Light Client Bridge A bridge between two blockchains connects them together. Some bridges only enable moving assets from one blockchain to another, and some bridges move the whole data of one blockchain to another. The second type covers the first one RELAY Relay is an interoperability solution that makes it possible to access the whole data of the source chain from the target chain. In a Relay, there are parties called Relayers who submit block headers of the source chain on the target chain. A smart contract (Relay contract) checks the validity of submitted block headers by checking the consensus mechanism of the source chain. The smart contract, then, decides which blocks should be finalized according to the finalization rule of the source chain. Therefore, the Relay smart contract that exists on the target chain, acts as a light client of the source chain

Access Cross-chain Data After adding the new block header by a Relayer, TeleportDAO checks for any previous block header that got finalized. When a block header gets finalized on the source chain, it will get finalized on the target chain in a very short delay. Users can refer to finalized block headers on the target chain for proving the inclusion of some data on the source chain.

Bitcoin Bridge TeleportDAOs Bitcoin bridge contract validates the Proof-of-Work mechanism of Bitcoin. For every submitted block header the Relay contract verifies: The block header refers correctly to a previously submitted header. The header shows enough work has been done. Re-targeting the difficulty has been done correctly. Some other checks: the header hasnt been submitted before, the block number isnt too old, etc. If a block header passes all checks, it is considered a valid block header. However, the valid header cannot be used for checking transaction inclusion since it may rewind from the main chain by future block headers.

Finalized Headers Every time a valid block header is added, the Relay contract checks whether a previous block header gets finalized. To do so, Relay uses the longest chain rule of Bitcoin, i.e, a header is finalized if it is buried under six consecutive valid block headers. Users can provide Merkle inclusion proofs against the finalized headers. Also, the Relayers who submitted block headers that become finalized will get a reward.