Bitcoin Forum

https://blockchain.info/double-spends
Keeps hovering to 13-14 double spend attempts as of 6/10/14.
edit 53 attempts

edit now down to 3 attempts as of 6/11/14

This is the first time I have seen double spends attempts while checking this section of blockchain.
Can someone explain what is going on (I assume a misunderstanding)

I received an email of someone asking me to change the title to double spend attempts, which is correct. I apologize if I made anyone confused, but I to myself was confused about these attempts.

Thanks for all your comments (I read them all for insight on your thoughts)

Probably some central bank trying to do its thing, ie print more money!!!!  :D :D :D

Wow, haven't seen this in a long time.

That is a lot of double spend attempts from a very small set of related addresses suggesting that someone may be trying to game the system or they have a faulty client.  Trying to game the system being the operative word here.  All of the double spend attempts will eventually be dropped.  Notice also that the confirmed spends all have a pretty good number of confirmations at this time.

All the double spend attempts are from only two addresses:

https://blockchain.info/address/19YqDYmfito6Ykc1vhAY1m7AT2vZ3iJUGL
https://blockchain.info/address/1PEUoYFsJCkxv4uw3eTcp4gMsUbaB3zUxk

and the other highly related address is:

https://blockchain.info/address/1EE2HimJwyjcr8RrFGxEd6XwqY2HBoUCwa

Notice "Public Note: Haters make me famous."

So, probably intentional.

Attempt at a little bitcoin Quantitative Easing ;)

How do these double spends work, I always see them when visiting blockchain but I never did understand how do these happen?

Will the double spends be found and correct in a time frame to impact physical sales? e.g. a double spend is initiated at 2 real world shops. If the shop has a 24 shipping policy, having received BTC and they start the shipping process, will the double spend be identified in time to stop the goods from being posted?

There are thousands of transactions a day and the number of these double spend attempts are actually quite small comparatively. There is nothing to worry about.

Only one of the two transactions will get into the block chain.  After a few (6) confirmations in the block chain the one that gets in is there forever and the other one gets dropped.  If you have shipped the product before waiting the 6 confirmations then you might lose the coins.  Just wait for 6 or more confirmations (about 1 hour on average) and then the transaction is perfectly safe.

This is a bigger deal for a coffee shop.  You want to give them the coffee without having to wait one hour.  So there is some small risk of being the dropped transaction if they give them the coffee with zero confirmations.  However, when they sell coffee for VISA there is also the chance that the VISA customer will go back any time in the next 30 days and refuse the charge.

And there are protocol enhancements for zero confirmation transactions in the works.

Is there any detail on these enhancements?

Because the core dev discussion on github seems to be very much going around in circles:
https://github.com/bitcoin/bitcoin/pull/4298

A worthwhile change like replace-by-fee has the side-effect of increasing double-spend risks.

It is good if the double spends show up on the page right ??? it means they obviously did no twork.. if i am understanding correctly ?

This page was broken for several months. Now it works somehow.

The timing sure seems a bit suspicious, what with the whole ghash.io situation.

edit: Oh. If that's the case, could it be they decided to fix the page due to growing concern about a 51% attack?

I was sure that bitcoin is safe from double spends, isn't it?

And it grows...

As long as the transaction is confirmed, yes it is safe from double spends.

Unconfirmed transactions are not safe.

These are all double spend attempts.  There is nothing preventing someone from trying to double spend - but it will never work.

Nothing to worry about, the system is safe.

In fact, OP, please add the word attempts to the title of this thead.  You are freaking out the noobs.

Yes, these are the double spend attempts that have been detected.

Always remember that just because one pool has over 50% of the hashing this does not automatically mean they are going to try to do something evil.  At that point they are earning 50% or more of all the new BTC being created.  Why would they try anything that would kill the goose that is laying the golden eggs for them?  It would be the ultimate in stupidity for the pool to try something like an easily detected attack.  They would not do it.  This is not something I worry about.  

If you are a miner and you are worried about it move to another pool.

Gash.io   is really a gov site on a mission to crash btc..?!?!?

No.

Down to only 3 at the moment.  Again, this is nothing to worry about.  It only shows that the Bitcoin system is functioning correctly (detecting and preventing double spend attempts).

You can see a better view here:

http://54.186.244.42:5984/respends/_design/explore/_list/list1/date,time,hash?descending=true&limit=40

There are basically two sources of double spending weakness right now:

1) Dice sites that fall into Luke-Jr's "spam filter". These dice sites could fix this at any time by just not reusing addresses. It's not a hard change. They could implement BIP70 whilst they're at it and save everyone a lot of resources and money. However, they don't do it, so I guess they don't care about being double spent.

2) The fee drop which isn't working because miners aren't upgrading to Bitcoin Core 0.9 whilst other users are. This is partly my fault, but is mostly due to the totally broken fee market. According to nice and simple economic theory, mining is competitive and miners are supposed to include all transactions no matter what the fee is, because if they leave money on the table, some other miner will grab it. So fees are supposed to be used only for load control. In fact mining is not competitive at all because of pooling and it seems the handful of people who control mining have collectively decided not to allow lower fees, because it's become a real profit centre for them, so they're playing "who blinks first" with wallet authors.

As you should know every transaction you include increases your orphan rate. Prior to the v0.9 fee drop transaction fees were probably already low enough that adding transactions to your blocks actually cost you money, based on careful measurement and analysis done by myself and others; lowering them by another order of magnitude definitely put them below that limit. FWIW I've spoken to some mining pools and large mining operations who have also told me this was their reason for rejecting the 0.9 fee drop.

After all, why risk orphaning a block, worth ~$16,000 USD, when an entire block full of v0.9 transaction fees is only worth $6.50 USD? If they're "leaving money on the table" they sure as hell aren't leaving much.

Also, your double-spend attempt thing is missing dozens of double-spends that I'm seeing on my replace-by-fee nodes.