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Uwedu as usual replies include signatureskeys client

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Unformatted text preview: are called CAs (Cer7ficate Authori7es) I cer7fied the ABC website! Computer Networks 49 PKI (2) •  Need public key of PKI root and trust in servers on path to verify a public key of website ABC –  Browser has Root’s public key –  {RA1’s key is X} signed Root –  {CA1’s key is Y} signed RA1 –  {ABC’s key Z} signed CA1 Computer Networks I cer7fied the ABC website! 50 25 12/3/13 PKI (3) •  Browser/OS has public keys of the trusted roots of PKI –  >100 root cer7ficates! –  That’s a problem … –  Inspect your web browser Cer7ficate for wikipedia.org issued by DigiCert Computer Networks 51 PKI (4) •  Real- world complica7on: –  Public keys may be compromised –  Cer7ficates must then be revoked •  PKI includes a CRL (Cer7ficate Revoca7on List) –  Browsers use to weed out bad keys Computer Networks 52 26 12/3/13 SSL3 Authen7ca7on (2) Cer7ficate lets Alice check Bob Switch to Alice’s session key Encrypted data Computer Networks Nego7ate ciphers, send cer7ficate, … Real Bob can compute session key Encrypted data 53 Introduc7on to Computer Networks DNS Security (§8.9.2) Computer Science & Engineering 27 12/3/13 Goal and Threat Model •  Naming is a crucial Internet service –  Binds host name to IP address –  Wrong binding can be disastrous … bank.com? Internet Computer Networks 55 Goal and Threat Model (2) •  Goal is to secure the DNS so that the returned binding is correct –  Integrity/authen7city vs confiden7ality •  ANacker can intercept/tamper with messages on...
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