WOA - Witness of Authority - Vapory Bridge

Software, written in Rust, used by WOA bridge validators to faciliate proof-of-authority based bridging of WOA native coins to tokens on another Vapory-based blockchain. The validators work with the WOA bridge contracts to convert ether on one chain into the same amount of VRC20 tokens on the other and back. This software was designed to work in conjunction with the following projects. Current compatability is unknown. * WOA Bridge UI * WOA Bridge Smart Contracts * WOA Bridge Monitoring service * WOA Bridge Deployment scripts

Functionality

The bridge connects two chains (home and foreign). When a user deposits ether into the bridge contract contract on home they get the same amount of VRC20 tokens on foreign, and they can convert them back as well.

Deposit

Withdraw

Difference from Parity Bridge

Although the WOA bridge was initially based on the Parity Bridge, it was re-worked to include: * support of a gas price oracle introduced; * RPC is used instead of IPC; * sending of bridge approvals enhanced, increasing performance dramatically; * error handling improved to be compatible with Linux systemd facility; * bridge configuration parameters are fetched from bridge contracts so they don't need to be synchronized among several bridge instances; * bridge contracts were segregated into the separate project and their deployment is independent from the Rust side of the bridge. Now bridge contracts: * are separate from VRC20 * are upgradable; you don't need to re-configure bridge instances and DApps to use new version of contracts * allow a set of validators to be changed without neeeding to re-deploy thebridge contracts

How to build

Requires rust and cargo: installation instructions. Requires solc to be in $PATH: installation instructions. Assuming you've cloned the bridge (git clone git@github.com:poanetwork/poa-bridge.git), run cd woa-bridge make and install ../target/release/bridge in your $PATH.

Running

bridge --config config.toml --database db.toml - --config - location of the configuration file. configuration file must exist - --database - location of the database file. Bridge forces TLS for RPC connections by default. However, in some limited scenarios (like local testing), this might be undesirable. In this case, you can use the --allow-insecure-rpc-endpoints option to allow non-TLS endpoints to be used. Ensure, however, that this option is not going to be used in production.

Exit Status Codes

| Code | Meaning | ------|----------------------| 0 | Success | 1 | Unknwon error | 2 | I/O error | 3 | Shutdown requested | 4 | Insufficient funds | 5 | Gas too low | 6 | Gas price is too | low | 7 | Nonce reused | | 10 | Cannot connect | 11 | Connection lost | 12 | Bridge crashed | 20 | RPC error |

Configuration file example

required_confirmations = 0 poll_interval = 5 request_timeout = 60 default_gas_price = 1_000_000_000 # 1 GWEI [foreign] account = "0x006e27b6a72e1f34c626762f3c4761547aff1421" password = 
"foreign_password.txt" rpc_host = "http://localhost" rpc_port = 9545 required_confirmations = 8 poll_interval = 15 request_timeout = 60 gas_price_oracle_url = "https://gasprice.poa.network" 
gas_price_speed = "instant" gas_price_timeout = 10 default_gas_price = 10_000_000_000 # 10 GWEI [authorities] [transactions] deposit_relay = { gas = 300000 } withdraw_relay = { gas = 300000 
}
withdraw_confirm = { gas = 300000 } ```
#### Options
- `keystore` - path to a keystore directory with JSON keys
#### home/foreign options
- `home/foreign.account` - authority address on the home (**required**) - `home/foreign.password` - path to the file containing a password for the validator's account (to decrypt the key 
from the keystore) - `home/foreign.rpc_host` - RPC host (**required**) - `home/foreign.rpc_port` - RPC port (**defaults to 8545**) - `home/foreign.required_confirmations` - number of 
confirmations required to consider transaction final on home (default: **12**) - `home/foreign.poll_interval` - specify how often home node should be polled for changes (in seconds, 
default: **1**) - `home/foreign.request_timeout` - specify request timeout (in seconds, default: **3600**) - `home/foreign.gas_price_oracle_url` - the URL used to query the current 
gas-price for the home and foreign nodes, this service is known as the gas-price Oracle. This config option defaults to `None` if not supplied in the User's config TOML file. If this config 
value is `None`, no Oracle gas-price querying will occur, resulting in the config value for `home/foreign.default_gas_price` being used for all gas-prices. - 
`home/foreign.gas_price_timeout` - the number of seconds to wait for an HTTP response from the gas price oracle before using the default gas price. Defaults to `10 seconds`. - 
`home/foreign.gas_price_speed` - retrieve the gas-price corresponding to this speed when querying from an Oracle. Defaults to `fast`. The available values are: "instant", "fast", 
"standard", and "slow". - `home/foreign.default_gas_price` - the default gas price (in WEI) used in transactions with the home or foreign nodes. The `default_gas_price` is used when the 
Oracle cannot be reached. The default value is `15_000_000_000` WEI (ie. 15 GWEI). - `home/foreign.concurrent_http_requests` - the number of concurrent HTTP requests allowed in-flight 
(default: **64**)
#### transaction options
- `transaction.deposit_relay.gas` - specify how much gas should be consumed by deposit relay - `transaction.withdraw_confirm.gas` - specify how much gas should be consumed by withdraw 
confirm - `transaction.withdraw_relay.gas` - specify how much gas should be consumed by withdraw relay
### Database file format
```toml home_contract_address = "0x49edf201c1e139282643d5e7c6fb0c7219ad1db7" foreign_contract_address = "0x49edf201c1e139282643d5e7c6fb0c7219ad1db8" checked_deposit_relay = 120 
checked_withdraw_relay = 121 checked_withdraw_confirm = 121 ``` **all fields are required** - `home_contract_address` - address of the bridge contract on home chain - 
`foreign_contract_address` - address of the bridge contract on foreign chain - `checked_deposit_relay` - number of the last block for which an authority has relayed deposits to the foreign 
- `checked_withdraw_relay` - number of the last block for which an authority has relayed withdraws to the home - `checked_withdraw_confirm` - number of the last block for which an authority 
has confirmed withdraw