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Authentication Approaches

Authentication Approaches. Phillip Hallam-Baker VeriSign Inc. Why?. Authentication + Authorization = Access Control Authentication IP Address Cryptographic Authorization Email Address Whitelists [alice@example.com] Domain Whitelists [example.com] Payment [$0.01 stamp].

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Authentication Approaches

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  1. Authentication Approaches Phillip Hallam-Baker VeriSign Inc.

  2. Why? Authentication + Authorization = Access Control • Authentication • IP Address • Cryptographic • Authorization • Email Address Whitelists [alice@example.com] • Domain Whitelists [example.com] • Payment [$0.01 stamp]

  3. How Strong is Enough? • LIST Kiddies • Like a script kiddie but they pay for the mailing list • Actually a spam victim, they get worthless service in return • SPAM Houses • Will adapt to heuristic authentication approaches • But it will cost them

  4. PKI • Infrastructure exists to • Ensure that a party owns the purported domain name • Ensure that legal process can be served on the certificate holder • With a high (but not absolute) degree of confidence SECURITY IS RISK CONTROLNOT RISK ELIMINATION

  5. Deployment Argument • Authentication Compliments Filtering • Network effect, aka Chicken and Egg problem • Avoid false positives • Without creating backdoors • ‘Allow all mail from hotmail.com, they use rate limiting’ • Allows more aggressive criteria • Cryptographic Authentication is robust • Asymmetric work factor • No viable counter-strategies

  6. Problem – Email Insecure by Default • Downgrade attack • I can tell a signed message comes from the sender • I cannot assume an unsigned message is false • Key is to know the security policy of the domain

  7. DNS Based Security Policy • Reverse IP look up • Some Current Use • Only demonstrates that the IP address has been assigned • IPv4 address exhaustion will make this uninteresting • Configuration problem – servers handling 1000’s of domains • Many ISPs do not delegate reverse DNS as they should • Get a new ISP is an idiotic deployment strategy

  8. Forward DNS • Address based authentication • RCPT From [Vixie] • Reverse MX • Pro: Lightweight, almost costless • Pro: Obsoletes most existing spamware • Con: Could be vulnerable to new spamware • Con: Some operational issues • Con: Only works if mail from domain is relayed

  9. Generalized Security Policy • Security Policy Advertisement Mechanism • Advertise any form of security policy • ALWAYS comes from address X, Y or Z • OPTIONAL uses STARTTLS, cert root has SHA1 P • OPTIONAL uses S/MIME, cert root has SHA1 Q • OPTIONAL uses PGP, validate against XKMS R • NEVER uses NULL Authentication • Can be generalized to other protocols • IPSEC, SSH, NNTP, POP, IMAP…

  10. This is Just a Bug We Are going to FIX IT

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