Gallery¶
Trustless Bridges¶
A presentation about trustless blockchain bridges built using the Substrate blockchain building framework. Bridges are a way to connect different blockchains without a trusted central party.
Made by Hernando Castano.
You can check out all files here.
Markdown slides:
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# Trustless Bridges
### By: Hernando Castano | @hernando:matrix.parity.io
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---
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## Presentation Outline
- What is a Bridge?
- Types of Bridges
- Rialto Bridge
- Future Plans
---
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## Demo Prep - RLT
---
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## What is a Bridge?
tl;dr: A way to connect two unrelated chains
### Types of Bridges
- Custodial
- Collateral
- Trustless
---
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## Custodial Bridges
[Chain A] -> [Central Party] -> [Chain B]
- You send your Chain A token to the central party
- Expectation is that they will credit your Chain B account correctly
[BTC] -> [wBTC Foundation] -> [ETH]
- Example: Wrapped BTC on Ethereum
---
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## Collateral Backed Bridges (XClaim)
+----------------------+ +----------------------+
| BTC | | ETH |
| +-------+ | | +-------+ |
| 1 | | | 0 | | | |
| +----> | Vault | +--------------> | S.C | +--+ |
| | | | | | | | | |
| | +-------+ | | +-------+ | 3 |
| | | | | |
| | | | ^ v |
| + | 2 | | |
| Alice +----------------------------------+ Alice |
| | | |
+----------------------+ +----------------------+
---
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## Trustless Bridges
[Chain A] -> [Chain B]
- Basically an on-chain light client for a foreign chain
- Light clients only follow headers and keep no state
[Chain A Headers] -> [Chain B]
- A light client will track headers of the source chain
- If applicable, needs to keep track of finality
---
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# Rialto Bridge
---
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## Rialto Bridge
[PoA Ethereum] <-> [Substrate]
- Two way trustless bridge between an Ethereum PoA chain and a Substrate chain
- Ethereum chain is using Aura consensus
- Substrate chain is using Grandpa consensus
- Repo: https://github.com/paritytech/parity-bridges-common
---
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## Authority Round (Aura) Consensus
- Designed in Parity Ethereum days for stable a test network
- Blocks are produced at regular intervals by trusted authorities
- Authorities implicitly vote on blocks by building on blocks
- A block is considered finalized if it has (n/2) + 1 votes
- If we had three validators: (3/2) + 1 = 2
[A] <- [B] <- [C]
| |
| --- Finalized when C is built
--- Finalized when B is built
---
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## Grandpa Consensus
- Authorities are staked
- Authorities vote on chains of blocks which they think are final
- Authority sets change periodically
- Blocks that signal these changes have a special log in the header
```
/ [C1] <- [D1]
[A] <- [B] <- [C2] <- [D2]
\ [D3] <- [E3]
```
---
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## Rialto Architecture
OpenEthereum Node Substrate Node
+-------------------+ +-------------------+
| | | |
| Substrate Header | | Ethereum Bridge |
| Light Client | | Pallet |
| | | |
| | | Currency Exchange|
| Grandpa Finality | | Pallet |
| Precompile | | |
| | | |
| | | |
| | | |
+-------------------+ +-------------------+
---
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## Bridge Relay
+--------+ +--------+
| | | |
| ETH | | SUB |
| | | |
+--+----+ +-----+-+
^ ^
| |
| +--------+ |
RPC | | | | RPC
| | Relay | |
+--> | | <--+
+--------+
---
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## Rialto Applications
+----------------------------------------|
| |
| Currency Exchange |
| |
+----------------------------------------+
| |
| Light Client Base Layer |
| |
+----------------------------------------+
---
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## Rialto Applications
+----------------------------------------+
| |
| Your Application! |
| |
+----------------------------------------+
| |
| Message Dispatch |
| |
+----------------------------------------+
| |
| Message Delivery |
| |
+----------------------------------------+
| |
| Light Client Base Layer |
| |
+----------------------------------------+
---
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## Eth2Sub Header Sync
```
Rialto PoA Bridge Relay Substrate
+ + +
| | Best ETH header? |
| | +------------------> |
| | |
| | I know about X |
| Any newer header? | <------------------+ |
| <------------------+ | |
| | |
| | |
| Yep, here you go | |
| +------------------> | |
| | New headers incoming |
| | +------------------> |
| | |
| | | +----+
| | | | Verify headers
| | | <----+
| | |
| | | +----+
| | | | Import headers
| | | <----+
| | |
+ + +
```
---
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## Eth2Sub Currency Exchange
```
Rialto PoA Bridge Relay Substrate
Lock RLT + + +
+-----+ | | |
| | | |
+-----> | | |
| Any CE Txs? | |
| <------------------+ | |
| | |
| Yep, here ya go | |
| +------------------> | |
| | Tx Inclusion Proof |
| | +------------------> | +-----+
| | | | In finalized header?
| | | <-----+
| | | +-----+
| | | | Credit Funds
| | | <-----+
+ + +
```
---
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# Future Plans
---
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## Future Plans
[DOT] <-> [KSM]
- Want to connect Substrate based chains
- Important for sovereign chain communication
- Potentially implement a bridge parachain
[DOT::Call] <-> [KSM::Call]
- Arbitrary message passing between Substrate chains
[ETH] <-> [DOT]
- Want to connect Ethereum mainnet to Substrate chains
- More of a support role to other teams (e.g Snowfork)
[DOT] <-> [DOGE]
- Who wouldn't want to see this?
---
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# Shout-Outs
Slava Nikolsky (@svyatonik)
Tomek Drwięga (@tomusdrw)
Thibaut Sardan (@tbaut)
