If I had such scheme in my client I'd use it to see if I received some coins from that famous pizzas (numismatic value).

And, since the possibility is already there, yes, out of curiosity, I'd keep track of the famous heists too.

I'd keep track of how old my coins really are, if they are freshly mined etc.

Don't need a fork to do this.

The true is that bitcoins are not fungible like metals (Jules Rimet Trophy melted down by thieves in Rio de Janeiro - 1983), and it's easier to track than cash.

Can someone explain how they'd fork the blockchain?

For all you know, half the people you've traded with in the last month already have a special client with a blacklist/whitelist in it.  How would you identify them so that your client doesn't let them back on the "taint-free" fork of the blockchain?  I think you might have a good answer to this, but it will be one which demonstrates a misunderstanding of the original proposal.

I've received at least one personal request to continue developing this idea from someone who suggested that the information in the blockchain will probably be an important part of the future of private justice.  That is, in fact, why I came up with the idea.

No one has yet pointed out explicitly that if a thief were on this discussion, that thief would make every effort to discourage people from even thinking about the proposal.


This is an interesting perspective.  I only meant that anyone, regardless how they feel about fungibility, can compile a list of all the address that currently hold coin that was in an address that contained allegedly stolen bitcoins.  So perhaps "taint" is the wrong word for westky to use in describing this fact.

To confuse the issue even more, I have developed a theory (silly, if you want to call it that) that the reason no reward has been offered by the victims of heists is that they weren't really victims:

• A large dealer creates a hidden (fake) member
• The fake member "steals" bitcoin
• The dealer "loses" all the records indicating who they owe.
• The dealer announces that they will reimburse all customers who can prove their claim
• Less than 100% of the customers prove their claims
• The dealer reimburses claims using the stolen bitcoin (after mixing it up enough to avoid suspicion)
• The dealer ends up with some stolen coin that didn't get reimbursed to customers who failed or didn't bother to prove a claim - customers who have abandon bitcoin because it's too insecure.

Anyone can do that if they have the marketing power and the lack of morals.  But they're in danger if we start analyzing the blockchain more closely.

Given the vehemence of the responses to the proposal, I've become ambivalent on the likelihood of this theory.  I asked Gavin for advice in setting up Python so I could enhance his BitcoinTools to do this backtracing, but he hasn't answered.  So, large dealers who are unethical thieves, you might want to pressure him into ignoring me, and perhaps removing the tools lest some other curious soul use them to demonstrate that my theory is true.  I sure hope to hell it isn't.

Bitcoin is a protocol.  The Bitcoin.org client is code that implements the Bitcoin protocol.  This taint blacklist idea of yours could be implemented in a client without touching the Bitcoin protocol or requiring a hard-fork to the blockchain.    So my reference earlier to a fork was describing alterations to the Bitcoin.org client and not to a fork of the blockchain.   As you also mentioned, you could even implement a taint blacklist that does not require changes to the Bitcoin.org client (e.g., this could easily be done in Armory, for instance, or some other external service.)

So, it's technically very possible for you to do this.  Go do it.  What are you waiting for?  Go nuts!

The reason you haven't is because you know that unless others are using that taint blacklist as well, you doing so unilaterally has no effect.   If you'ld like to boycott tainted coins, you don't need anyone's permission.  You are free to do so.   Isn't Bitcoin and open source fantastic, where you have the liberty to take the software and to basically be allowed to do pretty much whatever you want to with it?

Now if instead you want to change the software that I use, that's when I start to have a problem with you.  Your freedom ends where my nose begins.

Some people are thick that way.. 

You don't have to accept coins that have been obtained dishonestly, either. That would be a personal choice. Because bad actors could respond, to honest traders who only making transactions with other honest people, with violence does not invalidate the idea.


What you're asking is like asking how Mt. Gox can give you 5 USD/BTC one day and 6 USD/BTC the next day. Why are exchange rates set on an open market with bids and asks any different than devaluing dishonest money? If someone you want to trade with wants to charge you more because you have dishonest money, you don't have to trade with them. I'd encourage you to find someone to trade with that will give you the full value you believe your BTC is worth.

Tainting won't make it less profitable for theives. Just like copy protection, the tainting will only make things difficult for the honest users. Thieves will just work around any tainting you propose.

By the same local authorities which enforce all businesses to be registered and pay their taxes etc.
Bitcoin exchanges and popular high-transaction merchants can be required to implement taint-aware systems by whatever geographical jurisdiction they operate in.

No - the mixing matters not. It's computationally intensive, but nevertheless practical with today's technology to follow the chain and apply taint in the appropriate percentages.


Nice.. but you seem to still be missing the point.
The various 'taint lists' are overlays that will be applied in multiple (usually geographic) jurisdictions. You will always be free to trade Bitcoins as if the taint lists don't exist with other like-minded taint-haters (or because particular taints are largely only enforced in a region you are unlikely to deal with). This isn't about changing the protocol, nor even the reference client.

The effect of various taint-lists being applied is that there will be a viral incentive for the average user to subscribe to them in order to maximize their wealth.
(In terms of being able to freely spend their coins at the various government-audited exchanges & merchants)
Now it's perfectly reasonable to argue that if someone advertises a price in 'BTC' - that this should imply *any* BTC ie a taint-agnostic transaction. I wholeheartedly support that sort of up-front honesty in the arrangement of any Bitcoin deal.



Of course. This much should be obvious by now.  
Subscribing to any (of the presumably multitudinous) taint-lists is completely optional - except that there is a clear viral pressure on the average consumer to opt into using taint-aware wallet software in order to avoid
a) penalty-taxes at control points
b) mandatory government reporting on your recent transactions if you happen to be 'early' in the chain of transactions since a particularly attention-worthy event.
(e.g kidnap proceeds, terrorism funding etc)



No. Have you?  Are you being facetious here?
Perhaps you don't understand the point that taints can (I predict 'will') be applied if Bitcoin ever becomes seriously mainstream across the globe.

You'll always be free to laugh at the small nation on the other side of the world which implements this, and offer their citizens fewer 'clean' bitcoins from your stash in exchange for Bitcoins that those silly folk view as 'tainted'.   Profit for you! 
(At least until some sort of international cooperation amongst tainting authorities starts to make some of your coins spendable without penalty at fewer merchants)

The only way this sort of system won't work is
a) If some sort of 'blinding' mechanism gets built into the Bitcoin protocol
(see: https://bt.irlbtc.com/view/82947.0   I don't know enough about this to know if it's feasible though)

b) The various taint-implementing authorities go overboard in applying taint - thus so expanding the pool of 'tainted' coins that the black-market economy is effectively stimulated.  (see my earlier comments about it being somewhat self-limiting in this regards)

c) political/social pressure makes tainting impractical for authorities to implement.  
I think this is a fools hope in that some authorities somewhere will implement it anyway. If you can manage to get the law in your country to declare it unconstitutional or unreasonable in some way to 'tax' people via this sort of system - good on you.. but when balanced against law-enforcement's mandate to curtail kidnapping, terrorism etc... good luck!


My preference would lean towards a) but with provisos.
I think your dismissal of the possibility of this sort of viral-tainting even occurring is damaging to the possible consensus required to avoid it in some technical manner.
A counter-argument to implementing a) would be that if law-enforcement truly can't curtail things such as assassination markets and other 'worst of the worst' events, then their only alternative is to crack down in the most draconian ways imaginable to declare Bitcoin utterly illegal and thus limit it forever to the black market.
I suspect that it would be preferable to live with the various self-limiting taint systems and allow Bitcoin to expand to more mainstream usage.

I've not seen anyone else comment on my notion that any authority which over-tainted would effectively be acting against their own interests by increasing the incentive to spend their coins on black-market goods and services.  If this is the case, and I think it is, then a world in which various taints are enforced is preferable to a world in which Bitcoin is equated with terrorism and treated in a zero-tolerance manner by authorities.

Taint systems or not - you'll always be free to transact Bitcoins with others who value them irrespective of taint.
With taint-systems - Bitcoin has a chance of serving more than the black market niche.

It was hard enough to take this thread seriously before the name change...