Update 08 Mar 2013
Release 0.1
Update 28 Mar 2013
Merged with 0.8.1
Update 04 Jul 2013
Release 0.2
Improved I2P related code.
Some GUI indicators are added: number of I2P-connections, I2P/non-I2P mode, static/dynamic I2P-address
An I2P options tab added. (Settings - Options... - I2P)
Now you could generate a new I2P-address or could see your current I2P-address in GUI.
Update 11 Jul 2013
Migrated to 0.8.3.
Update 13 Sep 2013
Migrated to 0.8.5.
Update 24 Dec 2013
Migrated to 0.8.6.


References:
Source files:
https://github.com/VirtualDestructor/bitcoin-qt-i2p
Binaries for Windows and Linux x64:
https://sourceforge.net/projects/bitcoinqti2p
Original theme in Russian subforum:
https://bt.irlbtc.com/view/138588.0

(Sorry for my bad English. If someone has a better translation of this post, please pm me)
My project is a patch for Satoshi-client (aka bitcoin-qt/bitcoind). For the present it is more like a Proof-of-Concept than finished application. On the other hand the vanilla bitcoin-client is still beta and nobody worries about that. My client can work in i2p-net using SAM bridge without any third-party libraries. Blocks database is compatible with vanilla client, so you may copy the database from your usual client instead of downloading whole database again.



Installation on Linux (on Ubuntu 12.04 for example):
1) add ppa for i2p and bitcoin

2) update

3) install packages (java will be installed by dependencies)

4) edit this fileetc/default/i2p under root

5) now run i2p

Installation on Windows:
1) download an i2p distribution kit from official site only: http://www.i2p2.de/download
2) i2p installer will notify you if Java is not installed on your system. If so you should download Java from official site too http://java.com/download/
3) first install Java, then install I2P
4) go to Control Panel - Administrative tools - Services, find "I2P" and check it is running (if it isn't running you should run it)

Running bitcoin in i2p (both Windows and Linux):
1) after I2P was running you should wait a few minutes while i2p is integrating in the network
2) in your browser open the page http://127.0.0.1:7657/configclients. If the page is unavailable that mean I2P was not running (maybe some errors were occured). If the page opens you should press "Start" button near "SAM application bridge" item and enable a checkbox in column "Run at Startup?" After that press "Save Client Configuration" button.
3) delete (or rename) file peers.dat, it's located at C:\Documents and Settings\<YourUserName>\Application data\Bitcoin (for Win XP)  | C:\Users\<YourUserName>\Appdata\Roaming\Bitcoin (for Vista and 7) | ~/.bitcoin (for linux).
You must to do this because serialization format of network addresses is incompatible between the vanilla client and my patch. You need to do this procedure only once before the first start of the patched client. The patched client will make his own peers.dat with required format. Warning! If you leave this file at his place it cause a deadlock of the patched client.
4) download the patched executable files or compile the executable files by yourself and run it
If you want to deal with i2p-net only you should specify option -onlynet=native_i2p as shown above. If you want to deal with both i2p and ip(usual internet) don't specify this option at all, in this case you client will be a gate between i2p-segment of bitcoin-net and the rest net.

Notes:
If you want to help other bitcoin users in I2P you may send me or publish here your dest-hash or b32-address and I will add them to the sources as seed-node in a next release. But if you want this you should run your wallet with a permanent i2p-address (see section "Starting wallet with a permanent I2P-address" below)

Changes in command line arguments:
1) New command line options are added:
2) New possible value for "-onlynet" option is added:
3) In all options required IP-addresses now you can specify destination hash: <512 symbols>AAAA or b32-address: <52 symbols>.b32.i2p


Compatibility:
1) All of the rest options (except of described above) is not changed and working as they did before
2) Database-file peers.dat is not compatible in both way, neither from vanilla client to my patch, not from my patch to vanilla client. This file must be deleted (or renamed) before using my patch and before going back to vanilla client. This file doesn't contain any important data, so you don't need to back up it.
3) all the rest of databases is compatible with vanilla client.
4) Full backward compatibility of the bitcoin-protocol! Patched client works fine with unpatched vanilla clients. Changes in the protocol are appeared only if both clients are patched.

Starting wallet with a permanent I2P-address:
By default if you don't specify -mydestination parameter the patched wallet generates random i2p-destination. It anonymizes your work with bitcoin even more than before. Especially if you use a new bitcoin-address for each transaction. But if you want to help network by publishing you i2p-address or you just like some i2p-address you have to run wallet with permanent i2p-address. You should specify a full destination in the "mydestination" option for that. Full destionation consists of base64 destionation (b32-address is not allowed here!) and your private tunnel key.
Example:
Run from command line:

Or you may use your config-file (bitcoin.conf):

The first 516 symbols (SVAxp......~vaZfIQP6AAAA) are public key. This key is a base64 i2p-address (aka dest-hash). The rest symbols are private key. If you want to use some i2p-address you need to know its private key. If you publishes you private i2p-key anyone can use your i2p-address. So keep in secret your private key. This program don't send your private key, it uses your key only to open i2p-tunnel. A simplest way to generate your own I2P-address is running the patched client with option -generatei2pdestination. A generated address with a private key will be shown and you will can copy it to your config-file and publish it.

Building from the sources on Linux:
0) Install all necessary libraries for bitcoin. No additional dependencies are needed.
1) Go to a root directory of the project and run 1.build-unix.sh

Crosscompillation for Windows on Linux:
0) Install mingw32
1) Download and unpack dependencies using script 1.env-setup.sh
2) Build dependencies by script 2.build-deps.sh
3) Build bitcoin with i2p-patch using 3.build-linux-mingw.sh

All builded binaries will be located at <directory with project>/release.
I don't have native windows build scripts, because I use crosscompilation as shown above.

This program is provided "as is" without any warranties.

If you like my project support further developing 1JTtvgy5CzwnsRj3vtHACdyKWxgTnYn754