▪️Bitcoin bridge

The TeleportDAO Bitcoin bridge establishes connections between Bitcoin and EVM-compatible chains, including Bitcoin L2s, while maintaining Bitcoin-grade security. This bridge facilitates the development of various cross-chain applications for Bitcoin, such as Bitcoin and Ordinal wrapping, BRC-20 trading, Bitcoin lending, and Bitcoin-backed stablecoins, among others.

How does the Bitcoin bridge validate data?

To operate this bridge, Relayer nodes retrieve the latest block headers of Bitcoin and submit them to the Relay contract. Initially, these headers are stored as valid block headers and later transition to finalized block headers.

Valid block header

When a block header is submitted, the bridge validates it against Bitcoin's Proof-of-Work rules. The Relay contract verifies that:

  1. The block header correctly references a previously submitted header.

  2. The header demonstrates sufficient work has been completed.

  3. Difficulty retargeting has been executed correctly.

  4. Additional checks ensure the header hasn't been submitted before and the block number isn't too old.

If a block header passes all checks, it is considered valid. However, there is still a chance that a valid header may be excluded from Bitcoin. It remains permanently on Relay if it becomes a finalized header.

Finalized block header

Each time a valid block header is added, the Relay contract verifies whether a previous block header has been finalized. To do so, Relay applies Bitcoin's longest chain rule, meaning a header is finalized if it is buried under 6 consecutive valid block headers. Once a block header is finalized, it remains on Relay indefinitely. At this stage, the Relay contract also rewards the Relayer who submitted the finalized block header.

The Relay contract prohibits Relayers from submitting block headers at a height where a finalized header already exists. Relayers can only submit block headers belonging to a height greater than the last finalized height.

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