11 web security httpsssl applied crypto dns security

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Unformatted text preview: just made the first one harder! –  802.11 is more secure against eavesdropping in that the risk of successful aNack is lower. But it is not “secure”. Threat Model Old WiFi (WEP) New WiFi (WPA2) Break encryp7on from outside Very easy Very difficult Guess WiFi password OCen possible OCen possible Get password from computer May be possible May be possible Physically break into home Difficult Difficult Computer Networks 7 Topics •  •  •  •  •  •  •  •  •  This Threat models 7me Confiden7ality Crypto Authen7ca7on Wireless security (802.11) Web security (HTTPS/SSL) Applied crypto DNS security Virtual Private Networks (VPNs) Firewalls Distributed denial- of- service Connec7vity Computer Networks 8 4 12/3/13 Goal and Threat Model •  Goal is to send a private message from Alice to Bob –  This is called confiden7ality •  Threat is Eve will read the message –  Eve is a passive adversary (observes) ?? I♥networks Bob Alice Eve Computer Networks 9 Encryp7on/Decryp7on Model •  Alice encrypts private message (plaintext) using key •  Eve sees ciphertext but can’t relate it to private message •  Bob decrypts using key to obtain the private message Plaintext I♥networks Alice Encrypt Key Computer Networks Eve Hi there Ciphertext Network Plaintext I♥networks Decrypt Bob Key 10 5 12/3/13 Encryp7on/Decryp7on (2) •  Encryp7on is a reversible mapping –  Ciphertext is confused plaintext •  Assume aNacker knows algorithm –  Security does not rely on its secrecy •  Algorithm is parameterized by keys –  Security does rely on key secrecy –  Must be distributed (Achilles’ heel) Computer Networks 11 Encryp7on/Decryp7on (3) Two main kinds of encryp7on: 1.  Symmetric key encryp7on », e.g., AES –  Alice and Bob share secret key –  Encryp7on is a bit mangling box 2.  Public key encryp7on », e.g., RSA –  Alice and Bob each have...
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