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The side chain/relay does not rely on a trusted third party to help it verify the transaction, but the receiving chain verifies itself after getting the sending chain data. That is, A can read B, but B cannot read A; if a C chain can read all chains, it can logically become an "on-chain" intermediary, and the whole process is "A-C-B". The side chain expresses the relationship of more chains, and the relay is more like the dispatch center of multiple chains. When a "side chain" links many main chains, it becomes a relay chain.
The side chain needs to anchor the other party's data.
Example: Binding: BTC wallet initiates a transfer transaction with an amount of 0 to a multi-signature address, and writes the address of chain B in the OP_RETURN operator. Chain B accepts the light node block of BTC and verifies whether the transaction of the user's chain B address exists (a monitoring mechanism similar to a filter). If it exists, the B chain address is bound to the BTC address.
Deposit: The btc wallet sends money to the multi-signature address of the B chain, and the B chain monitors through the SPV, and the recharge amount is bound to the B chain address to complete the cross-chain transfer
Withdrawal: After the B chain multi-signature and multi-private keys are passed, it can be transferred back to the user's BTC
Core Technology:
SPV certificate
SPV proof: simple proof of payment. Merkel tree verification is carried out by downloading the header of Bitcoin or Ethereum. The root hash is obtained by continuously calculating the hash of a transaction, which proves the existence of a transaction
