Lecture 19: TLS (Transport Layer Security)

• Slides
• Playlist (length: 49:59)

Intro to TLS

(True/False) TLS sits on top of UDP

False - TCP

TLS on the Web

(True/False) You use TLS when you visit http://foo.com

False. Only sites with https are visited using TLS

RSA TLS

In RSA TLS, which party generates the Premaster Secret? How is it sent to the other party?

The client generates the Premaster Secret and uses the server’s public encryption key to encrypt and send it to the server.

Ephemeral Diffie Hellman TLS

(True/False) In DH TLS, one party could force the Premaster Key to be a specific value

False. Both parties contribute randomness

DH vs. RSA TLS and Forward Secrecy

(True/False) RSA TLS can be made to have forward secrecy by making sure to pick a new Premaster Secret on each handshake

False. The problem is the server’s static asymmetric key not the PS. The PS is always randomly generated.

Certificates

(True/False) Even if an attacker is a MiTM, they can't fake a valid certificate

True. This follows from the properties of signatures