Merge branch 'i2p' of https://github.com/prayank23/Learning-Bitcoin-from-the-Command-Line into prayank23-i2p

Author: shannona

15_0_Using_i2p.md

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+# Chapter 15: Using i2p
+
+The Invisible Internet Project (I2P) is a fully encrypted private network layer. It uses a distributed [network database](https://geti2p.net/en/docs/how/network-database) and encrypted unidirectional tunnels between your and your peers.
+
+Basic differences between Tor and i2p:
+
+|  | Tor | i2p |
+| :---         |     :---:      |          ---: |
+| Routing   | [Onion](https://www.onion-router.net/)     | [Garlic](https://geti2p.net/en/docs/how/garlic-routing)    |
+| Network Database     | Trusted [Directory Servers](https://blog.torproject.org/possible-upcoming-attempts-disable-tor-network)       | [Distributed network database](https://geti2p.net/en/docs/how/network-database)      |
+| Relay     | **Two-way** encrypted connections between each Relay       | **One-way** connections between every server in its tunnels      |
+| Hidden services     | Slow       | Fast      |
+
+Read more: https://geti2p.net/en/comparison/tor
+
+It is not installed by [Bitcoin Standup](https://github.com/BlockchainCommons/Bitcoin-Standup-Scripts) right now as i2p support was recently added in Bitcoin core. However, you can try it manually by following the steps mentioned in [Section One](15_1_i2p_service.md).
+
+## Objectives for This Chapter
+
+After working through this chapter, a developer will be able to:
+
+  * Run Bitcoin Core as an I2P (Invisible Internet Project) service
+
+Supporting objectives include the ability to:
+
+  * Understand the i2p Network
+  * Learn difference between Tor and i2p
+
+## Table of Contents
+
+* [Section One: Bitcoin Core as an I2P (Invisible Internet Project) service](15_1_i2p_service.md)

15_1_i2p_service.md

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+# 15.1: Bitcoin Core as an I2P (Invisible Internet Project) service
+
+Users should consider different trade-offs involved in using i2p with other networks in Bitcoin Core for better privacy:
+
+- Sybil Attacks and Network Partitioning is possible with `onlynet=i2p`
+- Running Onion service with i2p service is experimental for now.
+- For maximum privacy, it is preferable to disable accepting incoming connections.
+
+Read more: https://bitcoin.stackexchange.com/questions/107060/tor-and-i2p-tradeoffs-in-bitcoin-core
+
+Follow the below steps to run Bitcoin Core i2p service:
+
+1. You can install `i2pd` on Ubuntu with below commands:
+
+   ```
+   sudo add-apt-repository ppa:purplei2p/i2pd
+   sudo apt-get update
+   sudo apt-get install i2pd
+   ```
+
+   For installing on other OS: https://i2pd.readthedocs.io/en/latest/user-guide/install/
+
+2. Then [run](https://i2pd.readthedocs.io/en/latest/user-guide/run/) it and check if its running:
+
+   ```
+   $ sudo systemctl start i2pd.service
+   ```
+
+   You should see it running on port 7656:
+
+   ```
+   $ ss -nlt
+
+   State   Recv-Q   Send-Q     Local Address:Port      Peer Address:Port  Process
+
+   LISTEN  0        4096           127.0.0.1:7656           0.0.0.0:*
+   ```
+
+3. Add the following lines in `bitcoin.conf`. Config logging option `debug=i2p` is used to have additional information in the debug log about your I2P configuration and connections (Default location on Linux: ~/.bitcoin/bitcoin.conf):
+
+   ```
+   i2psam=127.0.0.1:7656
+   debug=i2p
+   ```
+
+5. Restart `bitcoind`
+
+   ```
+   $ bitcoind
+   ```
+
+6. Check `debug.log`if i2p was setup correctly or any errors printed in logs.  I2P address is mentioned in the logs and ends with _b32.i2p_:
+   ```
+   2021-06-15T20:36:16Z i2paccept thread start
+   2021-06-15T20:36:16Z I2P: Creating SAM session with 127.0.0.1:7656
+
+   2021-06-15T20:36:56Z I2P: SAM session created: session id=3e0f35228b, my address=bmwyyuzyqdc5dcx27s4baltbu6zw7rbqfl2nmclt45i7ng3ul4pa.b32.i2p:18333
+   2021-06-15T20:36:56Z AddLocal(bmwyyuzyqdc5dcx27s4baltbu6zw7rbqfl2nmclt45i7ng3ul4pa.b32.i2p:18333,4)
+   ```
+
+7. Confirm `i2p_private_key` was created in Bitcoin Core data directory. The first time Bitcoin Core connects to the I2P router, its I2P address (and corresponding private key) will be automatically generated and saved in a file named *i2p_private_key*:
+   ```
+   ~/.bitcoin/testnet3$ ls
+
+   anchors.dat  chainstate         i2p_private_key  settings.json
+   banlist.dat  debug.log          mempool.dat      wallets
+   blocks       fee_estimates.dat  peers.dat
+   ```
+
+8. `bitcoin-cli -netinfo` or `bitcoin-cli getnetworkinfo`returns i2p address:
+
+   ```
+   Local addresses
+   bmwyyuzyqdc5dcx27s4baltbu6zw7rbqfl2nmclt45i7ng3ul4pa.b32.i2p     port  18333    score      4
+   ```
+
+## Summary: Bitcoin Core as an I2P (Invisible Internet Project) service
+
+It is always good to have alternatives for privacy and not depend only on Tor to run Bitcoin Core as hidden service. Since i2p was recently added in Bitcoin Core, less people use it, experiment with it and report bugs if you find any issues.
+
+> :information_source: **NOTE:** _i2pd_ (C++) is different from _i2prouter_ (Java), you will need `i2pd` for Bitcoin Core.
+
+Move on to "Programming with RPC" with [Chapter Sixteen: Talking to Bitcoind with C](16_0_Talking_to_Bitcoind.md).
+
+Or, if you're not a programmer, you can skip to [Chapter Nineteen: Understanding Your Lightning Seutp](https://github.com/BlockchainCommons/Learning-Bitcoin-from-the-Command-Line/blob/master/19_0_Understanding_Your_Lightning_Setup.md) to continue your command-line education with the Lightning Network.