eth-to-bnc-bridge/README.md

## Ethereum to Binance Chain bridge

https://forum.poa.network/t/ethereum-to-binance-chain-bridge/2696

The bridge is able to transfer an ERC20 tokens on an EVM based chain to BEP2 to the Binance Chain.

It includes the following components:
1. The bridge contract on an EVM-based chain that is responsible to receive and release ERC20 tokens 
2. The orchestration contract on an EVM-based chain that participate in MPC (multy-party computations) to generate a threshold signature.
3. The oracle that monitors the chains and the send transactions. One oracle represents one bridge validator (one private key).

The idea of the bridge is similar to [the token bridge](https://github.com/poanetwork/tokenbridge) produced by [POA.Network](https://poa.network/):
- every oracle sends its confirmation as soon as a user sends the token relay request in one chain.
- when enough confirmations collected the requested amount of tokens is unlocked in another chain.

Collecting confirmations for the Binance Chain is made in form of mutlisig wallet - the validator's confirmation is participation in the transaction signature gneration with usage of Threshold Signature Scheme implemented for ECDSA by [KZen Research team](https://github.com/KZen-networks/multi-party-ecdsa).

#### Demo

This demo, at the beginning, consists of three validator parties, while only  two are enough to sign any transaction in the Binance Chain, confirm token transfer on the Ethereum Side, or vote for state changes.

An ERC20 Token is being deployed automatically on the Ethereum side of the bridge. All minted tokens are initially owned by the address associated with `DEPLOY_PRIVATE_KEY`.

BEP2 Token is used on the Binance Chain side.

All parts of this demo are docker containers.

#### Running demo:

1. Preparation
    * (1.1) Download `tbnbcli` from https://github.com/binance-chain/node-binary/tree/master/cli.
    * (1.2) Create a new account through the [web-interface](https://testnet.binance.org/en/create). Copy the private key and mnemonic phrase. The private key will be used to import it in an Ethereum Wallet. The mnemonic phrase is to recover the BNB with `tbnbcli`.
    * (1.3) Recover the account in the console with the mnemonic.
      ```
      ./tbnbcli keys add test_account1 --recover
      ```
    * (1.4) Create few BNB accounts from the console. They will be donors to provide enough funds to issue a BEP2 tokens (500 BNB required).
      ```
      ./tbnbcli keys add test_account2
      ./tbnbcli keys add test_account3
      ```
    * (1.5) Register on the Binance site and fund the accounts from the [testnet faucet](https://www.binance.com/en/dex/testnet/address).
    * (1.6) Re-arrange funds on the accounts as so the first account will have 550 BNB and others 10-20 BNBs to make transactions.
      ```
      ./tbnbcli send --from test_account2 --to <address of the first account> --amount 18500000000:BNB --chain-id=Binance-Chain-Nile --node=data-seed-pre-2-s1.binance.org:80 --memo "Test transfer"
      ./tbnbcli send --from test_account3 --to <address of the first account> --amount 18500000000:BNB --chain-id=Binance-Chain-Nile --node=data-seed-pre-2-s1.binance.org:80 --memo "Test transfer"
      ```
    * (1.7) Issue the BEP2 token from the first account
      ```
      ./tbnbcli token issue --token-name "ERC20toBEP2Bridge" --total-supply 3141500000000000 --symbol ETB0819 --from test1 --chain-id=Binance-Chain-Nile --node=data-seed-pre-2-s1.binance.org:80 --trust-node
      ```
    * (1.8) Get the BEP2 token ID in `denom` field.
      ```
      ./tbnbcli account tbnb1ack8qtpd5mm5wrjw0ajg8zpdnplw4qzeg5uuza --chain-id=Binance-Chain-Nile --node=data-seed-pre-2-s1.binance.org:80 --trust-node
      ```
    * (1.9) Clone the repo and initialize git submodules:
      ```
      git clone --recurse-submodules https://github.com/k1rill-fedoseev/eth-to-bnc-bridge.git
      ```
    * (1.10) Build TSS to be used in the bridge oracles:
      ```
      docker build -t tss -f ./src/tss/Dockerfile-local ./src/tss
      ```
2. Run test environment. (home and side ganache-cli blockchains, contracts deployment)
```./demo/start-environment.sh```
3. Run three validators in separate terminal sessions.\
```N=1 ./demo/validator-demo.sh```\
```N=2 ./demo/validator-demo.sh```\
```N=3 ./demo/validator-demo.sh```

#### Interacting with validators, sending votes, retrieving bridge information
* For each validator, a specific port is mapped outside of the docker 
container for listening GET requests
    - 5001 - first validator
    - 5002 - second validator
    - 5003 - third validator
* Retrieving bridge state
    - http://localhost:5001/info
* Voting for bridge state changes
    - http://localhost:5001/vote/startKeygen
        - After enough votes are collected, keygen process starts, and 
        ends with the transfer of all remained funds in the Binance Chain 
        to the new generated bridge account.
    - http://localhost:5001/vote/addValidator/ADDRESS
        - ```ADDRESS``` - Ethereum address of a validator.
        - After enough votes are collected, validator is added into 
        the next validators list for the next epoch.
    - http://localhost:5001/vote/addValidator/ADDRESS
        - ```ADDRESS``` - Ethereum address of a validator.
        - After enough votes are collected, validator is removed from
        the next validators list for the next epoch.
        
#### Testing tools for both sides of the bridge

In this tools, ```run.sh``` file simply builds and runs a docker container
for interacting with test blockchains. 

* ```./src/test-services/binanceSend/run.sh TO TOKENS NATIVE```
    - Sends specified amount of tokens and BNBs to the bridge account.
    - ```TO``` - receiver address in the Binance Chain.
    - ```TOKENS``` - amount of tokens to send.
    - ```NATIVE``` - amount of BNB tokens to send, if present, the 
    transaction is considered as a funding one.
* ```./src/test-services/ethereumSend/run.sh TOKENS```
    - Transfers specified amount of tokens to the bridge account.
    - ```VALUE``` - amount of tokens to transfer and exchange.
* ```./src/test-services/binanceBalance/run.sh ADDRESS```
    - Gets current BEP2 token and BNB balances of the specified account.
    - ```ADDRESS``` - account address in the Binance Chain.
* ```./src/test-services/ethereumBalance/run.sh ADDRESS```
    - Gets current ERC20 token balance of the specified account.
    - ```ADDRESS``` - Ethereum address of the account.