Anonymity:
- what is anonymity (with example from the course feedback form they submitted last week)
- what is unlinkability (with example of their "hand-written” mid-sem and "hand-written” course feedback form)
- why are these sometimes useful in Internet (censorship, profiling), different cases of source anonymity, destination anonymity, anonymity from third party like government
- IP anonymity is the focus: application level HTTP(S), DNS etc. needs to be separately taken care of

Single proxy:
- the concept of indirection with one proxy (e.g. HideMyAss VPN to access netflix)
- issues with single proxy: subpoena, that IP censored

Onion:
- distribute the proxy across many nodes, this is where “distributed systems” is coming in aid for “anonymity”
- but if all proxies know about the whole network, each can suffer subpoena
- proxies need to know just the part needed for it, previous and next hop
- “onion”, open only one layer of a message at each proxy

RSA for onion:
- public key crypto, RSA, public key, secret key basics
- use RSA for onion routing, use public keys of proxies for the successive layers
- downsides: speed, size of message, forward secrecy (explain what is it)

Symmetric key for onion:
- how to set up a symmetric key: diffie hellman basics (e.g. riju needs to set up a key with dawei, but they cannot go to corridor to decide that, the whole class will listen)
- AES basics and advantages in speed and size over RSA
- forward secrecy, easier to generate for each communication that create public-secret key pairs in PKI

Demo: Viktor
- Tor browser on laptop
- the user interface remains the same: an http(s) request
- the circuit which gets created
- the IP seen by the website (it thinks Viktor is in Romania)
- example directory of Tor nodes

Time diagram of Tor workflow
- the commands to create circuit, web requests and transfers, teardown circuits
- “authenticated" Diffie Hellman, using public key of routers

Hidden services
- Rendevouz point (e.g. date a guy for the first time, do not want to tell home address, fix meeting at university, I know route from home to uni, he knows route from his home to uni)
- show how it works in Tor

Demo: Viktor
- awesome hidden services: murderers and rapists on hire
- another Tor like network I2P, with special support for hosting services within an anonymity network
- Viktor mentioned the conflict between anonymity and trust/accountability, and that Krishna will discuss these more in next classes
- we mentioned good reasons why someone might need a hidden service (wikileaks or prevent a dos attack)

Attacks on Tor:
- just told them to see in the paper
- one simple example of traffic analysis attack, how it works: http://dl.acm.org/citation.cfm?id=1059390
- mentioned many attacks in the paper are outdated and new attacks and defenses keep coming up

Final demos: Viktor
- freenet: a DHT to upload and download data anonymously (connecting the DHT lectures to today’s class)
- tribler: a bit-torrent based on Tor (connecting last class to today’s class)