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Security and Authentication (continued)

Security and Authentication (continued). CS-4513 D-Term 2007

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Security and Authentication (continued)

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  1. Security and Authentication(continued) CS-4513D-Term 2007 (Slides include materials from Operating System Concepts, 7th ed., by Silbershatz, Galvin, & Gagne, Modern Operating Systems, 2nd ed., by Tanenbaum, and Distributed Systems: Principles & Paradigms, 2nd ed. By Tanenbaum and Van Steen) Authentication (review)

  2. Review • Identity 2.0 Video • Humorous presentation about a real problem • Some basics about cryptography • Private key systems • Public key systems • A (very) brief overview of Kerberos • Tanenbaum & Van Steen, §9.2.4 Authentication (review)

  3. Class Discussion(laptops closed, please!) • What is difference between distributed authentication methods in • Grapevine • Kerberos • Identity 2.0 • I.e., • Who gets involved? • What is flow of authentication request? • What is chain of trust? • Etc. Authentication (review)

  4. Class Discussion (continued)(laptops closed, please!) • Grapevine • User presents credentials to service • Service validates credentials with any registration server • Kerberos • User authenticates self with AS; asks TGS for ticket to talk with service • User presents ticket to service; service trusts ticket • Identity 2.0 (goal) • User authenticates once with authority, gets reusable credential • User presents credential to service; service can test validity of credential by inspection Authentication (review)

  5. Class Discussion #2(laptops still closed, please!) • Speculate how an authentication system might be implemented to be consistent with Identity 2.0 goals • Based on what we learned last time about • Public Key cryptography • Various authentication protocols Authentication (review)

  6. Class Discussion #2 (continued)(laptops still closed, please!) • Some thoughts on credential • Encrypted with private key of trusted authority • Anyone trusting the authority can decrypt and read it • Contains public key of authenticated user • Only the authentic user can understand a message encrypted with this key Authentication (review)

  7. Class Discussion #2 (continued)(laptops still closed, please!) • Possible protocol • User sends request (in clear) with credential • Service inspects credential, replies in user’s public key with • Nonce • Service’s credential • Challenge-response protocol continues to establish • Mutual confidence in identities • Session key Authentication (review)

  8. Result • Authentication service does not participate in connection at all • Session key established without previously sharing any key • Trust based on original authenticator • Many issues about other aspects of identity Authentication (review)

  9. Questions Next Topic Authentication (review)

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