# legochain ## What is this? This simple program implements a working blockchain class (*based on block mining with a difficulty level*) plus a very simple "peer to peer" protocol that enables two or more servers to talk to each other and send/receive their blockchains, based on TCP sockets. This is a simple project with the following goals, either: ### Goal A To show newcomers to Common Lisp, an example of how to implement something not so simple but not too complex, like a blockchain, that would involve the use of: - Cryptography, using [ironclad](https://github.com/sharplispers/ironclad) - Regular expressions, using [cl-ppcre](https://edicl.github.io/cl-ppcre/) - Sockets, using [usocket](https://github.com/usocket/usocket) - [The Common Lisp Object System](http://www.gigamonkeys.com/book/object-reorientation-generic-functions.html), specifically the use of generic functions and multiple dispatch, to make the code a bit simpler. The code is written with as many comments as possible, and is as clear as I can manage to. The aim was not performance, nor production-quality, but educational value. You can start by taking a look at [legochain.lisp](legochain.lisp) and then to [peertopeer.lisp](peertopeer.lisp) ### Goal B - To show seasoned CL developers who still haven't yet found out what is a blockchain, block mining, and the "nonce" values, a simple answer by looking at the code. ## Supported features - Add any kind of data to the block's payload. You only need to define the encoding for the payload using `conspack:defencoding` (see the code) - Verification of one blockchain against other, rejecting invalid blockchains - Verification of the continuity (soundness) of each blocks' hash value and sequence value Peer to peer supported operations: - Send blockchain to peer - Request blockchain from peer - Say "hi" to peer. You can start many peers from your same machine so you can experiment adding more features to the code. ## How to install (for newcomers to CL) - Install [Portacle](https://portacle.github.io/), the portable Common Lisp environent. - Clone this project into the *projects* subdirectory under the portacle root directory, so you have it into `/portacle/projects/legochain`. - Start portacle - Write `(ql:quickload "legochain")` to load the program. - All the functions are in package "legochain". - Try `(legochain::servers-test 9000 9001)` to make two blockchain servers talk to each other (a simple demo.) ## Author Flavio Egoavil aka D e f u n k y d r u m m e r License MIT # Hacking I'm always open to pull requests that can make the code more readable or more educational!