SLIDE 1
Lightweight Authentication for Email (and Web?)
Ben Adida
ben@mit.edu
PAW/DIG Meeting June 30th, 2005
(joint work with Susan Hohenberger and Ronald L. Rivest)
Lightweight Authentication for Email (and Web?) Ben Adida - - PowerPoint PPT Presentation
Lightweight Authentication for Email (and Web?) Ben Adida - - PowerPoint PPT Presentation
Lightweight Authentication for Email (and Web?) Ben Adida ben@mit.edu PAW/DIG Meeting June 30th, 2005 (joint work with Susan Hohenberger and Ronald L. Rivest) Distributed Phishing Friends and Colleagues Jakobsson & Young 2005
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Distributed Phishing
- Friends and Colleagues
- Jakobsson &
Young 2005
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DNS
foo.com MX Record mail.foo.com Alice Bob
wonderland.com
- utgoing
mail server
mail.foo.com
incoming mail server MX
2 1 3 4
SMTP Today
Review
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No Proof of Origin
Review
Alice Bob
wonderland.com
- utgoing
mail server
mail.foo.com
incoming mail server
phish.com
?
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ID-Based Crypto
Review
keyserver
Alice Bob
MSK MPK "bob@foo.com" PKbob SKbob
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ID-based Domains
Bob Alice
New
SKalice@wonderland.com SKbob@foo.com MPKwonderland.com MPKfoo.com
wonderland.com
keyserver
MSKwonderland.com
foo.com
keyserver
MSKfoo.com
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DNS to distribute Master Public Keys
New
wonderland.com key server
MSKwonderland.com DNS
wonderland.com foo.com
MPKwonderland.com MPKfoo.com
Publish
[DomainKeys]
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Email-Based Authentication
[Gar2003] New
Alice
wonderland.com
incoming mail server
wonderland.com
keyserver
MSKwonderland.com SKalice@wonderland.com
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Tweaks & Optimizations
- Key Revocation - expiration date in the ID string:
- Domain Policies
immediate deletion of spoofed emails.
- Alternate Keyserver
bootstrap individual users. Different Trust.
“ben@mit.edu - 2005-04-26”
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Repudiability
Bob Alice
Eve
Repudiability is about Privacy
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Ad-Hoc Group Sigs
From: Alice To: Bob Subject: Account Your monthly balance is available at: http://wonderbank.com Signed:
Alice or Bob
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Hijacking Keys for AHGS
I signed this message, OR I have your secret key
- Signature or Encryption key
- Factoring-, DL-, BM-based algorithms
- All known keypairs work!
[AHR2005]
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foo.com Network
foo.com
key server
Bob
Wonderbank.com Network
wonderbank.com
key server
Alice
Putting it All Together
MPKfoo
3 4
"bob@foo.com" PKB
SKA
2
From: Alice To: Bob Subject: Account Your monthly balance is available at: http://wonderbank.com Signed:
Alice or Bob
5
PUBLISH
DNS
wonderbank.com foo.com
MPKbank
PUBLISH
MPKfoo
1 1
MPKbank
6 7
"alice@wonderbank.com" PKA
8
9
[AHR2005]
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Web Authentication?
Web Server PK
Alice Request for Authentication Request for Resource Signature on Nonce, Repudiable Against PK
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