Proof of Stake is a proposed modification to the Bitcoin protocol.

maaku claimed that it doesn't require a hard fork / alt chain.

Is this true?

3 Answers 3


It depends on what PoS system is considered (or not, since I think the answer is the same either way).

Cunicula's system is completely different from what we have now. There's no way to "half" switch to it since a block which is valid in the current system means nothing in his system, and vice versa.

My system uses a skeleton which resembles the current system, so in theory you could solicit signatures in parallel and let anyone use them or not as he pleases. As theymos says a fork will still occur once there's a disagreement between the two systems about which is valid; and anyway, I think the process of collecting signatures and embedding them in the blockchain requires enough rethinking of the network that it is meaningless to regard it as anything but a hard fork.

Of course, even if you make an entirely new alt for it, you can always provide a built-in mechanism to allow bitcoin owners to import or copy their wealth, to make sure the early adopters of decentralized digital currencies at large don't suffer from the advent of a new and potentially better alternative to the original Bitcoin.

  • 1
    lol - A big "import wealth" button :)
    – ripper234
    Jul 31, 2012 at 14:00

If proof-of-stake is adopted and someone succeeds in attacking proof-of-work but doesn't meet the new proof-of-stake rules, the network will split: old clients will go with the attacker and new clients won't. So I would say that proof-of-stake is a hard-fork change. A fork might be avoided if no one tries this attack, but you can't rely on that.

This doesn't mean that you can't do the change without causing chaos, though. A totally backward-incompatible change occurred in February without much turbulence, for example, though this change required two years of planning in advance. A similar gradual roll-out could be done for something like proof-of-stake.

(I don't actually think proof-of-stake is a good idea.)

  • 2
    Thanks. Why don't you think it's a good idea?
    – ripper234
    Jul 31, 2012 at 8:52

Depending on the implementation, it might not require a hard-fork (which is defined as old clients not following the ongoing blockchain). If all POS-enabled blocks also have valid POWs, old clients will accept them too. This is similar to the BIP16 rollout last March.

I'm not sure proof-of-stake is a good idea, since it gives even more power to computer crackers who steal a lot of Bitcoins, and forces miners to keep their Bitcoins online for mining. It also could lock a lot of smaller miners out.

  • Why would it lock smaller miners out? The same computer crackers can hack into mining pools and abuse them to perform a double spend ... we can continue this discussion on the PoS thread: bitcointalk.org/index.php?topic=68213.0
    – ripper234
    Aug 7, 2012 at 5:02
  • I don't think POS requires to have the bitcoins online. If you design the protocol well, coins that are used for mining, will have two keys associated with them, and the one used for mining can't be used to spend them. Aug 7, 2012 at 10:19

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