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

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The true bitcoin community Top Stories with the Inside take.

"Not Bitcoin-XT" is trying to not let a miner vote take place.

On the bitcointalk forum, a new client called "Not Bitcoin-XT" was recently announced. From the post:
Running this version and/or mining with XT block versions will make it impossible for the Bitcoin XT network to detect the correct switchover and cause a premature fork of anyone foolish enough to support BIP101 without wide consensus from the technical community.
They are literally trying to get nodes on the network which pretend to support the bigger block size patch, but actually don't. If enough miners ran this software, it would falsely trigger the 75%/95% acceptance thresholds.
Fortunately, most miners are known entities and would not be caught dead running software like this. The rest of the users just add to the Bitcoin XT node count, ironically making Bitcoin XT appear to have even more support.
submitted by StephenM347 to bitcoinxt [link] [comments]

Not Bitcoin XT

Not Bitcoin XT submitted by CryptoJunky to CryptoCurrency [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
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
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.
3) "Version bits proposal",
Pieter Wuille, May 26th 2015, Bitcoin-development mailing list, [,](,)
5) "On consensus and forks - What is the difference between a hard and soft fork?",
Mike Hearn, Aug 12th 2015,
6) 2013 San Jose Bitcoin conference developer round-table

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submitted by bitcoin-devlist-bot to bitcoin_devlist [link] [comments]

A bug that allows miners willing to burn 12.5 BTC to crash the Bitcoin Core nodes. BU, ABC, XT not affected!

A bug that allows miners willing to burn 12.5 BTC to crash the Bitcoin Core nodes. BU, ABC, XT not affected! submitted by uMCCCS to btc [link] [comments]

Blocksize Debate: Coinbase? BitPay? Circle? What the fuck do they think about that?

Their silence smells like "we don't give a shit because we have other plans, let the average bitcoiner waste his time and words", even if, because of their HUGE involvement with Bitcoin, they should probably care way more than the average bitcoiner here on Bitcoin.
Personally, as an average bitcoiner, I'm not going to waste tens of millions of dollars if Bitcoin goes to shit. What about them?
Any ideas? Any word from them?
------------ EDIT -------------------
Xapo SUPPORTS larger blocks:
“We support Gavin's proposal as we think it is important for Bitcoin's growth and development to get ahead of this hard cap before it is a problem. Many of us are already circumventing this by processing as many transactions as possible off the blockchain which makes Bitcoin more centralized, not less."
Coinbase SUPPORTS larger blocks:
"Lets plan for success. Coinbase supports increasing the maximum block size" SUPPORTS larger blocks:
"It is time to increase the block size. Agree with @gavinandresen post at 1/2"
BitPay SUPPORTS larger blocks:
"Agreed (but optimistic this will be the last and only time block size needs to increase)"
Coinkite SUPPORTS larger blocks (BIP100):
“BIP 100 is a reasonable proposal, but it must be implemented by Bitcoin Core and not Bitcoin XT.”
BitPagos SUPPORTS larger blocks (BIP100):
“BitPagos supports the increase in the block size. It is important to maintain the Bitcoin network reliable and its value as a global transfer system."
submitted by 1_obvious_throwaway_ to Bitcoin [link] [comments]

Trying to understand the Bitcoin Unlimited philosophy and why there is no malicious intent

BitcoinXT, Bitcoin Classic and Bitcoin Unlimited have caused a lot of anger and “bad blood” in this space. Many have argued that these clients could split the hashrate into two groups, separate the nodes onto different chains, causing effective network downtime and a catastrophic loss in the integrity of the system. However, this does not mean proponents of these clients had malicious intent, they simply view the system in a different way. I came to this realization after reading the following quote from a prominent Bitcoin Unlimited supporter:
The problem is that BIP109 is both a hard fork and a soft fork at the same time; that is, it allows for larger blocks but it adds tighter limitations on number of bytes hashed and number of signature operations. Bitcoin Unlimited supports larger blocks but (at this point in time) does not believe the additional rules should be added. On test net, BIP109 activated and then a block was mined that was valid according to Bitcoin Core and Bitcoin Unlimited, but was invalid according to Classic due to these additional rules, and the Classic nodes were forked off the network. This created some FUD (that in my opinion was misplaced) and now many people think it's better to turn off BIP109 signalling.
To some it may be difficult to believe, that even after the miners had explained the issues to BU supporters and Bitcoin Classic nodes had been booted off the test net due to being tricked into a false activation, the false flagging of BIP109 is still thought as misplaced FUD!
Prior to this I had spent hours trying to persuade Bitcoin Unlimited supporters to remove the BIP109 flag, emphasizing that they effectively doing the bidding of “Not Bitcoin XT” ( I felt like I was hitting a brick wall of ignorance and utter stupidity. However, I realized it is just a different view. If Bitcoin Unlimited supporters are apparently fine with “attacking” their own side, then it demonstrates a lack of a malicious intent in there "attacks" on the "opposing side".
While I somewhat disagree with their logic in this respect, I do not think it is objectively as stupid as one may think. Please consider the following assumptions:
In the above scenario, it is apparent that BitcoinXT, Classic and BU are not attacks on the network. Since the currency is in its early stages and not actually used, any network downtime or double spend attack opportunities caused by the attempted transition to larger blocks are not a problem. Since the network is an idea inside the minds of the community, nodes diverging onto different chains is not a concern as the community will be able to decide on the validity of the chain in a social process and then later update the nodes. Any delays are not a concern due to the above.
The above assumptions are not necessarily false, the system is new and actual usage of the currency is limited. At the same time the network is both a P2P network of nodes and an idea, and the relative weighting of the importance of these two things is not clear.
Therefore Bitcoin Unlimited proponents are neither stupid or malicious, they just look at the system from a different angle. Bitcoin Unlimited have been persuaded to remove the false flag, even if they do not understand why, I at least think they do not see a significant disadvantage of removing the flag, which is ultimately why they made the decision. In this respect the two opposing sides of the community have some common ground. We all need to try and look at the system from many angles, and try to consider the requirement of keeping the network up and running reliably, the actual behavior of the nodes and the vision people have.
submitted by jonny1000 to Bitcoin [link] [comments]

Double Spend Relay in XT was contested by owner Mike Hearn and introduces risks to zero-conf not needed in Bitcoin Cash.

Double Spend Relay in XT was contested by owner Mike Hearn and introduces risks to zero-conf not needed in Bitcoin Cash. submitted by ThomasZander to btc [link] [comments]

Tom Harding of Bitcoin XT: "But sure, it's not worth abandoning BCH over any of these [SV] changes. Following ABC regardless of hash makes much less sense."

Tom Harding of Bitcoin XT: submitted by heuristicpunch to btc [link] [comments]

Bitcoiners: make no mistake! Even though it is very likely that BTU is now going the same way as XT and Classiccoin the re-centralization attempts will not stop.

Bitcoin is a revolutionary approach like never seen before in the history of the world. It is even more disruptive than any revolution seen before as it does not depend on weapons and the beheading of kings but offers an exit from the centralized financial world. It is a truly peaceful revolution that does not need guns and bloodshed and that is not aiming at putting someone else on the throne but burning down the throne altogether instead. Decentralization instead of replacing the central power that is.
Any kind of revolution always triggers a counter-revolution. Re-centralization of the network is the counter-revolution to Bitcoin. In an even more sophisticated way than Xtcoin and Classiccoin BTU is aiming to enable re-centralization of mining, nodes and software development. They even wanted to install a “president” of Bitcoin. No kidding! :)
With every wave the counter-revolutionary re-centralization movement is getting louder and stronger. This one has been exceptionally smart in attracting big miners / pools to it by telling them that they can outcompete and eat the smaller ones. But with every wave Bitcoin is getting stronger and more resilient as well and it has given us the ultimate tools to fight off these attacks: actual, factual decentralization and immutablity of the ledger. That is what Bitcoin stands for. No compromise on that, sorry!
And these attacks will never stop. So even if BTU goes down the drain now please be aware that the fight for your own freedom will never end. “Compromise” like it has been suggested a lot in the recent days is not anything the re-centralization movement wants. It wants perpetual war and perpetual infighting and it will do anything it can do to achieve that and that means that the next iteration of the counter-revolution is already at your doorstep.
Freedom is never achieved for good. Freedom is something you lose when you go to bed at night and that you will have to fight back again next morning when you get up.
Keep on hodling! Keep on running your own node! And maybe even get that old 330 Megahash USB-miner out of your memorability-drawer and hook it back up to the network just to make a point! :)
Edit: added a zero.
submitted by joecoin to Bitcoin [link] [comments]

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

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

Trace Mayer: "I would not be surprised if this current Bitcoin Unlimited, Bitcoin XT, Bitcoin funded by or is some kind of government sponsored attack on the Bitcoin network, and they're not getting very much traction."

Trace Mayer: submitted by rbtkhn to Bitcoin [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]

Annoucing Not-BitcoinXT | jyellen at | Aug 16 2015

jyellen at on Aug 16 2015:
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submitted by bitcoin-devlist-bot to bitcoin_devlist [link] [comments]

As much as I like Bitcoin XT; the 75% supermajority is a major problem. (Because F2Pool)

Let me preface this by saying I am a supporter of Bitcoin XT and even run a node sponsoring / hosting service that has nearly 90 active full XT nodes on the network. I want XT to succeed, and is why I think 75% is too low for a supermajority; it makes us vulnerable.
Some of you might have seen this article on BIP101 flaws and one point sticks out:
It is almost certain that if BIP101 is activated, it will be with a sub-supermajority, or even a minority.
Now, it's not almost certain, but in particular circumstances it is a game killing issue. Take the following:
  1. Two large mining pools could collude to have >= 25% voting power. (F2Pool, BTCChina, and Bitfury hold around 21.7%, 14.1%, 11.2% of voting power respectively).
  2. They are all currently voting for BIP100 and so collusion candidates represent at least 47% of all voting power.
  3. That means potential damage to the BIP101 camp is salient somewhere between 25% and 50% miner support (call it 45% to get rid of the race condition).
  4. If the BIP101 movement were within the 25-45% range and the above three pools started mining on Not Bitcoin XT, then all BIP101 miners (25-45%) will eventually start producing big blocks which would not be accepted into the main chain (because they're only supported by 25-45%).
  5. Since (in this case) Non-BIP101 miners would make up >55% of the hashing power it is incredibly unlikely the BIP101 chain would last long - there would be many stale blocks and it would cost BIP101 miners dearly, until they moved back to Core.
What this means comes back to a generic truth about self-organised systems: minority rule never works.
By selecting 75% as the supermajority threshold we give a wide window of opportunity to a minority to fuck it up for everyone else. IMO this is exactly what we want to avoid, whether that's in regards to core devs, mining support, or w/e. A 95% supermajority would close that window and restrict it to a much larger actor and a much smaller time frame, greatly decreasing the risk of an attack. The only 'perfect' solution is unanimous support but for obvious reasons that is unlikely.
The next question is something like 'can we even get 95% support?' which is a difficult one to answer. Another option is 85% because that would mean the two largest BIP100 supporters listed above would need to collude, or all three.
submitted by 646463 to bitcoinxt [link] [comments]

The hard work of core devs, not XT, makes bitcoin scalable.

The hard work of core devs, not XT, makes bitcoin scalable. submitted by work2heat to Bitcoin [link] [comments]

BU/Classic/XT discussion: banned from r/Bitcoin, "altcoin not Bitcoin". Litecoin threads: just fine! herp derp

submitted by theonetruesexmachine to btc [link] [comments]

Bitcoin Core versus XT observations | Ken Friece | Aug 19 2015

Ken Friece on Aug 19 2015:
1.) Most people are running XT as a vote for bigger blocks and not because
they specifically support BIP101. If Core supported bigger blocks, most XT
users would switch back to Core and XT would die.
2.) In this high stakes game of poker, XT just went all in, but Core still
has the far better hand. There are many, many scaling solutions Core could
adopt that would appease XT users enough to kill XT. Don't let perfect be
the enemy of good. The real question is whether or not anyone can provide
enough Core leadership to reach "consensus". The longer it takes for Core
to reach "consensus", the stronger XT gets.
3.) Bitcoin market price has a far greater mining centralizing effect than
larger blocks ever will. Right now, miners with reasonably efficient
hardware and energy costs (.5W/GH mining hardware, 10 cents per kilowatt
hour power, $250 BTC price) spend about half of their mining income on
electricity. If the total Bitcoin market cap is under ~5 billion at the
next halving in July 2016, it's game over for all but the most efficient
(large) miners. The mining centralization that may occur with 8MB blocks in
2016 is nothing compared to the centralization that will occur if the total
Bitcoin market cap does not grow substantially between now and the next
4.) Investors hate uncertainty, and the blocksize issue is adding a lot of
uncertainty right now, which makes the mining nightmare scenario outlined
above more likely. The entire ecosystem needs time to adjust and grow once
a Core scaling solution is adopted. Hopefully this issue will be revolved
well before the next halving in July 2016 so the market has time to adjust
and grow again.
5.) Not-BitcoinXT is a really terrible idea. Mike has proven time and time
again that he will not blink or back down. The chances of Not-BitcoinXT
gaining 25% of the hashrate are pretty much nil, so in effect, all
Not-BitcoinXT will do is help XT reach the 75% threshold sooner and end up
putting more people on the losing side of the fork.
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I'm amazed we only have ~515 Bitcoin XT nodes running. Guys, let's do more. This is not really difficult or expensive...

Hello fellow Bitcoin XTers,
Amidst all this recent reprehensible behavior by Cobra-Bitcoin, Bitcoin moderation by Theymos, and Bitcoin Core Devs, I decided to do something to try to help out our cause: I'm now running a Bitcoin XT node.
It was incredibly easy to setup, and it's running on one of my underutilized servers.
If you want to express your support for Bitcoin XT and moving Bitcoin forward (past all of the negatives of the status quo), I highly recommend you take this very simple and positive action: Setup a Bitcoin XT node today!
I am truly amazed that (as of right now) there are only 515 Bitcoin XT nodes running. (How is that possible?)
Come on, guys, let's do more. This is not really difficult or expensive... (Honestly, servers are relatively cheap nowadays. No need to try to run this on laptops or Raspberry Pi's, imo.)
submitted by transponder717 to bitcoinxt [link] [comments]

Bitcoin XT is not effective in preventing double-spending attacks of fast payments. We also show that an adversary can perform double-spending attacks—without the risk of loosing money.

submitted by BitFast to Bitcoin [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]

Tom Harding of Bitcoin XT: "But sure, it's not worth abandoning BCH over any of these [SV] changes. Following ABC regardless of hash makes much less sense."

Tom Harding of Bitcoin XT: submitted by ABitcoinAllBot to BitcoinAll [link] [comments]

Negative "Bitcoin XT Trojan" article is surprisingly not censored on /r/bitcoin

Negative submitted by seweso to bitcoin_uncensored [link] [comments]

HOW MUCH CAN I MINING BITCOIN WITH AMD RADEON RX 5800 XT ... Bitcoin XT: What Is It and Why Was It Released? Nick Szabo's Remarks on the Bitcoin XT Fork Mike Hearn's What Is Bitcoin?

Bitcoin Unlimited “follows the release of Bitcoin XT and Bitcoin Classic”. XT and Classic were two previous attempted hard forks that also failed. Like Classic and XT, Unlimited is also supported by a small group of Bitcoin mining pools. With the Remote Exploit Crash bug discovered in Bitcoin Unlimited, the proposal went down the path of failure like XT and Classic. The Remote Exploit ... You are not going to feel that the broker is forcing you in any direction when you sign up with BubbleXt. That’s something you do feel when you sign up with other brokers on the internet. You will be shocked to know that some brokers want complete control of their traders. They don’t let their traders make any move without their consent. In addition to that, they provide their traders with ... Bitcoin XT was a fork of Bitcoin Core, the reference client for the bitcoin network. Skip to content. Menu. Home; Sample Page; Uncategorized Posted on October 4, 2020 October 4, 2020. Bitcoin Regrets: How Much Would $100 Be Worth Today? Bitcoin Regrets: How Much Would $100 Be Worth Today? Mining gives legitimacy to Satoshi Nakamoto’s imaginative and prescient, enabling a decentralised and ... [Not Debunked] Bitcoin XT Fork. I left the most sensitive topic to the end. In the August of 2015 someone sent this email to the dev mailing list from [email protected] I have been following the recent block size debates through the mailing list. I had hoped the debate would resolve and that a fork proposal would achieve widespread consensus. However with the formal release of Bitcoin XT ... Not Bitcoin XT. This is a special fork for those who do not agree with the blocksize scheduled increase as proposed by Gavin and Mike in their divisive altcoin fork, "Bitcoin XT". This version can be used to protect the status quo until real technical consensus is formed about the blocksize. This version is indistinguishable from Bitcoin XT 0.11A except that it will not actually hard fork to ...

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Excerpt from Episode 82 of Epicenter Bitcoin. Mike Hearn describes the "worst case scenario" that could follow after the 20MB block size limit is introduced into Bitcoin XT. Miners (e.g., in China ... Buy A 5700 XT For Mining Now? - Or A Non XT Which Can Be Flashed To An XT? - Download Claymore Miner v15.0 Here -... how much can i mining bitcoin with amd radeon rx 5800 xt ?? for check this item on amazon : for more content subscribe note : we work... Bitcoin Talk Show #LIVE (Sep 2, 2019) - Crypto News Talk Price Opinion with your Calls - Duration: 1:09:52. World Crypto Network 757 views. New Not an expert in anything, just a dude documenting his Crypto Mining journey! A Crypto Mining Bitcoin/Ethereum/Speculative Coin Channel! Thanks for stopping ...