Why Is a 6-Block Confirmation Depth Considered the Standard for Bitcoin Transactions?
A 6-block confirmation depth for Bitcoin is an arbitrary but historically accepted standard that balances security with transaction finality time. It is based on the probabilistic cost of a 51% attack.
With each additional block, the probability of an attacker successfully generating a longer chain and reversing the transaction drops exponentially. After six confirmations, the cost to re-mine the chain becomes astronomically high, making a successful double-spend economically unfeasible for most attackers.
Glossar
Transaction Finality
Principle ⎊ Transaction finality is the principle that once a transaction is recorded on a blockchain, it cannot be reversed, altered, or canceled, providing absolute and irreversible settlement assurance.
Confirmation Depth
Depth ⎊ Confirmation depth, within cryptocurrency derivatives and options trading, represents the granular assessment of market validation preceding a trade execution.
Required Confirmation Depth
Depth ⎊ Required confirmation depth is the minimum number of subsequent blocks that must be appended to the blockchain after a specific transaction's block before that transaction is considered irreversible and final by a receiving party.