# SHA-256 Miner (From Scratch, Python Starter)

A clean, production-minded **starting point** for building SHA-256 miners from scratch.

This repository provides a complete, readable Python implementation of a Bitcoin-style mining pipeline using `getblocktemplate` and JSON-RPC. It is intentionally written in Python to keep the architecture simple, inspectable, and easy to evolve.

## Positioning

This project is designed for engineers who want to:
- understand mining internals end-to-end
- customize nonce-search and block-building logic
- use a practical base before moving performance-critical parts to lower-level languages

This project is **not** an ASIC-grade miner and is **not** intended for profitable mainnet mining.

## What You Get

- End-to-end mining flow (`template -> coinbase -> merkle -> header -> PoW -> submit`)
- Multiprocess worker orchestration
- Worker-specific `extranonce2` generation
- SegWit-aware template processing
- Coinbase construction with custom message support
- Block serialization and submission to Bitcoin Core
- Watchdog-based restart on chain tip updates
- Live aggregated dashboard (attempts/hashrate by worker)

## Repository Layout

- `launcher.py`: supervisor, process lifecycle, dashboard
- `main.py`: single-worker mining loop
- `miner.py`: PoW nonce search engine
- `block_builder.py`: coinbase/header/block assembly
- `rpc.py`: Bitcoin Core RPC client helpers
- `utils.py`: hashing, target conversion, watchdog logic
- `config.py`: runtime configuration
- `config.py.example`: full configuration template

## Architecture Overview

1. `launcher.py` starts N worker processes.
2. Each worker requests a fresh block template from Bitcoin Core.
3. Coinbase is built using block height, optional message, `EXTRANONCE1`, and worker-specific `EXTRANONCE2`.
4. Merkle root and block header are assembled.
5. `miner.py` searches for a valid nonce according to the selected strategy.
6. If a valid header is found, the block is serialized and submitted.
7. Workers restart with a new template after successful submission or tip change.

## Requirements

- Python 3.10+
- Bitcoin Core node with RPC enabled
- Recommended network for development: `regtest`

Install:

```bash
python -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
```

## Bitcoin Core Setup

Example `bitcoin.conf` values:

```ini
server=1
rpcuser=user
rpcpassword=password
rpcallowip=127.0.0.1
rpcport=18443
regtest=1
```

Use values consistent with your local node and wallet setup.

## Configuration (`config.py`)

All runtime settings are defined in `config.py`.
Use `config.py.example` as the canonical template.

Minimal example:

```python
import multiprocessing as mp

# RPC
RPC_USER = "user"
RPC_PASSWORD = "password"
RPC_HOST = "127.0.0.1"
RPC_PORT = 8332

# Wallet
WALLET_ADDRESS = ""

# Mining
DIFFICULTY_FACTOR = 1.0
NONCE_MODE = "incremental"  # incremental | random | mixed
TIMESTAMP_UPDATE_INTERVAL = 30
BATCH = 10_000
COINBASE_MESSAGE = "/py-miner/"
EXTRANONCE1 = "1234567890abcdef"
EXTRANONCE2 = "12341234"

# Workers
_NUM_PROCESSORS = 0
NUM_PROCESSORS = _NUM_PROCESSORS if _NUM_PROCESSORS > 0 else mp.cpu_count()

# Watchdog
CHECK_INTERVAL = 20
```

## Supported Configuration Behavior

- `NONCE_MODE`: must be `incremental`, `random`, or `mixed`
- `TIMESTAMP_UPDATE_INTERVAL`: seconds, `0` disables periodic timestamp updates
- `BATCH`: number of nonces per compute batch
- `NUM_PROCESSORS`:
  - `> 0`: exact number of workers
  - `<= 0`: auto CPU count
- `DIFFICULTY_FACTOR`:
  - on `regtest`:
    - `0`: keep original template target
    - `> 0`: compute target as `max_target / factor`
    - `< 0`: clamped to `0.1`
  - on non-`regtest`: forced to `1.0`

## Run

Default:

```bash
python launcher.py
```

CLI options:
- `-n`, `--num-procs`: number of workers
- `--base-extranonce2`: base hex value for per-worker extranonce2 derivation

Example:

```bash
python launcher.py -n 4 --base-extranonce2 12341234
```

## Operational Notes

- `EXTRANONCE1` and `EXTRANONCE2` must be valid hex strings.
- Coinbase `scriptSig` must remain within protocol constraints (the implementation enforces a 100-byte limit).
- Invalid RPC credentials or invalid wallet address will fail at runtime.

## Tested Capacity

Reference test result for this miner implementation:
- Platform: Raspberry Pi 5
- CPU usage: 4 cores
- Observed throughput: **~1.8 MH/s**

Performance depends on clock profile, thermal conditions, operating system, and background load.

## Current Limits (By Design)

This is a Python starter implementation. It intentionally does not include:
- ASIC/GPU kernels
- Stratum server/client stack
- advanced failover/job persistence
- extensive benchmark/profiling harness

## Recommended Evolution Path

1. Add strict schema validation for `config.py`.
2. Add deterministic unit tests for block assembly and hashing paths.
3. Introduce microbenchmarks for nonce-loop and hashing batches.
4. Add integration tests against disposable `bitcoind` `regtest` nodes.
5. Extract core components into reusable packages (RPC, builder, PoW engine).
6. Move performance-critical sections to C/Rust/CUDA while preserving Python orchestration.

## License

MIT. See [LICENSE](LICENSE).