Minimint

This is an experimental implementation of a federated Chaumian bank. DO NOT USE IT WITH REAL MONEY, THERE ARE MULTIPLE KNOWN SECURITY ISSUES.

Running MiniMint locally

MiniMint is tested and developed using rust stable, you can get it through your package manager or from rustup.rs.

Generating config

You first need to generate some config. All scripts assume config to be located in a folder called cfg. Then you can generate the necessary configuration files as follows:

mkdir -p cfg
cargo run --bin configgen cfg <num_nodes> 5000 6000 <tier1> <tier2> …

<num_nodes> is the amount of nodes the federation shall consist of. It should be >=4 (I always test with 5) and not too big as the cryptography of the BFT protocol is rather intense and you should ideally have 1 core per node. The numbers 5000 and 6000 specify the beginning of the port range the inner-federation sockets and API sockets bind to. The remaining arguments will be interpreted as amount tiers in msat.

This will both create all the server-n.json config files and one client.json. If you want to play with multiple clients you should create one subdirectory per client and copy the client.json into each.

Running the mints

A script for running all mints and a regtest bitcoind at once is provided at scripts/startfed.sh. Run it as follows:

bash scripts/startfed.sh <num_nodes> 0

The 0 in the end specifies how many nodes to leave out. E.g. changing it to one would skip the first node. This is useful to run a single node with a debugger attached.

Log output can be adjusted using the RUST_LOG environment variable and is set to info by default. Logging can be adjusted per module, see the env_logger documentation for details.

Using the client

First you need to make sure that your regtest bitcoind has some coins that are mature. For that you can generate a few hundred blocks to your own wallet:

ADDRESS="$(bitcoin-cli -regtest -rpcuser=bitcoin -rpcpassword=bitcoin getnewaddress)"
bitcoin-cli -regtest -rpcuser=bitcoin -rpcpassword=bitcoin generatetoaddress 200 "$ADDRESS"

Then you can use the peg-in script to deposit funds. It contains comments that explain the deposit process.

bash scripts/pegin.sh <amount in BTC>

Take care to not request too big of a peg-in (depending on your amount tier the smallest representations as tokens might be too big to finish signing in reasonable time) or too small (there is a 500sat fee that needs to be paid). After about 20s your default client in cfg should have newly issued coins.

You can view your client's holdings using the info command:

minimint $ cargo run --bin mint-client --release -- cfg info
    Finished release [optimized] target(s) in 0.11s
     Running `target/release/mint-client cfg info`
Jun 15 14:57:22.066  INFO mint_client: We own 14 coins with a total value of 9500000 msat
Jun 15 14:57:22.066  INFO mint_client: We own 5 coins of denomination 100000 msat
Jun 15 14:57:22.066  INFO mint_client: We own 9 coins of denomination 1000000 msat

The spend subcommand allows to send tokens to another client. This will select the smallest possible set of the client's coins that represents a given amount. The coins are base64 encoded and printed to stdout.

minimint $ cargo run --bin mint-client --release -- cfg spend 400000
    Finished release [optimized] target(s) in 0.12s
     Running `target/release/mint-client cfg spend 400000`
AQAAAAAAAACghgEAAAAAAAQAAAAAAAAAA7mGus9L4ojsIsctFK7oNz5s4ozZe3pVa0S1jZ3XvSnMMAAAAAAAAACFjOG3a4vlxBOCa9fYD6qWIM2JhH9vitG0
DXQhd9KhGYKheKADLOVXgZwOQDX0NheGP5fFEMYOfidY1FPXB1qRhrEiZKh3YVb2i922uUHoggOsZhrLpk4EGCJjuT1QUWpO8HZ9WOxD4oUv6nPNVQnKvDAA
AAAAAAAAoXKhtm/0w8pFz7CN6xcEQUnukrNcfhc/NtRita1vvZDyX/NBiSmHZVyWx8WEloclIw0A8ljJhp+b517c1LsLJ5Z6Issf9QcV/hwAgY/RJo4DRGWD
IDyyyBYXxRbFuTZoDaTR3TM/49m41Bl7/CPVz98wAAAAAAAAAJOjsZSwWrBUXt+OsojEkxRbqn8KAJrz1TTQkNrdlEiaSRqjx+YCfET3HwL3j26s2clhRugM
rRj6oMC6wKoZz0jCuS5i8faLRHGZp3AMR1/xAvMglQZ9zMEDdDd7dcxwp9WpR6JfdAUJku3EGQ/FUXaQMAAAAAAAAACUXn9s935ruZ5jA5o5aNf1u/smH4TN
+qO8jMHVf6Zzh22P5jJvhWdX62s7kftXTa9AKeiC0I4QxWdWVK4JTLnE62GzGLQqQyEkne3Pn/Pm1g==

A receiving client can now reissue these coins to claim them and avoid double spends:

minimint $ cargo run --bin mint-client --release -- cfg reissue AQAAAAAAAACghgE…
    Finished release [optimized] target(s) in 0.13s
     Running `target/release/mint-client cfg reissue AQAAAAAAAACghgE…
Jun 15 15:01:47.027  INFO mint_client: Starting reissuance transaction for 400000 msat
Jun 15 15:01:47.040  INFO mint_client: Started reissuance 47d8f08710423c1e300854ecb6463ca6185e4b3890bbbb90fd1ff70c72e1ed18, please fetch the result later
minimint $ cargo run --bin mint-client --release -- cfg fetch
    Finished release [optimized] target(s) in 0.12s
     Running `target/release/mint-client cfg fetch`
Jun 15 15:02:06.264  INFO mint_client: Fetched coins from issuance 47d8f08710423c1e300854ecb6463ca6185e4b3890bbbb90fd1ff70c72e1ed18

There also exist some other, more experimental commands that can be explored using the --help flag:

minimint $ cargo run --bin mint-client --release -- --help
    Finished release [optimized] target(s) in 0.12s
     Running `target/release/mint-client --help`
mint-client 0.1.0

USAGE:
    mint-client <workdir> <SUBCOMMAND>

FLAGS:
    -h, --help       Prints help information
    -V, --version    Prints version information

ARGS:
    <workdir>    

SUBCOMMANDS:
    fetch             Fetch (re-)issued coins and finalize issuance process
    help              Prints this message or the help of the given subcommand(s)
    info              Display wallet info (holdings, tiers)
    ln-pay            Pay a lightning invoice via a gateway
    peg-in            Issue tokens in exchange for a peg-in proof (not yet implemented, just creates coins)
    peg-in-address    Generate a new peg-in address, funds sent to it can later be claimed
    peg-out           Withdraw funds from the federation
    reissue           Reissue tokens received from a third party to avoid double spends
    spend             Prepare coins to send to a third party as a payment