Unknown transaction - very interesting [SOLVED]

[btcxyzzz]

Yesterday, I received 0.00000002 BTC in my wallet. I don't know who sent that. Transaction id is: 02341dbe4198915f807be0a0720d0a4ac37ca4b50bb2e957c49f400a21e7c65f-000, but what's most interesting is that I can't find that transaction at blockchain.info, it does say "Firstbits not found", so it's all a complete mistery for me... Somebody care to explain?

Thanks...

[flatfly]

Yesterday, I received 0.00000002 BTC in my wallet. I don't know who sent that. Transaction id is: 02341dbe4198915f807be0a0720d0a4ac37ca4b50bb2e957c49f400a21e7c65f-000, but what's most interesting is that I can't find that transaction at blockchain.info, it does say "Firstbits not found", so it's all a complete mistery for me... Somebody care to explain?

Thanks...

It is on blockchain.info - just remove the "-000" at the end.

[btcxyzzz]

Thanks..... So it's whole new way of spamming people. Given the fact it's kind not annoying (because finally you get some bucks , I can say it's even ethical way of pushing ads.

[Zebra]

For that tx, the sender sent a few satoshi to 53 different addresses (+1 for the change) and paid 0.0002 tx fee.

Out of curiosity, receivers will search blockchain.info and see the ad.
If the sender is lucky, someone would make a post in bitcointalk or reddit, and then more people will see the ad.

[Cryddit]

It has another aspect though; it is an attack on privacy.

Next time you pay someone bitcoin, that 2 Satoshi or whatever will be listed as a separate input along with it.  This enables someone watching the blockchain to identify additional coins in the transaction as belonging, as of the time of that transaction, to the same person who "accepted" the 2 Satoshi. 

So, if a mobster wants to know what someone is spending money on, he can send 2 Satoshi to any address he *knows* that person controls, and then watch to see where that 2 Satoshi gets spent - learning, at the same time, many *additional* coins his competitor controlled as of that time, that he wouldn't know about if he didn't know to watch this 2 Satoshi. 

Because the coin selection algorithm is predictable, the 'gift' can be precisely timed to ensure that the 2-Satoshi coin is included in a particular transaction that the attacker knows will be happening at some predictable time - such as, say, the Police Department distributing paychecks to undercover detectives.  And should coin resulting from *that* transaction later be spent, with no intervening tx, by one of his employees, that employee should hope his life insurance is paid up.

I believe that there ought to be a privacy-consciousness setting in the client; if you switch it on, it rejects dust payments by immediately spending them in a tx with no outputs (ie, gifting them to the miner who gets the block).

[gmaxwell]

I believe that there ought to be a privacy-consciousness setting in the client; if you switch it on, it rejects dust payments by immediately spending them in a tx with no outputs (ie, gifting them to the miner who gets the block).

There is a tool to do basically this, but even better: it ships them off to a server where they are coinjoined up in a single transaction, thus confusing simplistic taint analysis.

https://github.com/petertodd/dust-b-gone/

Everyone with dust in their wallet should use it— even if you don't care about your own privacy, giving up your dust inputs is good for the network and improves other people's privacy.

Because the coin selection algorithm is predictable,

The algorithm is randomized and I'm not aware of any way to easily control when a coin gets used except by making it exactly the right unusual value.

E.g. you send the person 1.123456  and then get them to pay 1.123456 and it is very likely that they'll use the intended coin, though in that case there wouldn't be any other inputs.

Not that privacy attacks with dust aren't a concern, but it's isn't quite as trivial as being able to control when the coins are used directly.