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I lost 2 btc on updown.bt - I wouldn't have even known if my local block chain had become corrupted and I was forced to re-download the chain.

When I re-downloaded the chain I was 2 BTC down. I checked transactions and found that a few gambles I made on updown.bt - the 'winnings' were dowble spends.

Here's an example...

tx:79ac7a63ecc1c9357b6b8c69b5e4738de8977ac72b916af4cb0d7f61a2266dad

Clicking on a few links shows the payout in red - my 'winnings' were a double spend.

This is pretty bad for BTC - how do I know that BTC I receive is real?

Twats

You could have known as that transaction never shows any confirmations

I'm telling you this is something new - the transactions that won over the last two weeks from updown are all showing payment 'n/a' - when I follow through the sent transaction numbers I see 'warning this address is using double spends'

This is shit - follow through these txs

2cda7b3fc5d1a4773376f80b4211d8a4dd3a8b70c75c37e34e684169e7749514  (sent 0.1123)
1c5ec45d5d8294c568cc3f950cfbf9f64b03d08986f3399c935a7aadade8597f
2cda7b3fc5d1a4773376f80b4211d8a4dd3a8b70c75c37e34e684169e7749514

There is no problem with any of the above transactions... u r making some mistake. No double spending at all !!! Please provide us screenshot.

https://www.flickr.com/photos/125077066@N04/14577098696/

Please provide the image link. Cant see the address here. Or upload it in imgur.

I'm not sure what to look for in any of the transactions posted. It sounds like your wallet removed the balance associated with transactions that have been unconfirmed for a long time.

It is a screenshot of 12AaGnt5QT2N4Wxv6JP7i7ejSYRcm7nmRh on blockchain.info

https://i.imgur.com/U5INaaW.png

your links look fine to me, you have a problem yourself.  Stop spreading crap, EVERYONE told you on the other thread that only YOU ARE SEEING A DOUBLE SPEND MESSAGE

Hey dick face - see the imgur link

https://i.imgur.com/U5INaaW.png

Im really pissed of you, you are posting all shit, and you are mad only because you lost 2 btc gambling, stop your gambling habit instead of posting this shit, you have posted this almost in every section of the forum.
Someone already said that a double spend tx never gets confirmed. and only you are getting that error msg

"dick face" that's nice.  Grow up, I'm just telling you you're the only one seeing that

you lost too much BTC on the site, that's why you're mad. Take a deep breath and get away from gambling for a bit.

ok - bit upset - sorry about that - still something new and wrong here

These txns were confirmed OK over the last 2 weeks - no doubt about it - only when I reloaded the block chain did I find this problem

I'm actually inclined to possibly believe you because I'm in the updown sig campaign and something funny appears to be going on with that.  

If you check my post history - I wouldn;t post ike this unless I thought there was something seriously wrong here...

Well... now I can see and compare things. Here is my explanation...

U saw the message when the Tx was not confirmed. Blockchain.info somethimes show this when multiple unconfirmed Tx are going out of an address, which is normal from a real time gambling site. Now, u saw that first.

Here begins the second part. Blockchain.info is distributed by cloudflare. Cloudflare catched that message as static against your public IP and hence keep showing it to u even when the Tx has got confirmation.

...This is what I understand out of the whole fiasco... may be wrong. If it is correct, then u log out, have a drink, have sleep, come back after a few hour and login ...u'll see everything is fine with this address... Just like what we are seeing now.

What txids do you have that were confirmed up to two weeks ago, but suddenly were not? Nothing appears to be wrong with any of the txids you have given in this thread.

These txns were over the last 2 weeks - I havent been on updown for 3 days - all of the winnings txns from them over the last two weeks are showing payment address n/a and when I click thoough the txn ids on block chain I keep getting the 'double spend' warning in the image I posted.

I now find that when I refresh the page the warning disappears - but then I click on a few more red links and find another. Even more worrying. And my wallet is 2 BTC light at the end of the day - so there is a BIG warning sign here.

I assume, OP is a non-tech guy. He is talking about Tx and posting addresses !!! We should consider the last Tx associated with these addresses.

use http://blockr.io/ to do search ... presentation is more clear than blockchain.info that it display too many information ...

Actually I am a Technical Architect with nearly 30 years of programming experience.

Checking that now thanks

It says that the address is associated with TXs that contain double spends

Finally - someone sees it too.

TRUE   2014-07-04T00:51:46   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0112   0f4aa5c4b4fae418ffcebbebbf17a7e9a2911b98d228654fcc2bcd4205ab7d93-001
TRUE   2014-07-04T00:51:46   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.01   89ca64029d6fd1cdcca7a21cabd1083b55e44b2a8a96d4d3bfcbaf197d49d195-001
TRUE   2014-07-04T00:51:46   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0126   8cd19af527aec80393a5040a6bf13fa5a2d6182f7c4db475c2d838898ee74210-000
TRUE   2014-07-04T00:51:46   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0192   b01867cf2925b63933c2dae173f794468a76fe2cf9cd411590ea34c2a4e9e9a5-000
TRUE   2014-07-04T00:51:46   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0124   fdb675c5a5112b0bcfe410a1eb0487e53a5c464f09c5978eade3e4c26d84ec56-000
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0126   3317f45915b6477db5a017018e6a05805f1bb599c03f76c0b63eb752c9f3a0d2-001
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0109   be56fd28c114990ad3fa2a2de0857b1c03313a7dd66b5d967777d04661e4696b-001
TRUE   2014-07-04T00:40:41   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0141   dc73bd0f81f9504b6b60cea90b6ea8348d043ec78a036d09de57339c61ab038f-001
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0133   2d92644028275d3c59c195d85608a4a4e6d83de4e4e003fc942c4313a0c3d3ae-000
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0167   41e8a12a9a647b6795baeff6e8aa76baab44bc69923d991fe54cb29c51c7e7e3-000
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0124   46213c93aa992fec817b3452683c749a4b87013f40722e2f891b6863e51a55a3-000
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.01442   92001a06a4d2fa6bcb4457115c9f845ae8e8e8465de75c27eaf41f26e18bd293-000
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0112   9f51e2fc439d898d161f0ff06551060328e7b232720a7755a2969bb8ebac74f4-000
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0122   c6349e1d853b9e8ff5cc473716b8ffc446e85570301deea45ce4e67fbfc6f7ae-000
TRUE   2014-07-04T00:40:41   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0131   f11c0e04c991863d9e9bdc8b1506623d94fa70287be5aee88c6685d151778e62-000
TRUE   2014-07-04T00:09:18   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0101   275dcc1dbd8162dcceaab858b4f4036a9c94e89fb01a85942c020640390bd53a-000
TRUE   2014-07-04T00:09:18   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0144   a677617d5375a8edd8791b9f9295c2fe684c76c6bc06301a6c47281e6799853f-000
TRUE   2014-07-04T00:09:18   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0129   ca6ef8ea7e268040d56347e2ddf30fc06734902d1b81582e1ffff6eae9bc7ae6-000
TRUE   2014-07-04T00:02:10   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0111   60f5f0ea4579dfda47970af9f0befe895f4e79f1be2e150307015c1a5fbd3ad9-000
TRUE   2014-07-04T00:02:10   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.01331   d50235e7689ee4d318c2b56b0410d6afcae85263567b661c6470ff0deb546ad5-000
TRUE   2014-07-03T23:57:22   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.01112   05b6ab47065ef36ab2e8fb4e8dc3df035485c1fb958fc0cc0978f08a486a9ff0-000
TRUE   2014-07-03T23:57:22   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0121   55d6eb96a9a2e80d4ece11f76976e045767c7d5c9bd03bb48d6546b458e88aeb-000
TRUE   2014-07-03T23:57:22   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.01117   96e51b2c2ca24140d3b30c38325d87a6e4a51e7e03fe1346e999800ccfe21d75-000
TRUE   2014-07-03T23:54:26   Sent to      1M6WomNYaDCbbTGfh1wQyJ5esd9YbeF6CW   -0.0104   60779f53e8f5462ef7b2d1fb165318e3ecb143f04883b86e522285c24029deac-000
TRUE   2014-07-03T01:22:49   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.01312   0e676bf58179ac729d84591820ecd9e94e9e03498d2726f9a18503c89c92ab5a-000
TRUE   2014-07-03T01:18:15   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0103   ebb489d0d8be415d5d1d7ad865a8a9d1ac9c24d4495d61857974f52718ad8927-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0101   32db3b5d114945eeece1d1776b49b75ab005d716112306fbb69397c6eecdca7f-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0239   394c8420f5031a7faf9b7eb469665e56ef1f4efefd264909437ce34fb360a8a6-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0122   47d3dadff41f1e70186975204fee46ef2549844618064844e389c11d22d67a94-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.013   5d7b728261c64178f4bd718b7dfc989f529464dd10ee73c0ff246ea575e6c9ab-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.013   6d5c29b514860de4730a489313816319b9d3f566f06fff40587fabc4171411de-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0218   7ff402d96e842b66fc511be46c9e1294eef5f955607ced8bab763e158a74693e-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0212   c04a955c71bc1a2c7a00e4c7b2e23b4398e2c16b6941a07642fcd98fbeb6e24d-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0154   d62342c6a3c1baae19cda7c493d3f1195a2ca5425d97494119e7790ad2b081d7-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0126   e2c24f5247858ef29457afd0d2340ec2cf4fbe8adcca49c67430cb4d0d6f2ed1-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0136   feec587d9567a45e648d52a08dc10fbb9309b2060b7f413f0c01fb7182951558-000
TRUE   2014-07-03T00:46:35   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.02442   ff7e86595d9fd831de5f70e7e9aca4768f60a2359e8664ada66f7df477ab18f5-000
TRUE   2014-07-03T00:16:45   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.1001   b18f119fd2d7bf64ba5d27268d8923d586da3dd80c3c065af8d5a1057e425981-000
TRUE   2014-07-03T00:16:45   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.02333   d1449ec6fcd46747fa6f37724b940dc2ffd25afd396b40ebcfdf47bcce0b2349-000
TRUE   2014-07-03T00:16:45   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0501   d23908f50d053955df0bf7ee264b290ff54e7f171310a8b419106b8ed4f007f0-000
TRUE   2014-07-03T00:16:45   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0401   f272bf70f2fa4a636d31afeca50c55d1497dad3f7a2c5936d04aadb69a1b96db-000
TRUE   2014-07-03T00:11:48   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.044632   529776bd3cf9cc85185a792bac7268196de8b470f48f5be14b8926e3176344e6-000
TRUE   2014-07-03T00:11:48   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.0111   621fc6ad648900773216b988949af61978c5bf11f35ffb88c77fdbce9f9c867a-000
TRUE   2014-07-03T00:11:48   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.015   956bbc5a271362b6650de331b4e0db7b66c59752253c95b223f74d213283c740-000
TRUE   2014-07-03T00:11:48   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.031732   c97e5556dbf9a7ea10b1f358a3bbe5bdc37723768b90d2c6f7342af3e859bff2-000
TRUE   2014-07-03T00:11:48   Sent to      1Ms44T9PWUsSfrBibN9jLJqcJUbfpM689p   -0.01866   d4789fda7cd78c0b2a63270d04ba0311d4821c0f88d63ffb956c44f586353b91-000

Hes not saying he sees that message typing manually the address, he SAID what your picture says, and he is saying that BECAUSE bitcoindream said he cant see the image.

http://images.sodahead.com/profiles/0/0/2/4/9/4/0/8/3/homer-simpson-face-palm-71013262034.jpeg

https://i.imgur.com/wTPwlu4.png

another one

Oops ....I dont have even 1/10th of that :P

Anyways... u may check uR addresses on these block explorers...

https://www.biteasy.com/
https://chain.so/btc
https://helloblock.io/
https://bkchain.org/btc

Oh man !!! He said it completely on a different perspective. Looks like u r determined to take the price down with 'double spend' ghost, buy some coin and sell them later to make up your 2 BTC loss !!!

An double spend attacked wallet...

https://i.imgur.com/TdZfNG1.png

So your wallet got attacked not those addresses.

Just so happens that only the updown txns are affected? unlikely...

Can u plz specify something ? Which one is affected according to your belief ?

1. Transaction

2. Address

3. Wallet

Point out what you define "double spend" on that screenshot of your wallet, it seems like you dont know what can be a double spent

Because if you saw some of your balance dissapear is because the tx dint go trough well and it was returned to the sender, this kind of txs never gets one confirmation, so in this case they have to send it to you again. this is an uncommon error of the clients not double spending.

updown cant double spend anything! only if you have more than 51% of hashing power you can do it, educate yourself

The transactions that updown.bt made to me (my winnings) were double spend txns. They appeared in my wallet just fine but when I was forced to re-download the blockchain, those txns were marked as 'double spends' on the block chain.

I don't have the txns in my wallet for the receiving coins any longer. But I do have the txns that I made to place my bets. Those are the txns I listed above. You can follow the path of a bitcoin on blockchain info so I searched it to see where my coins ended up by following my own payment txns. By doing this I get warnings that the addresses I was sending to were performing double spend attacks.

Basically I can't trust what's im my wallet - it might be showing perfectly fine, but if I re-download the blockchain then it may disappear - this is bad shit.

Ok, I'm pretty sure you seen my images from block chain and the image from my wallet - if you can't see a problem here then carry on - enjoy.

update

The operator of those addreses can be doing something real scammy, im reporting now i can see that error too

https://bitcointalk.org/index.php?topic=600446.msg7726721#msg7726721

Well if this is true, wow, and why wasn't this caught by anyone earlier?  It would have a big impact on the sig campaign as well.

now it dissapeared, but i can testify that i saw that error on address https://blockchain.info/es/address/16AxyGBRFQt1FETWtYNVGJFyv6udU6V3ER .

not sure if its a bug from blockchain or there is something wrong in those addreses

Forget Sig campaign. If double spending can be done so easily, Bitcoin will crash tomorrow.

Well my wallet is 2 BTC light - so it's not an anomaly - it's real...

Yeah - that's my point!

It was always my understanding that anyone could double spend, you didn't need to have 51% hash power or whatever.  That's why you have to wait for a confirmation or two, right?

So now explain this carefully..

You got 2 btc as a payment from updown right?

They dissapeared when you tried to send them to another address?

how many confirmations did you got on that tx, the bitcoins you received?

show the amount you did receive from updown and show the address where you received it

Time for Death and Taxes to make a surprise appearance.

No, these were small txns over the last two weeks adding up to 2 BTC 'winnings' - some of these txns has hundreds of confirmations showing in my wallet. Only when I re-downloaded the entire block chain did I find the problem.

Ok...so I'm not alone who is badly missing him now.

I'm also missing Gavin, Theymos, Danny Hamilton, Gweedo.

Need them on this thread... NOW !!!

z
Yes I got 2 btc as a payment from updown right? - in small txns over the last 2 weeks

No, they disappeared when I was forced to re-download the entire block chain

Hundreds of confirmations on the older txns

I can't show the received amounts as those txns are no longer in my wallet - but I have posted the sent txns - and if you follow them then you get the double spend warning.

So if you had like lets say 5 btcs in your wallet, the ones who dissapeared could have not been the updown ones, did you verify if you dont have any 0 confirmation tx in your wallet recently? maybe the 2 btc amount missing is from other txs

No, the only other txns are from mining at slush's pool - and the total I have remaining matches the total when I add up the payments from slush's site. The only missing txns are from updown.

I'm not sure how I'm going to be able to accept a txn as verified now...

Lol so we need some forensic investigation in here, but why are not more users of updown complaining about it?? or is because they havent spend the amount received?  :D
In that case he could have gone over localbitcoins and sold thousands of dollars of btc worth or sell bitcoins even at cash in person.

Would be interested to see if any other 'winners' can spend those coins...

http://nottm28.imgur.com/all/

Sorry - made them publically viewable now...

This is quite concerning if you can receive a double spend with over 100 confirmations. How??

The album is missing. Please reload it. I would like to research this myself. This fits into a Ghash.Io casino attack senario I'm researching.

they work for me, here are they

http://i61.tinypic.com/vexbpg.jpg

http://i60.tinypic.com/11jch21.jpg

Post the txid of the transactions that you claim are problematic.

Not saying whether OP has a legit complaint, however I would point out that it appears that the updown sig campaign is a total scam.

FYI, also check out updown's post in the updown thread on July 1.  It says their wallet was cleaned out recently due to double spend attack.  Wow.  Maybe they are trying to get back at people who stole money from them with double spending?

Yeah, so who are making this vicious attacks? and how are they making them?

Thanks

When I checked this morning the missing txns were back - http://nottm28.imgur.com/all/

I think someone noticed a double spend attack from updown and somehow suspended all txns from the last 2 weeks. Now they have been released.

This is some scary shit...

So the reason for the anomaly is still a mystery or it has been discovered ?

Bitcoin crash ? so is this the right moment for change myself and all my Bitcoins to FIAT ?  :'(

It was an issue with his wallet not showing all the transactions. The blockchain.info warning he was seeing on some addresses doesn't necessarily mean anything.

Nah I'm not willing to believe that - it was only the updown txns that were affected - if was a problem with my own wallet then why with only updown? Also I only saw the double spend warning with txns associated with updown. You explanation is far from satisfying.

It is not possible for select transactions, with many confirmations, to suddenly become unconfirmed in the blockchain and then disappear from your wallet. There is no way to "suspend" the transactions like you have suggested before. They either are confirmed or unconfirmed. Do you have an issue with a specific transaction? If so, what is the transaction id (not the address) and what problem do you think exists?

Also, as I previously stated, that warning you may see on blockchain.info doesn't necessarily mean anything.

Well I also thought it was not possible to unconfirm a transaction that had hundreds of confirmations - but it must be possible. Isn't that what they did when the blocked chain forked last year - they rolled back to a point in time and all txns up to that point were lost.

As previously stated - I no longer have any issues with any txns. I did have an issue yesterday and I posted a large pile of txn ids if you actually want to read the thread.

Also as previously stated - the fact that you state the warnings I was seeing regarding the missing updown txns does not necessarily mean anything is far from satisfying. They could mean something and you stating that they might not doesn't add anything. Unless you actually knew what they meant. Which you dont.

So all of my questions remain unanswered.

[edit] see for yourself here

http://nottm28.imgur.com/all/

That is why I used the word selected. It is not possible for one specific transaction in a block to become unconfirmed while the rest in the same block are unaffected.

I looked at some of the transactions, but did not see any issues with double spending, even when you were still experiencing the problem yesterday. I admit I did not look through them all or maybe I missed something.

That blockchain.info warning shown on an address (it doesn't appear on transactions) can happen when unconfirmed coins are spent and blockchain.info thinks they may never be confirmed. The warning went away because the transaction(s) in question received a confirmation. (If I am wrong about the blockchain.info's warnings, please let me know.)

The only difference in the two wallet screenshots is one (https://i.imgur.com/TdZfNG1.png (https://i.imgur.com/TdZfNG1.png)) is missing transactions that the other (https://i.imgur.com/fyQCrWR.png (https://i.imgur.com/fyQCrWR.png)) has listed. It seems the wallet fixed itself after the corrupted data issue was resolved and it was fully synced.

What questions do you still have?

Other people clearly stated they could also see some of the double spend warnings - I wasn't seeing things - so maybe you did miss it.


Most of the transaction ids I posted had already been confirmed, some in their hundreds. How can the block chain think a txn with hundreds of confs might never be confirmed?


As above, the txn(s) in question were already solidly confirmed. So why was the warning there in the first place for a well aged txn?


I restored the wallet from a backup and resynced the last weeks worth of txns - it didn't take long to fully sync - yet hours and hours later the updown (and only the updown) txns were showing n/a for address and txn id. And these were the addresses showing the double spend warnings.


1) Can a set of transactions to a specified btc address be reversed?
2) If so, how is that done?
3) If so, who does it? - and under what circumstances?
4) If so, how secure is the process? Is it susceptible to a malicious actor?
5) What is the trigger for blockchain.info to show this double spend warning for an address?
6) Can I be sure (even after hundreds of confs) that a payment I recieve has really been recieved?
7) Would you be so nonchalant if you were watching txns disappear from your own wallet?

8. How can I (if at all) defend myself from someone performing a double spend attack when sending me coins?  (like the OP topic states)

That blockchain.info warning may have been in error or maybe your browser was loading an older version of the page from its cache. Blockchain.info is just a website and has been known to have issues from time to time.

Your wallet was probably not finished, or it would have shown all the transactions correctly.

Once a transaction receives a confirmation (is included in a block), it is irreversible.

See:

If I knew they already had confirmations, I would know it is an issue with my wallet. While it may be annoying or take time to fix, I know my coins would be there.

Don't rely on the transaction until it is confirmed. Once it is confirmed, it is yours until it is spent.

You can't do it. The system is supposed to do it for you. Rational actors are supposed to preserve the system but as we all know people don't always live up to our version of rational.

I don't believe you were the victim of a double spend. It's more likely that your original bootstrap.dat file became corrupted. You then downloaded it over the corrupted copy adding to the problem. Did you finally delete the old copy of bootstrap.dat or rename it bootstrap.old? If I were you I would save my wallet.dat file, delete all Bitcoin folders, download a fresh copy of QT, copy over the old wallet.dat, and resync with the network.

Your guesses are useless and give me nothing - I'm hoping someone who actually knows something might answer (some of) my questions...

Yesterday I thought I was the victim of a double spend. Today all seems well. That's a bit worrying on its own for me - one day broke next day fine no explanation kind of thing.

When I got the corrupt wallet message I said yes - re-download the entire chain. After I while I got bored, shutdown the client and restored my \AppData\Roaming\Bitcoin folder (after moving the existing one out the way) to a backup I took 7 days ago. When I fired up the client, it said 7 days out of sync as expected. Everything looked normal. As the last 7 days came through I was noticing that the updown txns were showing n/a for txn id and address. Just updown. I can understand if a client is not synching random txns - but this was only the updown ones. Slush and other payments I have sent and recieved were all shoing fine. Getting worried, I block chained some of the updown txn ids and found these double spend warnings. Others seen them too from their own browsers when they checked out the txn ids I posted. That rules out browser cache. That rules out me being an idiot. I welcome your theory but it doesn't give me any kind of warm feeling...

[edit] I back up my wallet.dat file to offline once a week too - but since I restored the entire bitcoin folder I didn't do anything manually with the wallet.dat

I suppose I shouldn't have wasted my time with "useless" answers. Insulting people trying to help you usually doesn't get you far...

No insult intended - but you seemed to be repeating the same thing with no apparent knowledge of what you are talking about...

Multiple people are trying to explain u with reasoning. I'm sorry to say, that your adamant attitude is extremely unwelcome.

Well I'm sorry you think that - but "ah it will be OK" doesn't help me and I'm frustrated that no-one seems to know the answers. We all just 'hope' that "ah well it will be OK"...

Anyone who probes is obstricised. I don't mind standing out and asking the questions that we should know the answer to but - we don't.

Under the right circumstances, yes.  It isn't easy to do, and it doesn't happen commonly, but it isn't impossible.


There are a variety of known attacks.

One attack involves the attacker pre-mining one or more blocks that spends one or more inputs in a transaction to themselves, keeping that block or chain of blocks to themselves, then broadcasting a transaction that includes one or more of those same inputs in a transaction sent to the victim.  Once the transaction is accepted by the victim, the attacker can release their private chain to the public. As long as their chain is longer than the current chain, the broadcast transaction to the vicitim will cease to exist.

Another attack involves gaining a network connection directly to the wallet that the victim is running.  The attack sends a transaction that pays the victim directly to the victim's wallet.  Meanwhile, the attack simultaneously broadcasts to as much of the rest of the network as they can a separate transaction that spends one or more of the exact same inputs but which pays themselves.  The transaction that most of the network sees is most likely to get confirmed, which will cause the transaction that the victim received to cease to exist.

Another attack involves having enough hashing power to overtake the main blockchain from one or more blocks back.  This will allow the attacker to confirm transactions that spend identical inputs to earlier transactions that they sent in place of the already confirmed transactions that they sent to the victim.

Another attack involves sending a transaction that is unlikely to ever get confirmed (due to extremely low priority and no transaction fee) to the victim.  Then waiting for most peers to drop the transaction from their memory pool.  Then sending a replacement transaction that spends one or more of the same inputs to a different address.

There may be a few more well known attacks, but I think that answers your question.


It rarely happens.  It can happen accidentally if someone sends a transaction that isn't likely to be confirmed.  It can happen intentionally as per the previous descriptions if the attacker has the appropriate skills and resources.


Which process?  Bitcoin's confirmation process is quite secure.  The more confirmations you have, the more secure the transaction is.


Any time blockchain.info sees an input that is used in one transaction, and then later used in a different transaction, they mark it with a double spend warning.  This can be due to orphaned blocks, unconfirmable transactions, or malicious actions.


That depends on what you mean by "sure" and what you consider to be an acceptable level of risk.  You're really getting into some philosophical concepts there.  For example, can I ever be "sure" that anything other than my own consciousness "exists"?


If they just started disappearing when I hadn't done anything at all to my wallet? I'd be concerned, and possibly even in a bit of a panic.

If I had just done something significantly outside the normal use case for the wallet design (such as recovering an entire data directory from the recent past or attempting to re-download the entire blockchain)? I'd assume that I misunderstood the process and I'd calmly make an effort to better understand what I was doing.


Wait for a few confirmations.  Be aware of any significant changes in the rate of new blocks.  Be aware of any significant changes in the block orphan rate.

Dan the man - thankyou

[edit] will suck in this (your) expertise and digest...

Much appreciated for your time to write the reply, it really is.

Great answer to 1), really great answer to 2) - thanks for that.

3) If so, who does it? - and under what circumstances?


Yesterday I got the impression there was some manual intervention (fire fighting) going on. Like someone was noticing a potential double spend attack and manually altering stuff in the chain.
So can the people who control the bitcoin code do it too?

Happy with 4) & 5). Your 6) made me laugh.
7) OK, I suppose restoring a blockchain from a backup may cause an issue locally - but others seen the double spend warning too.

8. How can I (if at all) defend myself from someone performing a double spend attack when sending me coins?  (like the OP topic states)


Ok so nothing for me to do here apart from wait for txns. Got that but I must admit I'm slightly uneasy about it.

Thankyou again

Asking a question is always welcome. It is always good to better understand the bitcoin network rather than blindly believing anyone. Once upon a time I asked a lot of Qs regarding address collision and Danny patiently replied all of them. If u look back to this thread, u'll see I never disqualified your concerns, but the way u reacted to Keyser Soze, is bad. He was trying to explain u... may be u dont like that. But telling it useless is utter insult, which is most unwelcome.


Thank u Danny :)

Keyser Soze - apologies - I must be having a man period...

I'm not sure where you got this impression, but I suspect you are mistaken.  There are no "people who control the bitcoin code".  There is a group of people that control releases of the wallet that is called "Bitcoin Core".  They don't have much more power than that.  Individuals decide for themselves if they want to run that wallet, or if they want to run some other wallet. Other than changing the wallet software and convincing a large number of people to upgrade to their new version of the wallet, there isn't much else that the people that control that software can do.


This is a warning that the blockchain.info website chooses to place on their website when they notice that an input that was received at an address is used in more than one transaction that has been broadcast to the network.  Many times this warning is not due to any malicious attack.


Not txns.  Confirmations.  There's a difference, and using the wrong word is likely to lead to disagreement, misunderstanding, and confusion.

I understand that you're uneasy about it.  It's difficult to trust something that you don't completely understand.  I get nervous every time I get in an airplane, or hear about severe weather headed my way.  It can be even more disconcerting when you understand a few of the basics but don't know much about the important details. Like most things in life, at some point it comes down to a few options:

• Completely avoid the thing that you don't understand, since you can't make an accurate risk assessment without complete understanding of the entire process
• Trust the knowledge of other experts that do completely understand the process.  Rely on their expertise, and keep yourself aware of any new developments and warnings from those that have demonstrated reliable and trustworthy knowledge.
• Become an expert yourself.

I would like to think I can achieve bullet point point 3 in other aspects (I hope) - which seems the best option - and now I will try and achieve it with btc.

Clever man - thanks

Another thing to think about.

We are raised to take certain risks without thinking very much about them.  The risk is so low, and accepting that risk is so much a part of daily life, that we often don't even notice.  Therefore, when we find something new (but similar), we have a tendency to notice the risks in the "new" thing without taking into consideration how much identical risk we are accepting in the "old" thing.

I'm not sure which country you are from, but all countries have their own fiat currency.  All those currencies have similar risks.  Let's use the word "dollar" here, but you can substitute your own currency and government agencies as you see fit...

If you waited for "x" number of confirmations, with "x being a number that would require hashpower whose value exceeds the value of your transaction.

I had made the connection with bitcoin and cash (would you give a stranger your cash - he might run off with it). But I hadn't made the connection with double spends and forged currency (GBP for me btw). Excellent analogy.

Sorry for being off topic. But, I think u have some ready-made notes. Otherwise, it is very unlikely to come up with such an analogy in such a short time span...

I've been discussing the technical details of bitcoin, studying the technical details of bitcoin, educating others about the technical details of bitcoin, thinking about the technical details of bitcoin, and to a certain extent obsessing about the technical details of bitcoin for more than 2 years now.

Many of these conversations have been either partly or completely discussed many times before.

While I have very little in written notes, I've always been pretty good at analytical thinking and have gotten pretty good at using the Google search engine.  I've also got quite a bit of knowledge in my head to draw from.