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Sova Labs
February 15, 2025
Protecting the network with a verification-first approach to Bitcoin transactions
In Bitcoin, double spending occurs when the same BTC is used in two different transactions, but only one can ultimately be valid.
For Sova - an execution layer that complements Bitcoin - the challenge is making sure that BTC deposits on Sova always reflect transactions that have actually been confirmed on Bitcoin.
Without safeguards, a user could submit a Bitcoin transaction, broadcast it through Sova, but if that BTC transaction never confirms on Bitcoin, Sova’s state would diverge - leaving it inconsistent or even fraudulent.
To address this, Sova introduces slot locking, enforced by a new mechanism we call Sentinel. Slot Locks are temporary restrictions applied to specific storage slots within smart contracts.
When they activate: A Bitcoin transaction is included inside a Sova transaction.
How they work:
Sentinel identifies storage slots that would be updated.
It checks that none are currently locked. If any are, the Sova transaction reverts.
Otherwise, it locks the slots and records their previous state.
The lock persists until one of two outcomes
The Bitcoin transaction confirms on L1 → the lock is released and the state change is finalized.
The Bitcoin transaction fails or does not confirm within a certain block window → the state is reverted to the recorded value.
This mechanism has strong parallels to the computer science concept of bit masking
Bit masks use binary flags (0/1) to control access to specific bits without disturbing others.
Slot locks use a binary state (locked/unlocked) to control access to specific contract slots without disturbing other state variables.
Just as bit masks can atomically update registers, Sentinel atomically manages slot states, synchronizing them with Bitcoin’s confirmation reality.
Cross-Chain Atomicity – State changes on Sova only persist if the corresponding BTC transaction succeeds.
Revertible Operations – Unlike most blockchain operations, slot locking allows a “pending” state that can safely roll back.
Guaranteed Finality – Within a known block window, the network can provide a definitive answer about whether an event tied to Bitcoin has been finalized.