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With proof of work and the associated mining process, transactions must wait till the block verifying the said transaction reaches enough depth within the blockchain to avoid relying blocks generated by an attacker who may have succeeded in creating a temporary fork in the blockchain.

This typically means waiting for several minutes to gain enough confidence that a transaction was genuine.

Is a similar confirmation time required in when consensus is reached using proof of stake rather than proof of work?

  • You should note that a confirmation in Ethereum is not necessarily equivalent to a Bitcoin block, so 6 confirmations may not be enough. – Tjaden Hess Feb 18 '16 at 16:54
  • OK. If 6 is is not enough, then what is considered enough? – zanzu Feb 18 '16 at 16:56
  • I believe Poloniex uses 350, but that's pretty excessive. I would say 100 or so should be enough. – Tjaden Hess Feb 18 '16 at 17:46
  • OK. Do you know what drives the requirement to wait for more blocks on Ethereum vs Bitcoin? – zanzu Feb 18 '16 at 17:53
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    The probability finality is based on how much it would cost to fork the chain from that block. The amount of hash power that goes into a Bitcoin block is far more than an Ethereum block. – Tjaden Hess Feb 18 '16 at 17:56
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Is a similar confirmation time required in when consensus is reached using proof of stake rather than proof of work?

It depends on the Proof of Stake and Proof of Work being compared.

For Casper, the planned Proof of Stake algorithm for Ethereum, the answer is not yet known:

How will the number of confirmations for security change with Casper?

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