BNB Smart Chain

The goal of BNB Smart Chain is to bring programmability and interoperability to BNB Beacon Chain. In order to embrace the existing popular community and advanced technology, it will bring huge benefits by staying compatible with all the existing smart contracts on Ethereum and Ethereum tooling. And to achieve that, the easiest solution is to develop based on go-ethereum fork, as we respect the great work of Ethereum very much.

BNB Smart Chain starts its development based on go-ethereum fork. So you may see many toolings, binaries and also docs are based on Ethereum ones, such as the name “geth”.

But from that baseline of EVM compatible, BNB Smart Chain introduces a system of 21 validators with Proof of Staked Authority (PoSA) consensus that can support short block time and lower fees. The most bonded validator candidates of staking will become validators and produce blocks. The double-sign detection and other slashing logic guarantee security, stability, and chain finality.

Cross-chain transfer and other communication are possible due to native support of interoperability. Relayers and on-chain contracts are developed to support that. BNB Beacon Chain DEX remains a liquid venue of the exchange of assets on both chains. This dual-chain architecture will be ideal for users to take advantage of the fast trading on one side and build their decentralized apps on the other side. The BNB Smart Chain will be:

• A self-sovereign blockchain: Provides security and safety with elected validators.
• EVM-compatible: Supports all the existing Ethereum tooling along with faster finality and cheaper transaction fees.
• Interoperable: Comes with efficient native dual chain communication; Optimized for scaling high-performance dApps that require fast and smooth user experience.
• Distributed with on-chain governance: Proof of Staked Authority brings in decentralization and community participants. As the native token, BNB will serve as both the gas of smart contract execution and tokens for staking.

More details in White Paper.

Key features

Proof of Staked Authority

Although Proof-of-Work (PoW) has been approved as a practical mechanism to implement a decentralized network, it is not friendly to the environment and also requires a large size of participants to maintain the security.

Proof-of-Authority(PoA) provides some defense to 51% attack, with improved efficiency and tolerance to certain levels of Byzantine players (malicious or hacked). Meanwhile, the PoA protocol is most criticized for being not as decentralized as PoW, as the validators, i.e. the nodes that take turns to produce blocks, have all the authorities and are prone to corruption and security attacks.

Other blockchains, such as EOS and Cosmos both, introduce different types of Deputy Proof of Stake (DPoS) to allow the token holders to vote and elect the validator set. It increases the decentralization and favors community governance.

To combine DPoS and PoA for consensus, BNB Smart Chain implement a novel consensus engine called Parlia that:

1. Blocks are produced by a limited set of validators.
2. Validators take turns to produce blocks in a PoA manner, similar to Ethereum's Clique consensus engine.
3. Validator set are elected in and out based on a staking based governance on BNB Beacon Chain.
4. The validator set change is relayed via a cross-chain communication mechanism.
5. Parlia consensus engine will interact with a set of system contracts to achieve liveness slash, revenue distributing and validator set renewing func.

Light Client of BNB Beacon Chain

To achieve the cross-chain communication from BNB Beacon Chain to BNB Smart Chain, need introduce a on-chain light client verification algorithm. It contains two parts:

1. Stateless Precompiled contracts to do tendermint header verification and Merkle Proof verification.
2. Stateful solidity contracts to store validator set and trusted appHash.

Native Token

BNB will run on BNB Smart Chain in the same way as ETH runs on Ethereum so that it remains as native token for BSC. This means, BNB will be used to:

1. pay gas to deploy or invoke Smart Contract on BSC
2. perform cross-chain operations, such as transfer token assets across BNB Smart Chain and BNB Beacon Chain.

Building the source

Many of the below are the same as or similar to go-ethereum.

For prerequisites and detailed build instructions please read the Installation Instructions.

Building geth requires both a Go (version 1.18 or later) and a C compiler. You can install them using your favourite package manager. Once the dependencies are installed, run

make geth

or, to build the full suite of utilities:

make all

Executables

The bsc project comes with several wrappers/executables found in the cmd directory.

Command	Description
geth	Main BNB Smart Chain client binary. It is the entry point into the BSC network (main-, test- or private net), capable of running as a full node (default), archive node (retaining all historical state) or a light node (retrieving data live). It has the same and more RPC and other interface as go-ethereum and can be used by other processes as a gateway into the BSC network via JSON RPC endpoints exposed on top of HTTP, WebSocket and/or IPC transports. geth --help and the CLI page for command line options.
clef	Stand-alone signing tool, which can be used as a backend signer for geth.
devp2p	Utilities to interact with nodes on the networking layer, without running a full blockchain.
abigen	Source code generator to convert Ethereum contract definitions into easy to use, compile-time type-safe Go packages. It operates on plain Ethereum contract ABIs with expanded functionality if the contract bytecode is also available. However, it also accepts Solidity source files, making development much more streamlined. Please see our Native DApps page for details.
bootnode	Stripped down version of our Ethereum client implementation that only takes part in the network node discovery protocol, but does not run any of the higher level application protocols. It can be used as a lightweight bootstrap node to aid in finding peers in private networks.
evm	Developer utility version of the EVM (Ethereum Virtual Machine) that is capable of running bytecode snippets within a configurable environment and execution mode. Its purpose is to allow isolated, fine-grained debugging of EVM opcodes (e.g. evm --code 60ff60ff --debug run).
rlpdump	Developer utility tool to convert binary RLP (Recursive Length Prefix) dumps (data encoding used by the Ethereum protocol both network as well as consensus wise) to user-friendlier hierarchical representation (e.g. rlpdump --hex CE0183FFFFFFC4C304050583616263).

Running geth

Going through all the possible command line flags is out of scope here (please consult our CLI Wiki page), but we've enumerated a few common parameter combos to get you up to speed quickly on how you can run your own geth instance.

Hardware Requirements

The hardware must meet certain requirements to run a full node on mainnet:

• VPS running recent versions of Mac OS X, Linux, or Windows.
• IMPORTANT 2 TB of free disk space, solid-state drive(SSD), gp3, 8k IOPS, 250 MB/S throughput, read latency <1ms. (if node is started with snap sync, it will need NVMe SSD)
• 16 cores of CPU and 64 GB of memory (RAM)
• Suggest m5zn.3xlarge instance type on AWS, c2-standard-16 on Google cloud.
• A broadband Internet connection with upload/download speeds of 5 MB/S

The requirement for testnet:

• VPS running recent versions of Mac OS X, Linux, or Windows.
• 500G of storage for testnet.
• 4 cores of CPU and 8 gigabytes of memory (RAM).

Steps to Run a Fullnode

1. Download the pre-build binaries

# Linux
wget $(curl -s https://api.github.com/repos/bnb-chain/bsc/releases/latest |grep browser_ |grep geth_linux |cut -d\" -f4)
mv geth_linux geth
chmod -v u+x geth

# MacOS
wget $(curl -s https://api.github.com/repos/bnb-chain/bsc/releases/latest |grep browser_ |grep geth_mac |cut -d\" -f4)
mv geth_mac geth
chmod -v u+x geth

2. Download the config files

wget $(curl -s https://api.github.com/repos/bnb-chain/bsc/releases/latest |grep browser_ |grep mainnet |cut -d\" -f4)
unzip mainnet.zip

3. Download snapshot

Download latest chaindata snapshot from here. Follow the guide to structure your files.

4. Start a full node

./geth --config ./config.toml --datadir ./node  --cache 8000 --rpc.allow-unprotected-txs --txlookuplimit 0

## It is recommand to run fullnode with `--tries-verify-mode none` if you want high performance and care little about state consistency
./geth --config ./config.toml --datadir ./node  --cache 8000 --rpc.allow-unprotected-txs --txlookuplimit 0 --tries-verify-mode none

5. Monitor node status

Monitor the log from ./node/bsc.log by default. When the node has started syncing, should be able to see the following output:

t=2022-09-08T13:00:27+0000 lvl=info msg="Imported new chain segment"             blocks=1    txs=177   mgas=17.317   elapsed=31.131ms    mgasps=556.259  number=21,153,429 hash=0x42e6b54ba7106387f0650defc62c9ace3160b427702dab7bd1c5abb83a32d8db dirty="0.00 B"
t=2022-09-08T13:00:29+0000 lvl=info msg="Imported new chain segment"             blocks=1    txs=251   mgas=39.638   elapsed=68.827ms    mgasps=575.900  number=21,153,430 hash=0xa3397b273b31b013e43487689782f20c03f47525b4cd4107c1715af45a88796e dirty="0.00 B"
t=2022-09-08T13:00:33+0000 lvl=info msg="Imported new chain segment"             blocks=1    txs=197   mgas=19.364   elapsed=34.663ms    mgasps=558.632  number=21,153,431 hash=0x0c7872b698f28cb5c36a8a3e1e315b1d31bda6109b15467a9735a12380e2ad14 dirty="0.00 B"

6. Interact with fullnode

Start up geth's built-in interactive JavaScript console, (via the trailing console subcommand) through which you can interact using web3 methods (note: the web3 version bundled within geth is very old, and not up to date with official docs), as well as geth's own management APIs. This tool is optional and if you leave it out you can always attach to an already running geth instance with geth attach.

7. More

More details about running a node and becoming a validator

Note: Although there are some internal protective measures to prevent transactions from crossing over between the main network and test network, you should make sure to always use separate accounts for play-money and real-money. Unless you manually move accounts, geth will by default correctly separate the two networks and will not make any accounts available between them.

Configuration

As an alternative to passing the numerous flags to the geth binary, you can also pass a configuration file via:

$ geth --config /path/to/your_config.toml

To get an idea how the file should look like you can use the dumpconfig subcommand to export your existing configuration:

$ geth --your-favourite-flags dumpconfig

Programmatically interfacing geth nodes

As a developer, sooner rather than later you'll want to start interacting with geth and the BSC network via your own programs and not manually through the console. To aid this, geth has built-in support for a JSON-RPC based APIs (standard APIs and geth specific APIs). These can be exposed via HTTP, WebSockets and IPC (UNIX sockets on UNIX based platforms, and named pipes on Windows).

The IPC interface is enabled by default and exposes all the APIs supported by geth, whereas the HTTP and WS interfaces need to manually be enabled and only expose a subset of APIs due to security reasons. These can be turned on/off and configured as you'd expect.

HTTP based JSON-RPC API options:

• --http Enable the HTTP-RPC server
• --http.addr HTTP-RPC server listening interface (default: localhost)
• --http.port HTTP-RPC server listening port (default: 8545)
• --http.api API's offered over the HTTP-RPC interface (default: eth,net,web3)
• --http.corsdomain Comma separated list of domains from which to accept cross origin requests (browser enforced)
• --ws Enable the WS-RPC server
• --ws.addr WS-RPC server listening interface (default: localhost)
• --ws.port WS-RPC server listening port (default: 8546)
• --ws.api API's offered over the WS-RPC interface (default: eth,net,web3)
• --ws.origins Origins from which to accept WebSocket requests
• --ipcdisable Disable the IPC-RPC server
• --ipcapi API's offered over the IPC-RPC interface (default: admin,debug,eth,miner,net,personal,txpool,web3)
• --ipcpath Filename for IPC socket/pipe within the datadir (explicit paths escape it)

You'll need to use your own programming environments' capabilities (libraries, tools, etc) to connect via HTTP, WS or IPC to a geth node configured with the above flags and you'll need to speak JSON-RPC on all transports. You can reuse the same connection for multiple requests!

Note: Please understand the security implications of opening up an HTTP/WS based transport before doing so! Hackers on the internet are actively trying to subvert BSC nodes with exposed APIs! Further, all browser tabs can access locally running web servers, so malicious web pages could try to subvert locally available APIs!

Operating a private network

• BSC-Deploy: deploy tool for setting up both BNB Beacon Chain, BNB Smart Chain and the cross chain infrastructure between them.
• BSC-Docker: deploy tool for setting up local BSC cluster in container.

Contribution

Thank you for considering to help out with the source code! We welcome contributions from anyone on the internet, and are grateful for even the smallest of fixes!

If you'd like to contribute to bsc, please fork, fix, commit and send a pull request for the maintainers to review and merge into the main code base. If you wish to submit more complex changes though, please check up with the core devs first on our discord channel to ensure those changes are in line with the general philosophy of the project and/or get some early feedback which can make both your efforts much lighter as well as our review and merge procedures quick and simple.

Please make sure your contributions adhere to our coding guidelines:

• Code must adhere to the official Go formatting guidelines (i.e. uses gofmt).
• Code must be documented adhering to the official Go commentary guidelines.
• Pull requests need to be based on and opened against the master branch.
• Commit messages should be prefixed with the package(s) they modify.
  • E.g. "eth, rpc: make trace configs optional"

Please see the Developers' Guide for more details on configuring your environment, managing project dependencies, and testing procedures.

License

The bsc library (i.e. all code outside of the cmd directory) is licensed under the GNU Lesser General Public License v3.0, also included in our repository in the COPYING.LESSER file.

The bsc binaries (i.e. all code inside of the cmd directory) is licensed under the GNU General Public License v3.0, also included in our repository in the COPYING file.