Bc. Oldřich FaldíkBc. Tomáš PavlackýBc. Ondřej Matulík

24. 3. 2014

Tor – anonymity online

• Open source project• Tails• Orbot• Tor Browser

• Provides anonymity• Used by dissidents in non-democratic

countries, military agents, activists, whistleblowers

Tor

The Tor network

• Several thousand nodes• 4500 nodes• Two types of nodes

• Exit nodes• Non-exit nodes

STEPS:1. identify sender and recipient2. get list of available nodes3. create a circuit to recipient4. determine exit node to interconnects Tor network

and external internet domains

Principles of route formation

MESSAGE

Data Encryption

MESSAGE

Data Encryption

MESSAGE

Data Encryption

MESSAGE

Data Encryption

MESSAGE

Data Encryption

Encryption Methods

• Communication node – node and client – node: • TLS (Transport Layer Security)

• Neighbour routers in chain (data path):• AES-128-CTR (AES with a 128 bit key in

counter mode)

Pros x cons

• Pros:• completely free• encrypts all traffic

• Cons:• configuration is not trivial• perfomance is unpredictable• not suitable for p2p applications

Thank you for your time