Terms of service: governed by the laws of Luxembourg.Login server – Stores Skype id’s, passwords, and buddy lists – Used at login for authentication.Calls between traditional telephone and internet devicese.– A Skype client (SC) that has public IP address, ‘sufficient’ bandwidth, CPU and memory 61.3% of US home internet users use broadband ().Message exchange with the login server during login

Challenges include dealing with NATs, firewalls and scalability 9īased on slides by Baset and Schulzrinne (Infocom 06).Login server Buddy-list server Servers for SkypeOut and SkypeIn Anonymous call minutes statistic gathering – Has peer-to-peer features that will look familiar – Motivation – Architectures – TOR – Skype Support pc-to-pc, pc-to-phone, phone-to-pc VoIP and IM client communication.– Directory servers’ keys ship with Tor code slide 7 “Sybil attack”: attacker creates a large number of relays.– Control how new nodes join the network Directory servers – Maintain lists of active relay nodes, their locations, current public keys, etc.– Encourages people to set up their own routers – More participants = better anonymity for everyone Also want end-to-end encryption – not done by Tor.Tor router doesn’t need root privileges.Many applications can share one circuit – Multiple TCP streams over one anonymous connection.Client applications connect and communicate over established Tor circuit.Client proxy extends the circuit by establishing a symmetric session key with relay node #3.Client proxy extends the circuit by establishing a symmetric session key with relay node #2.Really an overlay – not pure peer-to-peer Based on slides by Vitaly Shmatikov slide 3.Easy-to-use client proxy, integrated Web browser – Not like FreeNet – no data “in” TOR.Running since October 2003 – Thousands of relay nodes, 100K-500K? of users.– – Specifically designed for low-latency anonymous Internet communications All data sent over the circuit is encrypted.Client proxy establish a symmetric session key and circuit with relay node #1 A = K(B) k.Peer-to-peer – Motivation – Architectures – TOR – Skype.Overview 18-345: Introduction to Telecommunication Networks Lectures 18: Delivering Content Web, Peer-Peer, CDNs

Skype tor proxy