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Author Topic: Bitcoin in danger!? Received <Sent!?!  (Read 4443 times)
Night
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February 10, 2012, 12:32:47 AM
 #1

Bitcoin test-net
See  http://blockexplorer.com/testnet/address/mtoKs9V381UAhUia3d7Vb9GNak8Qvmcsme
Received BTC: 152.7792
Sent BTC: 202.7792
50BTC sent to more than got it!?!?
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February 10, 2012, 12:36:30 AM
 #2

Doesn't that mean you gave it to the miner?

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February 10, 2012, 12:41:27 AM
 #3

before anyone misunderstands ... this is on testnet and not the bitcoin blockchain
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February 10, 2012, 12:46:39 AM
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lol Cheesy

It is pitch black. You are likely to be eaten by a grue.

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February 10, 2012, 12:47:24 AM
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What is the difference of the Bitcoin and  Bitcoin TestNet? Technically, nothing! So it can happen in Bitcoin
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February 10, 2012, 01:08:29 AM
 #6

Bitcoin test-net
See  http://blockexplorer.com/testnet/address/mtoKs9V381UAhUia3d7Vb9GNak8Qvmcsme
Received BTC: 152.7792
Sent BTC: 202.7792
50BTC sent to more than got it!?!?
50 BTC block reward. 

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February 10, 2012, 01:28:51 AM
 #7

Are they testing out a new BIP? This could be due to a bug in a BIP someone is trying to implement and why I am an advocate of an excessive level of testing on testnet before it ever makes it to the real bitcoind.
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February 10, 2012, 01:31:59 AM
 #8

negative balance.. oh dear

(BFL)^2 < 0
koin
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February 10, 2012, 01:42:13 AM
 #9

bip -1
to compete with the banking system, bitcoin now supports overdrafts.   any overdraft will cost you in fees enough to pad a new bonus system to overly compensate the bitcoin executives at the top.

seriously though ..., this is a problem somewhere, right?  (but is isolated to whatever code blockexplorer is using for testnet only, right?)
Gavin Andresen
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February 10, 2012, 02:27:33 AM
 #10

Don't panic.

roconnor has been experimenting with spending "duplicate coinbase transactions" on the testnet.  Block explorer is confused, and isn't seeing the 50 bitcoins generated to that address in testnet block 45,442 (because the generation transaction has the same ID as the generation transaction in block 45,333).

Expect code changes before the 0.6 release is final to discourage and eventually prohibit accepting blocks with duplicate coinbase transactions; although we can't see a way to exploit this weirdness to cheat anybody (it is easy to cheat yourself out of bitcoins using duplicate coinbase transactions that cannot be spent), it's definitely not a good thing.

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February 10, 2012, 02:59:03 AM
 #11

No worries.

theymos
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February 10, 2012, 02:59:47 AM
 #12

Notice that tx 0018417e23... and fae8bfd6a2... on that address ledger spend the exact same output. It looks like a double-spend, but it's actually a less severe bug in the protocol that probably doesn't allow for any easy attacks. (Because the bug causes very strange behavior, though, it might allow for attacks that have not been thought of yet.)

These transactions actually broke Bitcoin Block Explorer when they first appeared because there was a database constraint preventing double-spends from being inserted into the database. I "fixed" it by removing the constraint, but this causes BBE to display these transactions strangely. A lot of code would need to be changed, but I might fix it fully some day.

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February 10, 2012, 03:04:12 AM
 #13

Good job Gavin!! Testnet is... FOR TEST!!!   Wink

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February 10, 2012, 03:56:49 AM
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Notice that tx 0018417e23... and fae8bfd6a2... on that address ledger spend the exact same output. It looks like a double-spend, but it's actually a less severe bug in the protocol that probably doesn't allow for any easy attacks. (Because the bug causes very strange behavior, though, it might allow for attacks that have not been thought of yet.)

That sounds pretty terrible. Shocked

(BFL)^2 < 0
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February 10, 2012, 04:49:02 AM
 #15

Technical explanation:

When you create a block, the coinbase transaction which generates 50 BTC can easily be made to exactly equal a past coinbase transaction: it just needs to pay out to the same address and have the same (arbitrary) scriptSig. Unfortunately, this transaction will then have the exact same hash as another transaction in the chain. Satoshi did not anticipate this, so it's allowed by the protocol and it confuses the Bitcoin code.

In this case, roconnor:
- Generated a block containing a normal coinbase transaction.
- Spend the BTC generated in the coinbase transaction. Bitcoin nodes mark the coinbase transaction's output as spent.
- Created a block containing a duplicate of the first coinbase transaction. Bitcoin nodes will now overwrite the first coinbase transaction in the transaction database. The output of the coinbase transaction is marked as unspent. The transaction spending the original coinbase output is not affected and is still considered valid.
- Spent the BTC generated in the second coinbase. There are now two transactions spending the "same" output.

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February 10, 2012, 05:05:48 AM
 #16

Technical explanation:

When you create a block, the coinbase transaction which generates 50 BTC can easily be made to exactly equal a past coinbase transaction: it just needs to pay out to the same address and have the same (arbitrary) scriptSig. Unfortunately, this transaction will then have the exact same hash as another transaction in the chain. Satoshi did not anticipate this, so it's allowed by the protocol and it confuses the Bitcoin code.

In this case, roconnor:
- Generated a block containing a normal coinbase transaction.
- Spend the BTC generated in the coinbase transaction. Bitcoin nodes mark the coinbase transaction's output as spent.
- Created a block containing a duplicate of the first coinbase transaction. Bitcoin nodes will now overwrite the first coinbase transaction in the transaction database. The output of the coinbase transaction is marked as unspent. The transaction spending the original coinbase output is not affected and is still considered valid.
- Spent the BTC generated in the second coinbase. There are now two transactions spending the "same" output.

Do you lose the original if it isn't spent when you make the new identical one? Because when you spend either now it'll be marked as spent?

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theymos
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February 10, 2012, 05:12:11 AM
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Do you lose the original if it isn't spent when you make the new identical one? Because when you spend either now it'll be marked as spent?

Right. This has happened a few times on the main network, actually. Not sure if anyone realized until recently that it was possible to spend both, though.

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February 10, 2012, 05:20:43 AM
 #18

Do you lose the original if it isn't spent when you make the new identical one? Because when you spend either now it'll be marked as spent?

Right. This has happened a few times on the main network, actually. Not sure if anyone realized until recently that it was possible to spend both, though.


Shocked

Anyway, now this guys will solve a bug!

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February 10, 2012, 05:35:32 AM
 #19

so to clarify, the main consequence of the bug was that a block reward could become lost forever?

still... turning 100 BTC into 50 is less serious of a bug than being able to turn 50 BTC into 100 Cheesy
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February 10, 2012, 05:41:34 AM
 #20

so to clarify, the main consequence of the bug was that a block reward could become lost forever?

still... turning 100 BTC into 50 is less serious of a bug than being able to turn 50 BTC into 100 Cheesy


Well, I think that ANY overwrite is serious...

But you got a point!

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