> For the complete documentation index, see [llms.txt](https://docs.bitcoinos.build/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.bitcoinos.build/technical-documentation/grail-pro-charms-zkbtc/technical-overview/grail-pro/grail-pro-operational-workflows/bridging-workflow-btc-less-than-greater-than-zkbtc.md).

# Bridging Workflow (BTC <> zkBTC)

Process: (Full Flow for Bridging BTC and zkBTC):

&#x20; 1\. The user, via the frontend, queries operators for the current roster's public keys and generates a Taproot deposit address (spendable by multisig or user refund after timelock).

&#x20; 2\. The address is submitted to the backend (which can be operator-run; users don't need to trust it as they can perform actions themselves).

&#x20; 3\. Backend detects payment, creates a bridging transaction: for BTC to zkBTC, it locks BTC in multisig and mints zkBTC; for zkBTC to BTC, it burns zkBTC and releases BTC.

&#x20; 4\. Backend sends unsigned transactions to all operators via the message broker.

&#x20; 5\. Operators verify (including ZK-proofs for app contract satisfaction) and return signatures.

&#x20; 6\. Backend aggregates signatures and publishes the transaction upon threshold.

<br>


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