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Hernando Castano
72 lines
3.8 KiB
Markdown
72 lines
3.8 KiB
Markdown
# PoA Ethereum High Level Documentation
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NOTE: This is from the old README
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### Ethereum Bridge Runtime Module
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The main job of this runtime module is to keep track of useful information an Ethereum PoA chain
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which has been submitted by a bridge relayer. This includes:
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- Ethereum headers and their status (e.g are they the best header, are they finalized, etc.)
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- Current validator set, and upcoming validator sets
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This runtime module has more responsibilties than simply storing headers and validator sets. It is
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able to perform checks on the incoming headers to verify their general integrity, as well as whether
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or not they've been finalized by the authorities on the PoA chain.
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This module is laid out as so:
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```
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├── ethereum
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│ └── src
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│ ├── error.rs // Runtime error handling
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│ ├── finality.rs // Manage finality operations
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│ ├── import.rs // Import new Ethereum headers
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│ ├── lib.rs // Store headers and validator set info
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│ ├── validators.rs // Track current and future PoA validator sets
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│ └── verification.rs // Verify validity of incoming Ethereum headers
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```
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### Currency Exchange Runtime Module
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The currency exchange module is used to faciliate cross-chain funds transfers. It works by accepting
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a transaction which proves that funds were locked on one chain, and releases a corresponding amount
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of funds on the recieving chain.
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For example: Alice would like to send funds from chain A to chain B. What she would do is send a
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transaction to chain A indicating that she would like to send funds to an address on chain B. This
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transaction would contain the amount of funds she would like to send, as well as the address of the
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recipient on chain B. These funds would now be locked on chain A. Once the block containing this
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"locked-funds" transaction is finalized it can be relayed to chain B. Chain B will verify that this
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transaction was included in a finalized block on chain A, and if successful deposit funds into the
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recipient account on chain B.
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Chain B would need a way to convert from a foreign currency to its local currency. How this is done
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is left to the runtime developer for chain B.
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This module is one example of how an on-chain light client can be used to prove a particular action
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was taken on a foreign chain. In particular it enables transfers of the foreign chain's native
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currency, but more sophisticated modules such as ERC20 token transfers or arbitrary message transfers
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are being worked on as well.
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## Ethereum Node
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On the Ethereum side of things, we require two things. First, a Solidity smart contract to track the
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Substrate headers which have been submitted to the bridge (by the relay), and a built-in contract to
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be able to verify that headers have been finalized by the GRANDPA finality gadget. Together this
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allows the Ethereum PoA chain to verify the integrity and finality of incoming Substrate headers.
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The Solidity smart contract is not part of this repo, but can be found
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[here](https://github.com/svyatonik/substrate-bridge-sol/blob/master/substrate-bridge.sol) if you're
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curious. We have the contract ABI in the `ethereum/relays/res` directory.
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## Rialto Runtime
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The node runtime consists of several runtime modules, however not all of them are used at the same
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time. When running an Ethereum PoA to Substrate bridge the modules required are the Ethereum module
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and the currency exchange module. When running a Substrate to Substrate bridge the Substrate and
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currency exchange modules are required.
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Below is a brief description of each of the runtime modules.
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## Bridge Relay
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The bridge relay is responsible for syncing the chains which are being bridged, and passing messages
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between them. The current implementation of the relay supportings syncing and interacting with
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Ethereum PoA and Substrate chains.
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