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43 lines
3.3 KiB
Markdown
43 lines
3.3 KiB
Markdown
# Chapter 12: Using Tor
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In this section will talk about Tor network and how to use its services that are now available courtesy of [Bitcoin Standup](https://github.com/BlockchainCommons/Bitcoin-Standup-Scripts)
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## 1. Tor network
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Tor is a low-latency anonymity and overlay network based on onion routing and path-building design for enabling anonymous communication. Tor is free and open-source software and the name derived from the acronym for the original software project name "The Onion Router". The Tor Project, Inc. is a Massachusetts-based research-education nonprofit organization founded by computer scientists Roger Dingledine, Nick Mathewson and others. The Tor Project is primarily responsible for maintaining software for the [Tor anonymity network](https://www.torproject.org/)
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## 2. How it works
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When a user wants to connect to an Internet server Tor tries to build a path formed by at least three Tor nodes relays called Guard, Middle and Exit. In this building path creates a circuit that negotiates encrypted symmetric keys,that while the message goes along the circuit, each relay strips off its layer of encryption. In this way the message arrives at the final destination in its original form and each party only knows the previous and the next hop and cannot determinate origin or destination.
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The basic architecture of the Tor network is made up of the following components:
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* Tor Clients (OP or Onion Proxy): A Tor client installs local software considered as an onion proxy, which packages the application data into cells the same size (512 bytes) that it sends to the Tor network. A cell is the basic unit of Tor transmission.
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* Onion node (OR or Onion Router): Onion nodes transmit cells coming from the Tor client and server. There are three types of onion nodes:
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input (Guard), intermediate nodes (Middle), and output nodes (Exit).
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* Directory servers: Directory servers store the information of onion routers and onion servers (hidden services), such as their
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public keys.
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* Onion servers (hidden servers): They support TCP applications as a service web or IRC service
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### Clear internet connection
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When a user connects to an Internet Server it shares it's ip address, location, operating system and other details with the server. Using a data-network packet analyzer like tcpdump we see how connection is established.
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```
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$ tcpdump
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```
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Output
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```
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20:58:03.804787 IP bitcoin.36300 > lb-140-82-114-25-iad.github.com.443: Flags [P.], seq 1:30, ack 25, win 501, options [nop,nop,TS val 3087919981 ecr 802303366], length 29
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```
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When a user connects to an Internet Server using tor it create a circuit using three relay nodes that only knows previous and the next hop. This is the output first server or Guard node.
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```
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21:06:52.744602 IP bitcoin.58776 > 195-xxx-xxx-x.rev.pxxxxxm.eu.9999: Flags [P.], seq 264139:265189, ack 3519373, win 3410, options [nop,nop,TS val 209009853 ecr 3018177498], length 1050
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21:06:52.776968 IP 195-xxx-xxx-x.rev.pxxxxxm.eu.9999 > bitcoin.58776: Flags [.], ack 265189, win 501, options [nop,nop,TS val 3018177533 ecr 209009853], length 0
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```
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* [12.1: Verifying Your Tor Setup](12_1_Verifying_Your_Tor_Setup.md)
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* [12.2: Changing Your Bitcoin Hidden Services](12_2_Changing_Your_Bitcoin_Hidden_Services.md)
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* [12.3: Adding SSH Hidden Services](12_3_Adding_SSH_Hidden_Services.md)
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