I just tested the time to cross-chain from the Bitcoin mainnet to the Bitcoin L2 BOB, and it took nearly 1 hour under the current non-congested conditions of the Bitcoin mainnet.
During the waiting time, I read the official BOB cross-chain bridge Gateway documentation. Unlike the bidirectional BitVM cross-chain bridge envisioned in the white paper, the BOB Gateway cross-chain bridge, which is in phase 1, is a light client cross-chain bridge, and due to being built on the OP Stack, data availability verification relies on the Ethereum mainnet.
Below is the lifecycle of the cross-chain TX from BTC to BOB:
1⃣ User initiates a cross-chain request by signing with a native segwit Bitcoin address
2⃣ User transfers BTC UTXO to the LP (currently speculated to be BOB team's) address
OP Return bytecode carries the hash value of this TX
3⃣ BOB runs a light client on the Bitcoin mainnet (tBTC solution) to verify the legitimacy of the hash value attached to OP Return
4⃣ Gateway mints WBTC or swaps to BTC LRT/LST for the user on BOB L2, and updates the state data to be batched for verification and storage on the Ethereum mainnet.
It can be seen that the BOB team is diligently optimizing the time and interaction experience of the official cross-chain bridge, but due to the current first-phase solution stack being limited by Bitcoin's programmability and Ethereum's finality, it is difficult to achieve short-term effectiveness in reducing the cross-chain time of the official bridge.
Unless you complete the OKX x BOB task, you must use the official bridge; otherwise, a third-party cross-chain bridge based on message-liquidity architecture would be recommended.
