1. Ceremonies (in 3 minutes)
Carl M. Ellison
Microsoft
16 August 2005

2. Network Protocol A B C D

3. Ceremony
Carol
Alice
Bob A B C D

4. HTTPS MITM Protocol Legitimate MITM User PC Channel Setup a b c d
HTTP(S)
HTTP(S) PC
Channel
Setup a b c d

5. HTTPS MITM Ceremony Legitimate MITM User PC a b Channel Setup c d e f
HTTP(S)
HTTP(S) PC a b
Channel
Setup c d e f g

6. Conclusion
Design a great protocol, prove it secure; add a user, it’s insecure
Design a great protocol, prove it secure; embed it in a larger protocol, it’s insecure
These two observations aren’t just similar
…with Ceremonies, they are the same statement.

7. Think Ceremonies
Carol
Alice
Bob A B C D