Failed Hard Forks of Bitcoin: XT, Classic, and Unlimited

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AUG 19 DIGEST: First Bitcoin Block in Support of Bitcoin XT Mined; BTC Price Plunges Over 13% to 2-Month Low

AUG 19 DIGEST: First Bitcoin Block in Support of Bitcoin XT Mined; BTC Price Plunges Over 13% to 2-Month Low submitted by MuchBitcoin to MuchBitcoin [link] [comments]

Cost to "sabotage" the blocksize hardfork? Just $200,000 per day.

With an nVersion supermajority rule (as proposed by Gavin in January) the hardfork can occur with just 80% of the pre-fork mining capacity on Bitcoin-XT (w/support for a larger blocks) and 20% of the mining still occurring on the side where the 1MB blocksize limit is enforced yet.
We know from experience with pool hopping and altcoin mining that miners will switch to whichever chain provides the best return. "Sabotaging" the hardfork should be possible then by simply subsidizing mining on the original chain (where the 1MB blocksize limit is still enforced) with the intention of attracting enough hashing power to it such that it causes "catastrophic consensus failure" (i.e., two persistent chains), or just as bad -- causing the original chain to eventually overtake the hardfork chain.
So let's calculate the cost of performing this attack. Even if there was nobody else that wanted to buy these newly mined post-fork bitcoins (BTCs mined by those following the protocol of Bitcoin Core v0.10.x and earlier), the attacker could offer to pay above the spot rate for the newly mined Bitcoin-XT (BTX) coins. With 20% of the hashing capacity on the 1MB limit side, that means there would be ~30 blocks per-day on that chain. The block reward subsidy is 25 bitcoins per-block. If this were to happen today, with an exchange rate of $230, the attacker pays $172,500 for the day to buy every bitcoin mined on that 1MB side of the fork. To give an incentive to get miners to switch, let's say the attacker commits to paying 15% above the spot price that the Bitcoin-XT mined-coins (BTXs) are fetching. So that means the attacker pays ~$267 per bitcoin. And that brings the attacker's cost to ~$200,000/day.
Of course, if hashing capacity returns to the original chain then the result is that blocks mined there will start occurring at a faster rate. If the attacker still remains the only buyer of these bitcoins from the 1MB limit blockchain the per-day cost of supporting this attack does rise -- up to a maximum of ~$500,000 per day at which time the attacker's "goal" has been reached -- the hardfork fails with less than 50% of combined hashing capacity.
Of course, I'm making some assumptions that favor my argument. For my numbers to work, I'm presuming the hashing capacity post-fork is essentially the same as it was pre-fork. If instead a KNCMiner, for example, were to blast new hashes that had previously been kept offline so that these hashes now mine the hardfork side, they do have the ability to make this attack more expensive. I'm also projecting today's exchange rate as the rate for the post-hardfork Bitcoin-XT mined coins. Nobody today knows if those will trade higher or lower (or much, much lower even) than the $230 level today's bitcoin trades at. I've also not made any guess as to how many days this attack would need to be be performed before it either succeeds or fails (i.e., hashing capacity on the 1MB side drops and the original chain dies). I will say that if more than just a trivial amount of hashing does return to the original chain then I do sincerely believe the confidence in the hardfork succeeding drops real fast as a result.
So, ... you still want to hand over your private keys to this Bitcoin-XT client by "upgrading" to it? (or worse, keep your coins at an exchange, custodial E-Wallet (like Coinbase), etc. when the hardfork occurs?) I've just explained why there are 200,000 reasons it just might not be a good idea.
submitted by sgornick to Bitcoin [link] [comments]

CLTV/CSV/etc. deployment considerations due to XT/Not-BitcoinXT miners | Peter Todd | Aug 19 2015

Peter Todd on Aug 19 2015:
Deployment of the proposed CLTV, CSV, etc. soft-forks has been recently
complicated by the existence of XT(1) and Not-Bitcoin-XT(2) miners. Both
mine blocks with nVersion=0x20000007, which would falsely trigger the
previously suggested implementation using the IsSuperMajority()
mechanism and nVersion=4 blocks. Additionally while the
XT/Not-Bitcoin-XT software claims to support Wuille/Todd/Maxwell's
nVersion soft-fork mechanism(3) a key component of it - fork
deadlines(3) - is not implemented.
XT/Not-Bitcoin-XT behavior
Both implementations produce blocks with nVersion=0x20000007,
or in binary: 0b001...111
Neither implementation supports a fork deadline; both Not-Bitcoin-XT and
XT will produce blocks with those bits set indefinitely under any
circumstance, with the proviso that while XT has a hashing power
majority, blocks it produces might not be part of the Bitcoin blockchain
after Jan 11th 2016. (though this can flap back and forth if reorgs
happen)
Curiously the BIP101 draft was changed(4) at the last minute from using
the nVersion bits compliant 0x20000004 block nVersion, to using two more
bits unnecessarily. The rational for doing this is unknown; the git
commit message associated with the change suggested "compatibility
concerns", but what the concerns actually were isn't specified. Equally
even though implementing the fork deadline would be very each in the XT
implementation, this was not done. (the XT codebase has had almost no
peer review)
Options for CLTV/CSV/etc. deployment
1) Plain IsSuperMajority() with nVersion=4
This option can be ruled out immediately due to the high risk of
premature triggering, without genuine 95% miner support.
2) nVersion mask, with IsSuperMajority()
In this option the nVersion bits set by XT/Not-Bitcoin-XT miners would
be masked away, prior to applying standard IsSuperMajority() logic:
block.nVersion & ~0x20000007 
This means that CLTV/CSV/etc. miners running Bitcoin Core would create
blocks with nVersion=8, 0b1000. From the perspective of the
CLTV/CSV/etc. IsSuperMajority() test, XT/Not-Bitcoin-XT miners would be
advertising blocks that do not trigger the soft-fork.
For the perpose of soft-fork warnings, the highest known version can
remain nVersion=8, which is triggered by both XT/Not-Bitcoin-XT blocks
as well as a future nVersion bits implementation. Equally,
XT/Not-Bitcoin-XT soft-fork warnings will be triggered, by having an
unknown bit set.
When nVersion bits is implemented by the Bitcoin protocol, the plan of
setting the high bits to 0b001 still works. The three lowest bits will
be unusable for some time, but will be eventually recoverable as
XT/Not-Bitcoin-XT mining ceases.
Equally, further IsSuperMajority() softforks can be accomplished with
the same masking technique.
This option does complicate the XT-coin protocol implementation in the
future. But that's their problem, and anyway, the maintainers
(Hearn/Andresen) has strenuously argued(5) against the use of soft-forks
and/or appear to be in favor of a more centralized mandatory update
schedule.(6)
3) Full nVersion bits implementation
The most complex option would be to deploy via full nVersion bits
implementation using flag bit #4 to trigger the fork. Compliant miners
would advertise 0x20000008 initially, followed by 0x20000000 once the
fork had triggered. The lowest three bits would be unusable for forks
for some time, although they could be eventually recovered as
XT/Not-Bitcoin-XT mining ceases.
The main disadvantage of this option is high initial complexity - the
reason why IsSuperMajority() was suggested for CLTV/CSV in the first
place. That said, much of the code required has been implemented in XT
for the BIP101 hard-fork logic, although as mentioned above, the code
has had very little peer review.
References
1) https://github.com/bitcoinxt/bitcoinxt
2) https://github.com/xtbit/notbitcoinxt
3) "Version bits proposal",
Pieter Wuille, May 26th 2015, Bitcoin-development mailing list, [http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-May/008282.html,](http://lists.linuxfoundation.org/pipermail/bitcoin-dev/2015-May/008282.html,) 
https://gist.github.com/sipa/bf69659f43e763540550
4) https://github.com/bitcoin/bips/commit/3248c9f67bd7fcd1d05b8db7c5c56e4788deebfe
5) "On consensus and forks - What is the difference between a hard and soft fork?",
Mike Hearn, Aug 12th 2015,
https://medium.com/@octskyward/on-consensus-and-forks-c6a050c792e7
6) 2013 San Jose Bitcoin conference developer round-table

'peter'[:-1]@petertodd.org
00000000000000000402fe6fb9ad613c93e12bddfc6ec02a2bd92f002050594d
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submitted by bitcoin-devlist-bot to bitcoin_devlist [link] [comments]

[Question] How does BitcoinXT manage the transition to 8MB blocks?

I know there is some magic threshold when 750 of the previous 1000 blocks have the BitcoinXT version flag set. What happens then? Do BitcoinXT nodes reject blocks that don't have that bit set? Do BitcoinXT mining nodes immediately start producing blocks larger than 1MB? Is there a grace period to allow users some time to switch once it appears the transition is inevitable?
These kind of questions haven't been talked about much that I've seen (at least on Reddit), and I think they're really important in terms of managing the risk involved in forking the blockchain.
submitted by dmdeemer to bitcoinxt [link] [comments]

"Bitcoin XT will implement BIP135 and collaborate with other implementations to allow direct activation of forking changes by a supermajority level of mining defined for that activation."

submitted by throwawayo12345 to btc [link] [comments]

You can support the ABC/BU/XT chain by purchasing a mining contract at bitcoin.com. Most likely this will not provide a return on BCH, but give you a smile every time you see a bitcoin.com block in the chain.

You can support the ABC/BU/XT chain by purchasing a mining contract at bitcoin.com. Most likely this will not provide a return on BCH, but give you a smile every time you see a bitcoin.com block in the chain. submitted by newhampshire22 to btc [link] [comments]

“Interesting that @DavidShares stands by his choice to not list Bitcoin SV as a client of Bitcoin Cash on /r/btc when it is currently mining a large percentage of the blocks. Weird how close this mirrors how XT was viewed in /r/Bitcoin way back.”

“Interesting that @DavidShares stands by his choice to not list Bitcoin SV as a client of Bitcoin Cash on /btc when it is currently mining a large percentage of the blocks. Weird how close this mirrors how XT was viewed in /Bitcoin way back.” submitted by spy_22 to btc [link] [comments]

Oldie but goldie: Mike Hearn's bitcoin parting blog has an excellent summary of history of blocksize debate, core's roadmap, RBF, key players, mining centralization, bitcoin XT, forum censorship and much more.

Oldie but goldie: Mike Hearn's bitcoin parting blog has an excellent summary of history of blocksize debate, core's roadmap, RBF, key players, mining centralization, bitcoin XT, forum censorship and much more. submitted by hunk_quark to btc [link] [comments]

Major Mining Pools Make a Stand Against Bitcoin XT Fork, Support for BIP 100 Grows

Major Mining Pools Make a Stand Against Bitcoin XT Fork, Support for BIP 100 Grows submitted by tylev to Bitcoin [link] [comments]

You can support the ABC/BU/XT chain by purchasing a mining contract at bitcoin.com. Most likely this will not provide a return on BCH, but give you a smile every time you see a bitcoin.com block in the chain.

You can support the ABC/BU/XT chain by purchasing a mining contract at bitcoin.com. Most likely this will not provide a return on BCH, but give you a smile every time you see a bitcoin.com block in the chain. submitted by ABitcoinAllBot to BitcoinAll [link] [comments]

Interesting that @DavidShares stands by his choice to not list Bitcoin SV as a client of Bitcoin Cash on /r/btc when it is currently mining a large percentage of the blocks. Weird how close this mirrors how XT was viewed in /r/Bitcoin way back.

Interesting that @DavidShares stands by his choice to not list Bitcoin SV as a client of Bitcoin Cash on /btc when it is currently mining a large percentage of the blocks. Weird how close this mirrors how XT was viewed in /Bitcoin way back. submitted by ABitcoinAllBot to BitcoinAll [link] [comments]

Interesting that @DavidShares stands by his choice to not list Bitcoin SV as a client of Bitcoin Cash on /r/btc when it is currently mining a large percentage of the blocks. Weird how close this mirrors how XT was viewed in /r/Bitcoin way back.

Interesting that @DavidShares stands by his choice to not list Bitcoin SV as a client of Bitcoin Cash on /btc when it is currently mining a large percentage of the blocks. Weird how close this mirrors how XT was viewed in /Bitcoin way back. submitted by cryptoallbot to cryptoall [link] [comments]

"Bitcoin XT will implement BIP135 and collaborate with other implementations to allow direct activation of forking changes by a supermajority level of mining defined for that activation."

submitted by ABitcoinAllBot to BitcoinAll [link] [comments]

And we have a new mining pool! btc♡xt | Bitcoin mining pool

submitted by Windowly to btc [link] [comments]

What is better, joining a XT mining pool or purchasing a 21 bitcoin computer to mine BIP 101 blocks?

What do users do who want to help raise mining BIP 101 blocks but don't have professional mining hardware?
If enough people have the same goal (BIP 101), can't we get a substantial percentage of hashing power?
submitted by dappsWL to btc [link] [comments]

Support bigger blocks by mining Bitcoin XT with p2pool

Support bigger blocks by mining Bitcoin XT with p2pool submitted by windsok to bitcoinxt [link] [comments]

Major Mining Pools Make a Stand Against Bitcoin XT Fork, Support for BIP 100 Grows. Uh oh... Is XT going to fail???

Major Mining Pools Make a Stand Against Bitcoin XT Fork, Support for BIP 100 Grows. Uh oh... Is XT going to fail??? submitted by ether_economist1 to bitcoinxt [link] [comments]

Chinese Mining Pools Call for Consensus; Refuse Switch to Bitcoin XT

Chinese Mining Pools Call for Consensus; Refuse Switch to Bitcoin XT submitted by Huobi-USD to Bitcoin [link] [comments]

Major Mining Pools Make a Stand Against Bitcoin XT Fork, Support for BIP 100 Grows

Major Mining Pools Make a Stand Against Bitcoin XT Fork, Support for BIP 100 Grows submitted by ziggamon to bitcoinxt [link] [comments]

Chinese Mining Pools Call for Consensus; Refuse Switch to Bitcoin XT

Chinese Mining Pools Call for Consensus; Refuse Switch to Bitcoin XT submitted by btcdrak to Bitcoin [link] [comments]

So this is me trying to discuss bip101 without saying bip101, Bitcoin XT, or /r/btc on the /r/Bitcoin mine-field.

So this is me trying to discuss bip101 without saying bip101, Bitcoin XT, or /btc on the /Bitcoin mine-field. submitted by Brettc286 to btc [link] [comments]

02-23 20:22 - 'You read wrong. I did XT and classic before I did BU, in that order. For your interpretation, there would need to be a comma after "xt". / What would you suggest mining towards if you wanted to support on-chain scaling?' by /u/px403 removed from /r/Bitcoin within 2-7min

'''
You read wrong. I did XT and classic before I did BU, in that order. For your interpretation, there would need to be a comma after "xt".
What would you suggest mining towards if you wanted to support on-chain scaling?
'''
Context Link
Go1dfish undelete link
unreddit undelete link
Author: px403
submitted by removalbot to removalbot [link] [comments]

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