Anonymity

What is a VPN?

a Virtual Private Network that establish a connection towards a (trusted) server and all your internet traffic is encrypted in this channel

What is OpenVPN?

Open source software for creating a VPN

What library does OpenVPN use?

It uses OpenSSL to deal with key exchange via SSL/TLS

What security protocol does OpenVPN follow?

A custom one based on TLS.

Can ports and protocols be changed with OpenVPN? Why ? Why not?

Yes for flexibility to avoid limitations

How do clients authenticate an OpenVPN server?

A certificate rather than a shared secret.

Why are VPNs useful?

Used to access sensitive service or data in a company from outside

Used to anonymize the traffic as the ISP (Internet Service Provider) will no longer know which websites you surf as it will only see a connection towards the VPN server

Used to simulate your current position to the one of the VPN server

Useful for banned website in specific Countries

Useful to access media content of another Country (like pay-per-view TV, etc…)

What is a different approach to anonymity other than VPNs?

Mix networks

What were mix networks originally designed for?

Anonymous email but have since been generalised for TCP traffic.

What influential ideas did mix networks bring about?

Onion routing

Traffic mixing

Dummy traffic (a.k.a. cover traffic)

How does onion routing protect anonymity?

Messages are encrypted in multiple layers, each removed by a proxy node in sequence, obscuring the sender and receiver.

How is return traffic handled in mix networks?

The sender pre-establishes keys along the return path; messages are re-encrypted in reverse.

What are the key components of the Tor network?

Guard (input) nodes - know the identity of sender

relay nodes - used to route messages (made up of advertised nodes and bridge nodes [those not listed in the directory server])

and exit nodes - can see traffic if unencrypted

What makes Tor different from basic mix networks?

It considers bandwidth for relay selection and includes hidden services.

What are Tor directory servers?

They store and manage the status of Tor nodes.

What are Tor hidden services?

Services accessible only within the Tor network, hiding both the client and server IP addresses as well as the servers DNS name.

How does a user connect to a hidden service in Tor?

Using an onion address, introduction points, and rendezvous points.

How is voter authentication done in Estonian e-voting?

Via an ID card and a PIN pad using two separate keys: one for authentication and another for confirming the vote.

How is vote anonymity ensured?

Encrypted vote is signed (blue envelope), then placed in a digital signature envelope (yellow), separating identity from the vote.

What is homomorphic encryption?

Encryption allowing computation on ciphertexts without decrypting them.

How does homomorphic encryption benefit e-voting?

Votes can be counted without revealing individual choices, preserving voter privacy.

What are some examples of hidden services?

Tor Mail, Tor Char

DuckDuckGo

Wikileaks