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The aspect that worries me about this is that links to child pornography websites concealed within transactions could make it theoretically possible for people

The aspect that worries me about this is that links to child pornography websites concealed within transactions could make it theoretically possible for people to share child pornography in a somewhat anonymous way. Given the anonymous nature of the currency it appears it could be used to transmit highly illegal content within the transaction. Although having said that, the same could be said for the Tor network and onion addresses contributing to the same thing. That's the name of the anonymous game, people will do illegal and questionable things that's just the way it will always be. How would these injectable pieces of data be removed from transactions without exposing transactions to attacks?

epscylonb 14y ago
You can't put arbitrary data in a transaction, at least not very easily. The bitcoin devs are pretty clear that the bitcoin network and blockchain should not be used for messaging or store non transaction related data. What actually is happening here, is that miners have the opportunity to put a small amount of arbitrary data in a block when they mine. Ideally this is should be random data, its purpose is to change the data being hashed so you get a different hash each time you try. In my view the author of bitcoin set a bad precedent by including a newspaper headline referring to bank bailouts in the very first block. However I can't begrudge him for that too much. Since 2009, people have included prayers and accusations of illegal activity (trolling) in blocks. Assuming increased bitcoin adoption, I see mining getting more and more centralized, already I don't think any of the major mining pools would be silly enough to include CP or other illegal content. It would take many blocks to store a non trivial sized image in the blockchain, and if they put a link in instead then of course the host could be taken down.
- rlpb 14y ago
  > You can't put arbitrary data in a transaction, at least not very easily. No; it's very easy. Anyone sending Bitcoin can add arbitrary data in his transaction; no need to be a miner: https://en.bitcoin.it/wiki/Script#Transaction_with_a_message https://en.bitcoin.it/wiki/Script#Transaction_with_a_message
- eric_bullington 14y ago
  Satoshi included a headline in the blockchain to serve as a timestamp to prove that mining had only started at the time of his public announcement about the project. However, the particular headline chosen as a timestamp was probably not selected at random.
limmeau 14y ago
The Bitcoin community could agree on one block to be the "last" block and compute all balances reached so far. Then start a new block chain with a special first block which initializes the balances. This requires a protocol change and lots of coordination, but may be preferable to a situation where mere possession of a copy of the block chain qualifies you for jail.
- rmc 14y ago
  You'd have to change the code to prevent adding arbitary data aswell, otherwise someone will just re-add stuff.
Samuel_Michon 14y ago
“the anonymous nature of the [Bitcoin] currency” Could you elaborate on that? I thought Bitcoin was less anonymous than say, cash money. Unless you mine the Bitcoins yourself (which is getting harder every day) you would have to buy them somewhere or get someone to give them to you, right?
- sp332 14y ago
  Bitcoins are somewhat traceable. But if you're not spending them, and just want to inject some bitcoin transactions into the network, there won't really be any link to a person. The main thing you'd have to be careful of is not to send the transactions from the same wallet you normally use to buy things.
diggan 14y ago
You should read about the Tor Project[1] where there is easy to share things like child pornography and other stuff fully anonymous. If you browse to a index site like The Hidden Wiki, you'll see that it already exist ways for people to share exactly what they want, even illegal stuff. [1] https://www.torproject.org https://www.torproject.org

epscylonb 14y ago

You can't put arbitrary data in a transaction, at least not very easily. The bitcoin devs are pretty clear that the bitcoin network and blockchain should not be used for messaging or store non transaction related data. What actually is happening here, is that miners have the opportunity to put a small amount of arbitrary data in a block when they mine. Ideally this is should be random data, its purpose is to change the data being hashed so you get a different hash each time you try. In my view the author of bitcoin set a bad precedent by including a newspaper headline referring to bank bailouts in the very first block. However I can't begrudge him for that too much. Since 2009, people have included prayers and accusations of illegal activity (trolling) in blocks. Assuming increased bitcoin adoption, I see mining getting more and more centralized, already I don't think any of the major mining pools would be silly enough to include CP or other illegal content. It would take many blocks to store a non trivial sized image in the blockchain, and if they put a link in instead then of course the host could be taken down.

rlpb 14y ago
> You can't put arbitrary data in a transaction, at least not very easily. No; it's very easy. Anyone sending Bitcoin can add arbitrary data in his transaction; no need to be a miner: https://en.bitcoin.it/wiki/Script#Transaction_with_a_message https://en.bitcoin.it/wiki/Script#Transaction_with_a_message
eric_bullington 14y ago
Satoshi included a headline in the blockchain to serve as a timestamp to prove that mining had only started at the time of his public announcement about the project. However, the particular headline chosen as a timestamp was probably not selected at random.

limmeau 14y ago

The Bitcoin community could agree on one block to be the "last" block and compute all balances reached so far. Then start a new block chain with a special first block which initializes the balances. This requires a protocol change and lots of coordination, but may be preferable to a situation where mere possession of a copy of the block chain qualifies you for jail.

rmc 14y ago
You'd have to change the code to prevent adding arbitary data aswell, otherwise someone will just re-add stuff.

Samuel_Michon 14y ago

“the anonymous nature of the [Bitcoin] currency” Could you elaborate on that? I thought Bitcoin was less anonymous than say, cash money. Unless you mine the Bitcoins yourself (which is getting harder every day) you would have to buy them somewhere or get someone to give them to you, right?

sp332 14y ago
Bitcoins are somewhat traceable. But if you're not spending them, and just want to inject some bitcoin transactions into the network, there won't really be any link to a person. The main thing you'd have to be careful of is not to send the transactions from the same wallet you normally use to buy things.

diggan 14y ago

You should read about the Tor Project[1] where there is easy to share things like child pornography and other stuff fully anonymous. If you browse to a index site like The Hidden Wiki, you'll see that it already exist ways for people to share exactly what they want, even illegal stuff. [1] https://www.torproject.org https://www.torproject.org