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    Author Topic: Untaint for a fee using out-of-band transactions and large mining fees  (Read 1358 times)
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    Peter R (OP)
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    March 04, 2014, 07:39:12 AM
     #1

    Although I very much doubt the dystopian future envisioned by a few here.  You know, the future where coin tainting authorities blacklist coins of people they don't like and the coin police confiscate coins from honest users just because they may have been used to buy illicit goods 14 transactions back.  I think that is tinfoil-hat talk.  I believe most people want a free and fair system, and so bitcoin will stay free and fair.

    But I thought of a way to untaint any coin today and I wanted to share it in case it hasn't been discussed (although I'm sure it has).  

    When a new block is found, the miner is permitted to reward himself with a coinbase transaction equal to the block reward (currently 25 BTC) plus the sum of all transaction fees included in the block.  In a certain sense then, these newly generated coins come pre-tainted: a bit of taint was peeled off every fee-paying transaction included in the block.  So each newly generated coin can be traced back to a lot of addresses.

    It's not very useful to define taint in this way, so blockchain.info for instance does not include it.  If you perform taint analysis on a newly generated coin, you'll find zero taint.  

    But what this means is that you could untaint any coin if you knew a willing and trustworthy miner.    Let's say you control the private key to an address that contains 10 BTC that you wish to untaint.  You'd create a transaction that takes as inputs these 10 BTC and outputs something like 1 mBTC.  You basically give everything away (9.999 BTC) as a miner's fee.  

    You can't broadcast this transaction publicly on the network, as you'd certainly lose your coins.  Instead, you'd send this transaction over a private back-channel to a miner offering the untainting service.  When the miner finds a block, your 9.999 BTC gets added to his coinbase transaction.  The miner deducts a few percent for the service, and sends you back your coins, completely untainted.  

    Of course, a tainting authority could become more sophisticated and trace taint through coinbase transactions too, but this quickly becomes unmanageable I think for reasons that I won't get into as this post is already long enough...



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