info_tfgrid/collections/projectinca/specs_blockchain/bridging_contract.md

# Bridging Contract

Is code which has the capability to bridge between multiple blockchains.

A bridging mechanism allows tokens to be transferred between different blockchains. Here's how it typically works:

1. A user sends tokens to the `src_bridge_address` on the source chain.
2. The bridging contract detects this transaction.
3. The lockers on the source chain verify and lock the tokens at the `src_lock_address`.
4. The minters on the destination chain are notified and create an equivalent amount of tokens on the destination chain.
5. The new tokens are released to the user's address on the destination chain.
6. The original tokens remain locked on the source chain until a reverse bridge operation is performed.

Here's an example JSON for a Bridging Contract:

```json
{
  "bridging_contract": {
    "name": "INCA_SOLANA_BNC_BRIDGE",
    "description": "Bridging contract for INCA tokens between Solana and Binance Chain",
    "address": "0x1234567890123456789012345678901234567890",
    "src_token_name": "INCA",
    "src_chain": "SOLANA",
    "src_bridge_address": "0xABCDEF1234567890ABCDEF1234567890ABCDEF12",
    "src_lock_address": "0x9876543210987654321098765432109876543210",
    "dest_token_name": "INCA",
    "dest_chain": "BNC",
    "lockers": {
      "lockers_multisig_accounts": [
        "0x1111111111111111111111111111111111111111",
        "0x2222222222222222222222222222222222222222",
        "0x3333333333333333333333333333333333333333",
        "0x4444444444444444444444444444444444444444",
        "0x5555555555555555555555555555555555555555",
        "0x6666666666666666666666666666666666666666",
        "0x7777777777777777777777777777777777777777",
        "0x8888888888888888888888888888888888888888",
        "0x9999999999999999999999999999999999999999"
      ],
      "lockers_multisig_min_signature": 6
    },
    "minters": {
      "minter_multisig_accounts": [
        "bnb1aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
        "bnb1bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
        "bnb1cccccccccccccccccccccccccccccccccccc",
        "bnb1dddddddddddddddddddddddddddddddddddd",
        "bnb1eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee",
        "bnb1ffffffffffffffffffffffffffffffffffff",
        "bnb1gggggggggggggggggggggggggggggggggggg",
        "bnb1hhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhh",
        "bnb1iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii"
      ],
      "minter_multisig_min_signature": 6
    },
    "smart_contract_addr": "0xFEDCBA9876543210FEDCBA9876543210FEDCBA98"
  }
}
```

This JSON structure represents a bridging contract for INCA tokens between Solana and Binance Chain. It includes:

1. Basic information about the bridge (name, description, address).
2. Source and destination chain details, including token names and relevant addresses.
3. Multisig requirements for lockers on the source chain.
4. Multisig requirements for minters on the destination chain.
5. The smart contract address that implements the bridging logic.

This structure allows for a secure and decentralized bridging process, requiring multiple signatures for locking tokens on the source chain, minting on the destination chain, and overall bridge operations.

### details about properties

- name 
- description
- address, the address of this contract
- src_token_name e.g. INCA in case of ThreeFold
- src_chain e.g. SOLANA
- src_bridge_address
    - address where tokens have been sent to which need to be bridged, they are locked untill executed
- src_lock_address
    - once the tokens where created on the dest chain then on source they are locked
- dest_token_name e.g. INCA in case of ThreeFold
- dest_chain e.g. BNC
- the lockers on source 
    - lockers_multisig_accounts = list e.g 9 accounts
    - lockers_multisig_min_signature: 6
- the minters on dest 
    - minter_multisig_accounts = list e.g 9 accounts
    - minter_multisig_min_signature: 6
- multisig_accounts e.g. 9 accounts need to sign
- multisig_min_signature e.g. 6 need to sign, this is for releasing the generated token INCA
- smart_contract_addr: address of the smart contract


```mermaid
sequenceDiagram
    participant User
    participant SourceChain
    participant BridgingContract
    participant DestChain

    User->>SourceChain: Send tokens to src_bridge_address
    SourceChain->>BridgingContract: Notify of received tokens
    BridgingContract->>SourceChain: Verify transaction
    
    alt Transaction valid
        BridgingContract->>SourceChain: Request token lock
        SourceChain->>SourceChain: Lock tokens at src_lock_address
        SourceChain-->>BridgingContract: Confirm lock
        
        BridgingContract->>BridgingContract: Initiate multisig process
        loop Until minimum signatures reached
            BridgingContract->>BridgingContract: Collect locker signatures
        end
        
        BridgingContract->>DestChain: Request token minting
        DestChain->>DestChain: Initiate minter multisig process
        loop Until minimum signatures reached
            DestChain->>DestChain: Collect minter signatures
        end
        
        DestChain->>DestChain: Mint equivalent tokens
        DestChain->>User: Transfer minted tokens
        DestChain-->>BridgingContract: Confirm minting and transfer
        
        BridgingContract->>User: Notify successful bridge
    else Transaction invalid
        BridgingContract->>User: Notify failed bridge
    end
```