crossChain-Bridge

crossChain-Bridge

cross chain bridge using DCRM technology

Building

git clone https://github.com/fsn-dev/crossChain-Bridge.git
cd crossChain-Bridge
make all

after building, the following files will be generated in ./build/bin directory:

swapserver	# server provide api service, and trigger swap processing
swaporacle      # oracle take part in dcrm signing (can disagree illegal transaction)
config.toml

Modify config.toml

modify the example config.toml in ./build/bin directory

see more, please refer config file example

Identifier

Identifier should be a short string to identify the bridge (eg. BTC2ETH, BTC2FSN)

MongoDB

MongoDB is used by the server to store swap status and history, you should config according to your modgodb database setting. (the swap oracle don't need it)

APIServer

APIServer is used by the server to provide API service to register swap and to provide history retrieving. (the swap oracle don't need it)

Oracle

Oracle is needed by the swap oracle to post swap register RPC requests to swap server (the swap server don't need Oracle).

BtcExtra

BtcExtra is used to customize fees when build transaction on Bitcoin blockchain

SrcToken

SrcToken is used to config the source endpoint of the cross chain bridge.

SrcGateway

SrcGateway is used to do RPC request to verify transactions on source blockchain, and to broadcast signed transaction.

DestToken

DestToken is used to config the dest endpoint of the cross chain bridge.

DestGateway

DestGateway is used to do RPC request to verify transactions on dest blockchain, and to broadcast signed transaction.

Dcrm

Dcrm is used to config DCRM node info and group info.

ServerAccount is used to specify the server dcrm user (initiator of dcrm sign)

for the swap server, Pubkey and SignGroups is needed for dcrm signing.

Notice: If in test enviroment you may run more than one program of swap servers on one machine, Please specify different log file name to clarify the outputs. And please specify different config files for each server, and assgin KeystoreFile, PasswordFile and RPCAddress etc. separatly.

Run swap server

setsid ./build/bin/swapserver --verbosity 6 --config build/bin/config.toml --log build/bin/logs/server.log

Run swap oracle

setsid ./build/bin/swaporacle --verbosity 6 --config build/bin/config.toml --log build/bin/logs/oracle.log

Others

swapserver and swaporacle has the following subcommands:

help       - to see hep info.
version - to show the version.
license - to show the license

Preparations

Running swapserver and swaporacle to provide cross chain bridge service, we must prepare the following things firstly and config them rightly. Otherwise the program will not run or run rightly. To ensure this, we have add many checkings to the config items.

For the config file, please refer config file example

1. create Mongodb database (shared by all swap servers of the bridge provider)

   config [MongoDB] section accordingly (eg. DbURL,DbName,UserName,Password)

   For security reason, we suggest:

   1. change the mongod port ( deafults to 27017)
   2. enable auth
   3. create user with passord to access the database

2. create DCRM group

   For example, we take creating 2/3 theshold jonitly managed DCRM group as an example.

   we have 3 users in the DCRM group, each user is running a gdcrm node to perform DCRM functions.

   1. user1 - build raw tx and trigger DCRM signing
   2. user2, user3 - verify tx and accept the DCRM signing with AGREE/DISAGREE result

   After created DCRM group,

   We can get the corresponding DCRM addresses on supported blockchains. Then we should config DcrmAddress in [SrcToken] and [DestToken] section according to the blockchain of them.

   We should config the [Dcrm] section accordingly（ eg. ServerAccount, GroupID, Pubkey，NeededOracles， TotalOracles，Mode）

   And we should config the following [Dcrm] section items sparately for each user in the DCRM group:

   1. KeystoreFile
   2. PasswordFile
   3. RPCAddress

   For example,

   we are configing user1 now, we should config KeystoreFile and PasswordFile use user1's keystore and password file (we will get user1's private key to sign a DCRM requesting).

   And we should config RPCAddress to the RPC address of the running gdcrm node of user1 (we will do RPC calls to this address to complete DCRM signing or accepting, etc.)

3. create DCRM sub-groups for signing

   In the above step we have created a 2/3 threshold DCRM group.

   In signing we only need 2 members to agree.

   So we prepared the sub-groups (2/2) for signing. (eg. user1 + user2, user1 + user3) please see more detail about DCRM here

   After created, we should config SignGroups in [Dcrm] accordingly.

4. create mapping asset (eg. mBTC) contract with DCRM account

   mBTC is an smart contract inherit from ERC20 and add two methods: Swapin and Swapout.

   please see more here about mBTC

   After created mBTC, we should config ContractAddress in [DestToken] section.

5. config [APIServer] section

   The swap server provides RPC service to query swap status and swap history. etc.

   Please see more here about crossChain-Bridge-API

   We should config Port (defaults to 11556), and AllowedOrigins (CORS defaults to empty array. ["*"] for allow any)

6. config [SrcToken],[SrcGateway]

   We should config APIAddress in [SrcGateway] section, to post RPC request to the running full node to get transaction, broadcat transaction etc.

   Config [SrcToken], ref. to the following example:

   BlockChain = "Bitcoin" # required
   NetID = "TestNet3"  # required
   ID = ""
   Name = "Bitcoin Coin"
   Symbol = "BTC"
   Decimals = 8  # required
   Description = "Bitcoin Coin"
   ContractAddress = ""
   DcrmAddress = "mfwPnCuht2b4Lvb5XTds4Rvzy3jZ2ZWrBL" # required
   Confirmations = 0 # suggest >= 6 for Mainnet # required
   MaximumSwap = 1000.0 # required
   MinimumSwap = 0.00001 # required
   SwapFeeRate = 0.001 # required
   

   For ERC20 token, we should config ID = "ERC20" and ContractAddress to the token's contract address.

7. config [DestToken], [DestGateway]

   We should config APIAddress in [DestGateway] section, to post RPC request to the running full node to get transaction, broadcat transaction etc.

   Config [DestToken] like [SrcToken].

   Don't forget to config ContractAddress in [DestToken] section (see step 4)

8. config Identifier to identify your crosschain bridge

   This should be a short string to identify the bridge (eg. BTC2ETH, BTC2FSN)

   Different DCRM group can have same Identifier.

   It only matter if you want use a DCRM group to provide multiple crosschain bridge service, and config each bridge with a different identifier (Notice: This way is not suggested)

9. config [BtcExtra]

   When build and sign transaction on Bitcoin blockchain, we can customize the following items:

   MinRelayFee   = 400
   RelayFeePerKb = 2000
   UtxoAggregateMinCount = 20
   UtxoAggregateMinValue = 1000000
   

   If not configed, the default vlaue will be used (in fact, the above values are the defaults)