Go Language dns seeder for Bitcoin based networks
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blockchain
==========
[![Build Status](http://img.shields.io/travis/btcsuite/btcd.svg)]
(https://travis-ci.org/btcsuite/btcd) [![ISC License]
(http://img.shields.io/badge/license-ISC-blue.svg)](http://copyfree.org)
Package blockchain implements bitcoin block handling and chain selection rules.
The test coverage is currently only around 60%, but will be increasing over
time. See `test_coverage.txt` for the gocov coverage report. Alternatively, if
you are running a POSIX OS, you can run the `cov_report.sh` script for a
real-time report. Package blockchain is licensed under the liberal ISC license.
There is an associated blog post about the release of this package
[here](https://blog.conformal.com/btcchain-the-bitcoin-chain-package-from-bctd/).
This package has intentionally been designed so it can be used as a standalone
package for any projects needing to handle processing of blocks into the bitcoin
block chain.
## Documentation
[![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg)]
(http://godoc.org/github.com/btcsuite/btcd/blockchain)
Full `go doc` style documentation for the project can be viewed online without
installing this package by using the GoDoc site here:
http://godoc.org/github.com/btcsuite/btcd/blockchain
You can also view the documentation locally once the package is installed with
the `godoc` tool by running `godoc -http=":6060"` and pointing your browser to
http://localhost:6060/pkg/github.com/btcsuite/btcd/blockchain
## Installation
```bash
$ go get github.com/btcsuite/btcd/blockchain
```
## Bitcoin Chain Processing Overview
Before a block is allowed into the block chain, it must go through an intensive
series of validation rules. The following list serves as a general outline of
those rules to provide some intuition into what is going on under the hood, but
is by no means exhaustive:
- Reject duplicate blocks
- Perform a series of sanity checks on the block and its transactions such as
verifying proof of work, timestamps, number and character of transactions,
transaction amounts, script complexity, and merkle root calculations
- Compare the block against predetermined checkpoints for expected timestamps
and difficulty based on elapsed time since the checkpoint
- Save the most recent orphan blocks for a limited time in case their parent
blocks become available
- Stop processing if the block is an orphan as the rest of the processing
depends on the block's position within the block chain
- Perform a series of more thorough checks that depend on the block's position
within the block chain such as verifying block difficulties adhere to
difficulty retarget rules, timestamps are after the median of the last
several blocks, all transactions are finalized, checkpoint blocks match, and
block versions are in line with the previous blocks
- Determine how the block fits into the chain and perform different actions
accordingly in order to ensure any side chains which have higher difficulty
than the main chain become the new main chain
- When a block is being connected to the main chain (either through
reorganization of a side chain to the main chain or just extending the
main chain), perform further checks on the block's transactions such as
verifying transaction duplicates, script complexity for the combination of
connected scripts, coinbase maturity, double spends, and connected
transaction values
- Run the transaction scripts to verify the spender is allowed to spend the
coins
- Insert the block into the block database
## Examples
* [ProcessBlock Example]
(http://godoc.org/github.com/btcsuite/btcd/blockchain#example-BlockChain-ProcessBlock)
Demonstrates how to create a new chain instance and use ProcessBlock to
attempt to attempt add a block to the chain. This example intentionally
attempts to insert a duplicate genesis block to illustrate how an invalid
block is handled.
* [CompactToBig Example]
(http://godoc.org/github.com/btcsuite/btcd/blockchain#example-CompactToBig)
Demonstrates how to convert the compact "bits" in a block header which
represent the target difficulty to a big integer and display it using the
typical hex notation.
* [BigToCompact Example]
(http://godoc.org/github.com/btcsuite/btcd/blockchain#example-BigToCompact)
Demonstrates how to convert how to convert a target difficulty into the
compact "bits" in a block header which represent that target difficulty.
## GPG Verification Key
All official release tags are signed by Conformal so users can ensure the code
has not been tampered with and is coming from the btcsuite developers. To
verify the signature perform the following:
- Download the public key from the Conformal website at
https://opensource.conformal.com/GIT-GPG-KEY-conformal.txt
- Import the public key into your GPG keyring:
```bash
gpg --import GIT-GPG-KEY-conformal.txt
```
- Verify the release tag with the following command where `TAG_NAME` is a
placeholder for the specific tag:
```bash
git tag -v TAG_NAME
```
## License
Package blockchain is licensed under the [copyfree](http://copyfree.org) ISC
License.