8 Operational security: firewalls and IDS8-8Network SecuritySSL: Secure Sockets Layerwidely deployed security protocolsupported by almost all browsers, web servershttpsbillions $/year over SSLmechanisms: [Woo 1994], implementation: Netscapevariation -TLS: transport layer security, RFC 2246providesconfidentialityintegrityauthenticationoriginal goals:Web e-commerce transactions encryption (especially credit-card numbers)Web-server authenticationoptional client authenticationminimum hassle in doing business with new merchantavailable to all TCP applicationssecure socket interface8-9Network SecuritySSL and TCP/IPApplicationTCPIPnormal applicationApplicationSSLTCPIPapplication with SSL SSL provides application programming interface (API) to applications C and Java SSL libraries/classes readily available8-10Network SecurityCould do something like PGP: but want to send byte streams & interactive data want set of secret keys for entire connection want certificate exchange as part of protocol: handshake phaseH( ).KA( ).-+KA(H(m))-mKA-mKS( ).KB( ).++KB(KS )+KSKB+InternetKS8-11Network SecurityToy SSL: a simple secure channelhandshake: Alice and Bob use their certificates, private keys to authenticate each other and exchange shared secretkey derivation: Alice and Bob use shared secret to derive set of keysdata transfer: data to be transferred is broken up into series of recordsconnection closure: special messages to securely close connection8-12Network SecurityToy: a simple handshakeMS: master secretEMS: encrypted master secrethellopublic key certificateKB+(MS) = EMS8-13Network SecurityToy: key derivationconsidered bad to use same key for more than one cryptographic operationuse different keys for message authentication code (MAC) and encryptionfour keys:Kc = encryption key for data sent from client to serverMc = MAC key for data sent from client to serverKs = encryption key for data sent from server to clientMs = MAC key for data sent from server to clientkeys derived from key derivation function (KDF)takes master secret and (possibly) some additional random data and creates the keys8-14Network SecurityToy: data recordswhy not encrypt data
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