Video Demo: https://youtu.be/HuzzJ8RMxxg
An exercise to better understand the workings of blockchains and cryptocurrencies. Completely made with python and a sqlite3 database, implements the key features of a blockchain, such as:
- Distributable: every block must exist and be in its place in order for the chain to be healthy;
- Proof of Work: done by randomly chosen miners;
- Secure: PBKDF authentication, with the use of salts;
- Fast checking of chain integrity
Is Packaged with a custom CLI:
Blocks stored in the database contain the following nodes:
Made from scratch, implements the hash function, given a given the steps of the algorithm.
The logo, logged in user and options need to be redefined at every command.
Getters and setters were implemented. An example is the change in options when a user is authenticated (options like "send pisiticoins" are added) versus not authenticated ( options like "log in" are added).
Using pynput, creates a listener for keys such as arrows and enter. Although other, easier to implement, libraries exist, this was the only one that provided a solution supported in Windows and Linux. Compatibility is one of the goals of this project.
Re-renders the screen as soon as one of those is pressed.
The module OptionsMenu.py is a collection of functions wich need to communicate with each other.
As I didn't want to define them with many arguments each, the first idea was to create global variables. This, however, is ill-advised in basically all the forums I researched.
The solution I came up with, then, was to use Environment variables. It works nicely, even though I it is not its intended use. One negative aspect is that they only accept strings. Therefore, the use of "true" and "false" were required.
In hindsight, a more elegant solution would be to simply wrap all of the function with a class. The required variables would, then, be accessible by every method. To kickstart the menu, the addition of a start() or begin() method that calls the others would suffice.
Two classes with multiple methods used to perform the various queries to the database required for the main program.
All of the communication with the sqlite db is done via these functions.
Therefore, the end user does not need to understand the underlying schema or implement custom queries.
They are devided into getters, setters and updaters.
An account id is derived using PBKDF2 with 10,000 rounds and 16 bytes long salts. Only such id is stored in the database.
Logging in repeats the process for every salt stored and matches its corresponding id.
Database is pre-populated accounts, whose passphrases are each one of the lower case letters from "a" to "m".
Rehashes every block, in order, to determine inconsistencies.
Breaks chain integrity until fixing or remining of all blocks is executed.
Remines necessary blocks.
Remines every block and tries to figure out a non destructive way of fixing the chain.
Prompts the user for an account, then print its balance.
Requires user to be logged in and have a sufficiently large balance.
Pretty prints a blocks's information.
Recalculates every user's balance by going through every block, in order.
Recomended using a virtual environment.
Install dependencies
pip install -r requirements.txtRun
python3 src/PisitiCoin.py. Create a new account or log in to one of the existing ones whose passphrases are each one of the lower case letters from "a" to "m".
Comes with pre populated blockchain. Give it a try!