In the original Nakamoto and sBTC whitepapers, there was a proposed design imposing a Bitcoin-block delay of 150 for sBTC deposit and withdrawal transactions. However, with the latest Nakamoto rules, this delay has been removed instead securing these transactions via new miner requirements.
The latest design guarantees that once a Stacks transaction is confirmed, reversing it is as challenging as reversing a Bitcoin transaction. This means the Stacks blockchain is now more secure and stable, with no independent forks.
To accomplish this, sBTC will introduce a new requirement for Stacks miners. Now, they must include both a hash of all recognized Bitcoin transactions that Stacks recognizes, as well as a hash of the block itself. This change is a step up from the current system, where only the Stacks block hash is included.