Bitcoin Blockchain Forked By Backward-Compatibility Issue

New submitter jhantin writes "The Bitcoin blockchain has forked due to a lurking backward-compatibility issue: versions older than 0.8 do not properly handle blocks larger than about 500k, and Slush's pool mined a 974k block today. The problem is that not all mining operations are on 0.8; blocks are being generated by a mix of several different versions of the daemon, each making its own decision as to which of the two forks is preferable to extend, and older versions refuse to honor or extend from a block of this size. The consensus on #bitcoin-dev is damage control: miners need to mine on pre-0.8 code so the backward-compatible fork will outgrow and thus dominate the compatibility-breaking one; merchants need to stop accepting transactions until the network re-converges on the backward-compatible fork of the chain; and average users can ignore the warning that they are out of sync and need to upgrade." Turns out there's an approximately 512K limit to atomic updates in Berkeley DB which were used by versions prior to 0.8. 0.8 uses a new database, allowing blockchains that old versions won't accept to be created.

Comments

Old news.

[NettiWelho]

640K would have been enough for everyone.

Re:Old news.

[Anonymous Coward]

You laugh, but some of the developers, the lead developer Gavin, and another core developer Mike Hearn, are pushing really hard to get the current 1MB limit (7 transactions/second) on blocks lifted so Bitcoin can directly scale to VISA-like volumes.

Never mind that Bitcoin is inherently an unscalable O(n^2) network - every transaction has to be broadcast to every node - and the issue they ran into was also a problem scaling. Mike's solution is to just throw thousands of dollars worth of hardware at the problem. Never mind that for Bitcoin *any* issue the means that some nodes can process a large block, and some can't, turns into the same hard-fork we just saw. Never mind that it will make Bitcoin centralized, and lead to perverse incentives for large miners to attack smaller ones.

You'd think they'd say "OK, hold on, how about we just use ways to transfer funds that don't have to go into this shared state ball of mess?" but no, they're desperate to take the easy way out at any cost.

I really wonder if my Bitcoins will be worth anything in a few years.

Ooh, exciting!

[fuzzyfuzzyfungus]

Why achieve 'consensus' when we could let the fork fester, and have two virtual currencies floating wildly against one another as well as USD?

In fact, why not introduce Bitcoin-0 through Bitcoint-Aleph and let them fight it out? I'll bring popcorn!

Re:Ooh, exciting!

[DrXym]

Just to get the ball rolling...

Post 0.8 users - if you fuck over the people on the earlier bitcoin format, the value of your bitcoins effectively DOUBLES!

0.8 and prior users - if you fuck over the people on the later bitcoin format, the value of your bitcoins effectively DOUBLES!

Just ask yourself what Ayn Rand would do in the same situation.

Re:Ooh, exciting!

[julesh]

Just ask yourself what Ayn Rand would do in the same situation.

Die in penniless poverty while dependent on the state to provide basic income and medical facilities that are necessary to maintain her life, all while maintaining that such a system is inherently evil? It's what I like to think of Ayn Rand doing in *any* situation.

Re:Gobble bobble wobblywob?

[ledow]

Bitcoin is a virtual currency that works by "doing work" (a complicated mathematical "puzzle") on your computer. It becomes a currency by the difficulty of the puzzle, and that when you have solved it you tell other BitCoin users about your success and it goes into a "chain".

That chain is the history of EVERY transaction performed on the BitCoin network and the integrity of the system is given by every user relying on the same chain - so trying to create some extra BitCoins or a fake transaction requires compromising a lot of machines around the globe to believe it happened.

Because of a stupid bug that nobody knew about related to the size of a transaction in this chain, a transaction that's too big for older clients to handle was (legitimately) created. Older clients can't handle it, so they have no idea what to do when it comes into their chain updates. Newer clients can handle it, but can't synchronise their chains with older clients because of it (they can accept the transaction whereas older clients don't).

Because the chain is now effectively split into two chains, and that all the integrity of the system comes from the fact that everyone is using, verifying and updating the same chain, BitCoin is now in an "emergency" (quoted from the forum post in the summary) situation. New clients are generating coins that old clients can't see and vice-versa, so BitCoins are being generated and lost or transacted and forgotten about.

The fix is to go back to the old code, ignore the over-size transaction, and hope to fix the code in a more backward-compatible way. Unfortunately, that requires some people on newer clients to lose coins, revert transactions, and for exchanges to shut down (temporarily) until the issue is resolved.

Basically, someone really messed up by not checking that the database could handle transactions that could pop up in the real-world.

Re:Gobble bobble wobblywob?

[fatphil]

> most major exchanges have already reverted to 0.7

Yet 0.7 is the version with the database bug.

These bitcoins certainly aren't a replacement for gold - they're far too irony.

Re:For those, like me, reading this and saying wtf

[dumael]

The Weimar republic and Zimbabwe suffered massive inflation, not deflation.