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509 signed by ca computer networks 48 24 12313 pki

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Unformatted text preview: rity is part of 802.11 protocol –  Encrypted message between client and AP; removed aCer AP WPA2 HTTP TCP IP 802.11 Client Computer Networks Contents of 802.11 frame are encrypted 802.11 IP TCP HTTP HTTP TCP IP 802.11 AP 36 18 12/3/13 Home Network •  AP is set up with network password •  Each client also knows password •  Client proves it knows password » –  AP grants network access if successful Internet Client AP Computer Networks 37 Home Network (2) •  For access, client authen7cates to AP » –  Both compute a shared session key based on the password –  If client knows the session key it has proved that is has the password •  For usage, client/AP encrypt messages –  For confiden7ality, integrity/authen7city –  No access without the session key –  Also group key for AP to reach all clients Computer Networks 38 19 12/3/13 Home Network (3) •  Master key is from password; nonces for freshness –  KS lets client talk to AP; KG lets AP talk to all clients Computer Networks 39 Enterprise Network •  Network has authen7ca7on server •  Each client has own creden7als •  AP lets client talk to auth. server –  Grants network access if successful (wire) Client Computer Networks AP Network Auth. Server 40 20 12/3/13 Introduc7on to Computer Networks Web Security (§8.9.3, §8.5) Computer Science & Engineering Goal and Threat Model •  Much can go wrong on the web! –  Clients encounter malicious content –  Web servers are target of break- ins –  Fake content/servers trick users –  Data sent over network is stolen … Internet Client Computer...
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