Bitcoin Forum

EDIT: I'm not trying to imply deepbit.net has any such intentions!

Looking at http://bitcoinwatch.com/ we can clearly see that deebit.net mining pool has acquired the biggest minority share of the total hashing speed of the entire network. It's almost 50%.

So I was wondering if this isn't a dangerous situation since who ever has control of a client with half or more of the total hashing speed could with a good chance start attacking the Bitcoin system with fraudulent double spending?

they have no incentive to do so other than screwing with the system, and even if they did they couldn't do much.

People seem to trust the operator, so the risk seems smaller. There was/is some discussion about this on the official Deepbit thread (the one you arive at when you click the "Forum" link on their site); the operator himself seems to be working on finding a solution for this concern.

I can see another threat:

Imagine that difficulty went to +150k and suddenly the deepbit pool went down, e.g. due to attack or malfunction. I tried several other pools, but these have problems. Many low-par hashrate users would not dare "to mine on mine" = solo, so the effect may be that there will be drastic delays between each new block found. The transactions would slow down a lot.

Concentration of the power of net into single pool is bad thing, imho.

If they start attacking the system we will just DDOS them!

Btw I wasn't trying to imply anything bad about deepbit.net. I realize it's not in their interest to start performing fraudulent and harmful actions if they want to keep their customers. I just wanted to point out the facts and hear peoples opinions.

Probably because of what you say i have transactions sent paying fees with 0 confirmations for 24hrs...

Where are my coins? They disappeared from my wallet and never arrived to where i sent them, so WHERE ARE THEY?

Yes, having a single instance with >50% is bad for the network, deepbit just happens to be the first ever to reach that limit. I'd encourage people to start creating new pools. Having slush's pool down (for whatever reason) should provide you with enough users to justify investments :)
And hopefully slush's pool comes back up soon :)

Actually no, the difficulty is adjusted each 2016 blocks, so a sudden drop right after an adjustment might take really long to have an effect on the actual difficulty (if we are left with 25% of the hashing power it takes up to 8 months to adjust the difficulty)

There is an incentive for an entity to ddos every public pool after a sharp decrease like that. They could then more easily mine while taking out all competition.

I set up a pool miner for the first time this morning on the computer of my wife (a gamer, so she a better card then I have). I also chose deepbit.net, because someone else mentioned it to me before. It would be nice to have a good comparison sheet, comparing all the pools besides each other on various points.

If you want to compete with deepbit, xf2.org (see signature) offers pool service that scales with traffic.

There have been numerous comparisons made, but as the pools, and their features, change constantly, it's difficult for anyone to stay on top of it.

Here are some basic comparisons based on what I know of the pools:

Deepbit.net
3% or 10% fee (pay-per-share vs. proportional)
Fastest Pool
Most users (meaning payments are split more ways)
Long Polling
JSON stats (using API auth token)
Mints it's own transactions into it's own solved blocks
Email notifications (not sure what though)

Slush's Pool (mining.bitcoin.cz)
2% (up to 6% at user discretion) for score-based shares, which favors faster cards that submit shares more frequently.
2nd Fastest Pool
2nd Most users
No long polling
JSON stats (using API auth token)
Mints it's own transactions into it's own solved blocks (I believe)
Email notifications on payments

BTCMine.com
0 - 5% fee (don't know if it's forced)
3rd Fastest Pool
Long polling
JSON stats (using API auth token)
No clue about transactions
No clue about email notifications

BitcoinPool.com
No fees
4th Fastest Pool
Long Polling
JSON stats
Private Forum
Mints transactions into it's own blocks
Transparent stats for all users
Email notifications for payments, block solves, account changes

Eligius
Fairly new, I don't know too much about it, but you can read about it in their forum post.

...and I'm sure there are others.

On BTCmine...

Voluntary donation once the pool was closed last week.  The voluntary is still in effect
E-mails on payouts, miners down, blocks found, and much more!

xf2.org pool

- 0.45 BTC/month flat fee, no percentage
- long polling
- web stats
- payouts go to xf2.org account balance
- 24/7 monitoring, in case of server problems

(or you can start your own pool, and set your own rules)

For clarity's sake, is the fee 0.50BTC/month per client, 0.50BTC/month taken off the top of all earnings, or etc?

I don't understand how the "billing" of the fee would work.

Edit: When would the fee be taken as well? First round of every month? If so, I'd just work a different pool for that round.

The fee is the xf2.org account fee, which must be paid 6 months in advance (3 BTC).  That gives you access to the pool servers for six months.

All earnings are then credited to your xf2.org account, which you may withdraw at any time.

Edit: Fee is 0.45 BTC/month, due to continued exchange rate increases.

I have more important features :)

• No need to wait for 120 confirmation blocks, instant payment is possible
• Paying for invalid blocks too

Tycho told me it could't happen any time soon and that he wouldn't allow it to happen.  Then when faced with the prospect of it happening, he changed his tune.  I like his pool, but refuse to use it until he delivers on his promise.  He has an ethical duty to make sure his pool cannot be a tool to attack the network, and setting up a redundant pool [one in the US and one in Germany I believe] is hardly a defense; especially against a government who can easily hit both [it is not as if Germany and the US hate each other, but they may both hate bitcoin].  

I like what Tycho has done, but I think he is letting greed get the better of him and is willing to blind himself to the possibility of what could happen due to his inaction.

I have been suggesting to people to consider BTCMine as a better alternative to slush and frankly, miners have a duty to take workers away from deepbit.  He said himself that he believes in the market and that individual miners should do it.  Show him that individual miners can [I think most are ostriches with their heads in the sand and won't move though, proving him wrong, which I hope I am wrong about].

The hash rate won't go down when difficulty goes up.  The blocks will get bigger [on average] making it harder to find the solution.

He has barely been able to keep it functioning for some time.  I think he may be giving up on it.  Tycho is supposedly going to call him and help him get his pool running again.   Do you think this is a good thing?

Thanks, guess I'll be a bit shopping around then. A + for you!

Eligius is always open to more miners... (https://en.bitcoin.it/wiki/Eligius)

I found another problem with +500 GHash/sec on deepbit.net. As soon as your client miner lower its total participation (for example, 1 GHash equals to less than 0.2 % now), you may get *UNLUCKY* at the moments, when the pool is *LUCKY*.

When there is a block found using just few shares (like in 1 minute or less), your client may not get even the single share "in" and you get NONE reward. Its pitty, cos if your client would be a bit faster, you will score and earn more per day.

For last 24 hours, I can feel about 10% lower yield. May be due unlucky day, but the above may count for it, too.

No, you would not. It all averages out. Slow miners have the exact same chance per MH/s to get a share into a short round as fast miners.

Ah, but you have forgotten all the short rounds where you DID get a share in, and your proportion was much higher than normal.

..most of these people are not ready to be unplugged. And many of them are so inert, so hopelessly dependent
on the system, that they will fight to protect it.
Were you listening to me or looking at the woman in the red dress?
Look again.

Someone, who is 10x faster than me, has 10x higher chance to score during fast found block. When we both hit the fast block, he gots about 10x more than me.

However, when I miss the block completely, my profit is not 10x lower than his. Its exactly *ZERO*.

Its like rounding to cents error, but you can earn only fractions of cent.

http://www.reddit.com/r/Bitcoin/comments/h6ccf/ok_reddit_mining_server_is_running_register/

Reddit Pool - brand new, probably needs a lot of work done before "production ready"

What is this mythical "attack" that everyone keeps alluding to? Does anyone have any real details about what could possibly go so wrong or are they just regurgitating the same paranoid BS arguments that everyone else is? So far I've seen a much bigger list of what Tyco can't do to the network than what he could with >= 50% power. He doesn't own the protocol and he can't change it's behavior. So far the best argument is that it is centralizing hashing power and if it goes down the network will be affected. It's a decentralized P2P network, it will recover. More to the point, anyone who is regurgitating this argument will lose their convenient income, and that is really what it's about.

If I was in his position I wouldn't want to have >= 50% power because this exact thing happens. The petty, jealous, and paranoid come out of the woodwork because their worried about a central entity having control over their income and try to disguise it in some thinly veiled reference of being able to attack the network, with no details whatsoever. You either believe in the power, agility, and ideals that were put into the bitcoin network and the protocols or you don't, either way makes you a hypocrite. If you don't like deepbit being as big as it is, chances are you're part of the problem and free to leave anytime.

Like I said in the other thread Tyco, congratulations on being so successful that you're hated. Keep doing what you're doing and keep up the good work. I know it's an uncomfortable position for you and I'm sure this will all go away as soon as Slush gets back up to speed.

My real life investment club has a rule where no one person can own more than 25% shares in the club... and I think this is a good thing.

Seems to me this pool situation is not what was originally intended and one person or group controlling 50%+  of the total hashing power is a potential issue. I don't like potential issues in a curency system.

It's not an investment club, no one bought in. It's a service and the users are the ones creating the so called "potential issues" and "problems". Users don't own shares in deepbit and they're free to cash out and leave anytime but they don't because it's a good service.

Don't blame the service provider when the users are the one's causing the "potential issue".

Didn't say it was an investment club.. it was a comment on control over a group effort (bitcoin)
Deepbit was not mentioned.

If you're part of a group effort and have voting control then you can vote to change the circumstances, if you don't then your options are participate or leave. I won't mention deepbit either. ;)

Double spending... see http://www.bitcoin.org/bitcoin.pdf

Also +1 for Eligius... low frills, low fees :)

Correct me if I am wrong but isn't the heart of the matter that if somebody controls 50% of the hashing power they can take over the system.

 I am using the voting only as an analogy to control of the entire bitcoin system . It seems like you think I am an idiot and I am thinking because I am getting "shares" on a round  I own part of a pool or should have voting rights or something ..We are talking about two different things

There is no way to "take over the system" with just a high hashrate pool/miner. Please read: https://en.bitcoin.it/wiki/Attacks#Attacker_has_a_lot_of_computing_power

Read Satoshi's paper for an explanation.
He then explains how such an event is extremely unlikely under the assumption that (probability an honest node finds the next block) > (probability the attacker finds the next block)
This falls apart when one person controls >50% of the network's hashing power.

So from what I understand it works like this:
In case of a blockchain fork, the longest chain is considered the valid one, and with >50% hashing power, you can generate blocks faster than the rest of the network. Therefore, you can force a fork from an earlier block, catch up with the rest of the network, and still have your chain end up being the longest one. This invalidates all blocks on the other side of the fork and reverses the transactions included in those blocks.

This did not sound good from that link
"However, if this attack is successfully executed, it will be difficult or impossible to "untangle" the mess created -- any changes the attacker makes might become permanent."

I have no beef with anyone but money is about trust

And now that deepbit is slightly over 50% of the global bitcoin hashing power he's going to take his honestly earned wages and try something like this? *sarcasm in case it wasn't clear* He does not own 50% of the hashing power outright, it is given by the users of the pool. If I were in his position and wanted to be evil I would push the fee up from 3% to 5-6%, much more profitable, easier to accomplish, right out in the open, and doesn't have the possibility of messing up the block chain and impeding future earnings.

I agree. I just answered your question, I'm not accusing Tycho of anything ;)

The question was dramatic for a reason, to disarm all the illogical statements and topic.

I have been around long enough to read and understand the concept of double spending. The document (even though it's not clear in the wording) is talking about someone owning >= 50% of the network hashing power directly under their control vs just controlling a pool with >= 50% of the hashing power of the network. It also relies on being anonymous. If the block chain gets screwed up and the majority controller is anonymous then it's hard to pin on someone. If someone detects a problem in the block chain in a situation like this, guess where they're going first?

Is it possible? Yes.
Is it a imminent threat? No!

Possible way to help with this situation:

http://bitcointalk.org/index.php?topic=7622.0

The issue is double spending.  The ability to spend the coins that the pool receives and then use the computational power of the pool to rebuild the chain faster than the original and spend that money again [i.e. thus issuing the pool members bitcoins that turn up invalid].  If you have more than 50% of the hashing power at your disposal, it is possible to spend a LOT of coins and then rebuild the chain [even longer] and spend it again.  It is very unlikely in a pool that anybody would know that it has happened until received payments showed up as invalid.  Nobody is suggesting that Tycho would do such a thing, but it is always advisable when talking about money that anybody may do anything.  After all the only way to be effective is to appear "Good" until the trigger is pulled (using Tycho as an example, however, Tycho in the Deepbit scenario would be the first investigated and thus, I think the least likely to do such a thing).  In reality though, I think the fear is that a hacker/cracker may break the system (pool), learn how it works, build the attack and launch it when the time suites them and in a manner to collect the rewards [i.e. cash out a large amount of bitcoins at high prices, attack the system, wait for the coin value to drop as trust in the bitcoin fails from all those who find their payouts invalid] and either keep the money or buy back into the market at a low price .. shorting the coin].  Clearly, work would have to be done to do this without detection, but due to the nature of the bitcoin and the route taken from coin to fiat currency, the trail may be hard to follow, especially if distributed.

The point is that pools are the OBVIOUS tool to rob the bitcoin.  One large pool is a very alluring target from outside, but, a couple of colluding pools [or a couple of simultaneous attacks against those pools to commit this crime].

So, does Deepbit (or Slush for that fact) have industry leading security analysts constantly making sure the pool is secure and not being prodded, poked, altered, prepared, etc?  I VERY HIGHLY DOUBT IT since Deepbit hasn't been in existence for very long [no pool has].  Thus, the vulnerability is very real.  Will it happen?  I hope not.  Could it happen?  Absolutely.  Will somebody be tempted to look into it?  Absolutely.  Hackers break into the highly secure military and government computers all the time and they have been powerless to completely stop it.  I don't think Deepbit even remotely has the ability to see it coming little enough stop it should a dedicated attack happen.  Market cap is nearly $24 million USD now, so what will it be like in 6 months?  How much money could an attack yield at that time?  Yes, somebody will eventually find the motivation to at least consider the idea and start down the path (right now, I doubt somebody could get away with more than $20K (US) under the assumption that Deepbit has a day worth of BTC rewards on hand).  The market cap has quadrupled in a matter of weeks.  What happens in months?  The ability to transfer money in and out is going to become easier.  Security for these pools will become VERY important; in particular for the LARGE pools (especially if there are only one or two large pools). 

So, has anybody identified who is responsible for all the DOS attacks against so many pools?  Suddenly Slush is down and Deepbit hits 50% (essentially consumes Slush's miners).  A test attack?  A real attack?  For the purpose of testing this scenario?  Probably nothing so nefarious, but it certainly could be.  The one benefit of this I think is that some of the smaller pools are growing now and I HOPE that those that went to Deepbit to weather the storm will go back to Slush when things are working and secure [or go to another pool] since Tycho changed his mind about allowing allowing his pool to exceed 50% (and just said it couldn't happen for a long time only days ago .. clearly not thinking to far ahead about security in my opinion).

As long as there is an extremely large pool, I would be careful about how much hard currency is put into the market in an attempt to inflate it.  There may be some group out there waiting for the bubble to grow large enough to pop the bubble using the Deepbit pin (using the last 24 hours as an analogy).  With two major pools out there, everybody knows that knocking out Slush will inflate Deepbit ... so don't be a pawn if this happens again.

In summary, the bitcoin market is not ready for a large, relatively unsecured pool and the miners are simply worker ants following the sugar and the large pool a potential weapon if not secured TIGHTLY.  As the market cap grows, the risk becomes greater as the profit motive increases.  This is very unfortunate that this had to come up, but it did.  If Deepbit had gone down, this could just as easily be about Slush's pool.   We now know that taking down one large pool in a market with two large pools making up more than 50% of the hashing power is enough to drive the other pool up in size to the point of being the victim of a separate attack used to execute this scenario. 

When dealing with money and markets, a sharp dose of cynicism is very healthy.

Assume the worst ... any problem with this analysis?

How does decentralized get centralized so quickly?

The biggest pool had some technical troubles and stopped working. The majority of people flocked to the second biggest pool and it became the biggest pool.

Deepbit was bigger than slush before slush's recent problems. It was right around the time of the infamous OCN thread that deepbit became the biggest. So people from the second biggest flocked to the biggest.

Hi,

I had no time to read all entries of this thread. Sry, if I double post this idea.

How about strengthen the single mining?

Especially in my case I would like to mine only with my own miners without any use of pools.
But I have the problem that I can't run my hardware 24/7. So if I would start now I must stop it in a few days for several private reasons and start hashing from scratch again. :(
So I have no chance to get ever a block computed under these circumstances.

Is there any chance to build up a local pool (maybe with dynamically starting and stopping hardware components) which preferably saves the last working state to start from again at a later time?
Unfortunately I have not seen any papers or any source code on this topic yet and I don't know how I could get a running pool daemon. I don't understand the "poold" sources because I'm pinched for time and I haven't found any documentation about it.

Since I'm new to bitcoin and I own no actual hardware I have only 0.25BTC left for a possible bounty.

By nature, the search for block DOES NOT USE ANY STATE. Once you finish one share, you start from scratch on another.

Simply the difficulty controls how its needed to be lucky to find a block. After found block, the chances are the same.

Hey Hawkix,

You didn't understand me. The solved block is not the problem.

As far as I know a miner starts with a nonce. Then it hashes until it reaches a break condition. After that it checks the computed hash:
If it is a possible solution it sends the block to the network and starts a new computation with a new nonce.
Otherwise it drops the last nonce and starts again with a new one.

Only if the sent block is accepted by the network then it sends 50 BTC back to the address where the block came from.

If I did not make a mistake these computations don't need to start from scratch every time a miner is started if there could be saved the last state before quitting (maybe used nonce plus iterations plus last computed hash).

EDIT:
I forgot the most exciting point of my request. If I could split the big computation into smaller problems it would be possible to start and stop at will with my hardware. I would only need a completely headless microcomputer as small server for sending packets and collecting the results (like deepbit, slush and co. already do with their mining pools).

Why is it that the more you talk, the more i think you want to use that in a botnet? :o

PS: In case someone wonders what triggered my comment: it was the part where he says he doesn't own hardware in his first post...  ::)

PS2: If that's not the case, sorry! ;) Maybe i was just doing a little too much outside of the box thinking! lol

Hey psy,


First of all please read carefully since I wrote:
The main message lies on 'no actual'. To be concrete I own a Club3D Radeon HD 5550 with 512MB GDDR 3 and loud noises of the whole terminal in my point of view. On Linux I run at average 43 MHash/s and an efficiency of 0.5 MHash per watts in second.
Sorry if I had expressed my situation wrong (I'm not a native english speaker).

I would be thankful if there would be a way that I don't have to mine 24/7 or joining a mining pool. For this job I could get a headless microcomputer (ARM-CPU) which could be a small server which coordinates the whole computation process. That's what I was guessing of.

How could saving the mentioned state help a botnet?

What I don't think you understand, bill86, is that working on blocks is more like playing the lottery than building a tower.  You don't ever get any closer or further away to solving a block--you just play more or less lottery tickets that give you a chance of solving the block.  With really fast hardware, you can play lots of lottery tickets really fast and decrease the average time of finding a block.  But when you actually find the block is random, so starting and stopping doesn't set you back.  You can play the lottery tickets any time without what you have or haven't done so far affecting your chances of winning.  Make sense?

True enough, searching for blocks is a practically stateless process. You only need an up-to-date block chain to start trying. Getting your block chain up-to-date if you've been offline for a day or so, only takes a few minutes (downloading and verifying the blocks).

There's also one more thing in bill's post which I'd like to clarify:

Strictly speaking, the network does not immediately "send" back anything like a reply. The rules of the Bitcoin protocol specify that the creator of the block *is* the owner of X bitcoins, and currently X equals 50.

The generator of the block claims ownership of 50 BTC, and the network confirms this in future blocks, which become available when generated, very likely by someone else. Future blocks will only confirm this *if* the generated block does verify as mathematically valid.

Those future blocks will however, eventually be downloaded by the generator of the block in question, and do serve the purpose of confirming that the network is accepting the generator's ownership of the coins.

P.S.

Getting back on topic, a single pool exceeding 50% of network capacity is a reason for concern. Good luck to alternative pool operators, I'll try to keep working as a solo miner. I can wait... I can wait very long... and I can run without interruption. Sadly not everyone can.

It furthermore appears that human nature is at work against decentralization here. Since people set out to generate blocks for a reward, they want certainty of getting *some* reward. This can only lead to pooling up, whether in smaller or bigger pools.

If people got accustomed to mining as a mostly-no-reward activity which *may* result in sudden, unplanned luck, perhaps they would be more inclined to mine alone.

Some day, it will need to start happening, and the everyday way of acquiring bitcoins will be buying them. (What happens when the block generation awards become so small that transaction fees start dominating, I won't try to predict.)

All ... it is time to take public action to convince miners that it is not in their interest to allow Tycho to break his promise [again] and allow Deepbit to take > 50% of the hashing power of the network.  Tweet, post on Facebook, whatever you do, get the word out to move to other pools keeping all pools under 50% and ideally, most pools of significance at somewhat equitable size.  We can't have the threat of Deepbit being used as an attack against bitcoin.  With the price going up and people buying hardware like crazy, he is making money quickly and doesn't seem to care about the risk to the network or his previous promise which he already broke once and rationalized it away.  At some point sooner than later if the price keeps going up, an attack will be worth enough money that it will likely happen if there is a tool to do it.  We already know that when Slush went down, Deepbit flew over the 50% mark.  That means now, that he would potentially exceed 60-65% should a similar situation [say a intentional attempt to take down Slush to drive people to Deepbit and then use Deepbit for the attack] happen again!  If a determined group crackers deepbit and uses it for the double spending attack, bitcoin is done; in my opinion, not diminished ... DONE.

Sorry to say this, but have you ever tried to do maths before?
I'll make it simple.
You said "However, when I miss the block completely, my profit is not 10x lower than his. Its exactly *ZERO*. "
So, he has 10*your shares.
Your shares = 0
10*0=0.
Do we understand?
I think you may need to have another maths lesson with my year 1 teacher.

An analogy for those who claim to have no math problems, but still have:

Imagine shooting from a rifle to a train fast passing by. My rifle is 10x slower than yours. So, while a train passes, on average, you will get 10x more hits on it than me. However, if my rifle can shoot only once a minute and there is fast (or short) train, you can hit it .. once or twice, while I may happen than I completely miss it.

Understand now?

That isn't maths. That is so crap example that has almost nothing to do with maths.