
How porn links and Ben Bernanke snuck into Bitcoin's code - T-A
http://money.cnn.com/2013/05/02/technology/security/bitcoin-porn/index.html
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pyre
When you attempt to make something that "no one can control," then things like
this happen. Same thing with child porn on Tor .onion addresses.

I'm curious what the implications of making some of these removable from the
block chain though. Would it just end up being some central authority deciding
which transactions are 'appropriate?' Is there a deterministic way of
filtering out these 'data spam' transactions (without side-effects)?

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ZeroCoin
re: "is there a deterministic way[?]"

I would assume so.

Perhaps adding a word-checker to bitcoin clients that looks for recognizable
words (or attempts to validate a URL found inside the most recent block).

If block contains words or URLs, disregard it. If not, accept it.

Now Namecoin on the other hand...

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tlrobinson
If I understand correctly, these people are using special software to encode
data in transactions, namely the output addresses. You can only embed
arbitrary data in blocks if you're able to mine a block (like Satoshi's
headline in the genesis block and Dan Kaminsky's Ben Bernake ASCII art),
otherwise you need to encode it in the transaction data.

~~~
ZeroCoin
Well then all of the worries about this child-porn being in the blockchain are
warrantless.

You could create a link to child-porn from this very comment I just posted
using the right cipher. I am sure of it.

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gizmo686
What if A) your comment was preserved as a part of the block-chain that could
not be removed without doing serious damage to bitcoin. And B) the cipher you
are using is a publicly known cipher recognized as the standard way of
encoding data into the block-chain.

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unimpressive
Wait, HN is now a source of comments for _CNN_? That's worrying.

~~~
gwern
I dunno, I think I'd trust random HNers for accuracy in their technical
commentary more than I would CNN.

(This is more criticism of CNN than praise of HN, understand.)

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lostlogin
I don't know about that. With care there is a hell of a lot to be learnt here
and at least the crap gets down voted, where news site promote popular
stories. Link bait versus quality comments and voting.

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DigitalSea
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
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
> 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>

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smrtinsert
I was surprised when I didn't see this on HN first. I wonder what would happen
if an organization like wikileaks began injecting documents into the
blockchain.

~~~
nwh
There's already a 7z binary of wikileaks crap in there. About 3MB of the
stuff.

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junto
If I understand this correctly, the blockchain transaction file is already
pretty big (i.e. a couple of GBs). When you first setup Bitcoin on your
machine you are basically required to download this file, and it is then kept
up to date using Bittorrent, presumably with partial updates?

I believe that there is a way (within the bitcoin design), such that the file
size can be limited, firstly by only downloading the transaction headers, and
/ or secondly, by removing historical transactions (by breaking off branches
from the Merkle tree
[[http://bitcoin.stackexchange.com/questions/10333/blockchain-...](http://bitcoin.stackexchange.com/questions/10333/blockchain-
long-run-issue\])).

However, when do those measures come into play? Do they have to be switched
on? If so how, the whole thing is decentralized? Are the full transaction
histories already being pruned?

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skriticos2
The header only download is a client side thing and can be done already (with
a client that supports it). The Unused Output Tree (UOT) - the second thing
you mentioned - needs amendment to the blockchain (adding checkpoints).

[https://en.bitcoin.it/wiki/Thin_Client_Security#Header-
Only_...](https://en.bitcoin.it/wiki/Thin_Client_Security#Header-Only_Clients)

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wyck
There is dirty money and then there is _dirty_ _dirty_ money.

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camus
but how to tell the difference ? lol

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ZeroCoin
Come on guys, this is HN. Not Reddit.

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asveikau
Face it, all web communities eventually evolve into YouTube comments.

~~~
lucian1900
Although, especially recently, YouTube comments have gotten much better.

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bitcoinctf
If you know a bit about web security (think Stripe CTF 2.0) and would like
Bitcoins to try this, you can visit <http://bitcoinctf.com>

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rmc
This could get very _"interesting"_ if people started building a communication
system on top of BitCoin. It could get bitcoin shut down....

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joshschreuder
It would be interesting to see a tool that searched the blockchain extracting
possible plaintext decodings.

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charlejshort
Short sell bitcoin; then insert base-64 encoded child porn. (or perhaps salt
multiple transaction and then leak decode process of higher res image) _bling_
criminal mastermind or future jailhouse bitch...

