Flood attack 0.00000001 BC
lachesis:
Quote from: satoshi on August 04, 2010, 04:25:36 PM
Bitcoin isn't currently practical for very small micropayments. Not for things like pay per search or per page view without an aggregating mechanism, not things needing to pay less than 0.01. The dust spam limit is a first try at intentionally trying to prevent overly small micropayments like that.
Bitcoin is practical for smaller transactions than are practical with existing payment methods. Small enough to include what you might call the top of the micropayment range. But it doesn't claim to be practical for arbitrarily small micropayments.
Why isn't it practical? I agree that a good micropayment system would avoid generating thousands of transactions (e.g. one per packet), but that doesn't mean that bytemaster's change idea is wrong:
Quote from: bytemaster
Payments would generally be advanced, say 1 BTC at a time and when the connection closes any "change" would be returned. This rule makes it impossible to pay for a simple "search query" with no further transactions.
That seems like a great use case. Furthermore, as llama said, the fixed component of a transaction fee should always represent the real cost of including that transaction in a block. So, are there any more intelligent and less painful ways of implementing anti-dust spam systems?
bytemaster:
I think the current system works fine. If someone wants to implement a micro-payment system then they will have to host enough nodes and contribute enough processing power to include their small transactions. I see no reason to require any node to accept or forward micro-payment transactions if said nodes does not wish to.
The real issue is that even a simple legitimate automated micro-payment system could overload bitcoin by introducing more transactions than the credit card system currently uses. The net result is that block sizes could become HUGE.
In my use case you have a P2P system where they pay for priority downloads. Assume you have a single "torrent" file with 100,000 people all seeding and downloading. That could easily generate 100,000 micro-payments per minute. Now clearly, the program would only have to use BTC in the event that upload != download between two clients.
It would be distributed and thus there would be no easy way to identify "spam" from legitimate usage. Even using my solution of transferring 1+ BTC at a time and giving change if the balance is greater than 0.01 could cause a transaction bloat writ large.
I suspect that the "cost" of handing individual transactions may be low (.00001 BTC) but the cost of handling ALL of those little transactions from millions of users using automated payment negotiation/bidding systems would quickly make it impossible to even listen for all incoming transactions.
The only solution to this problem is to make broadcasting of a transaction "non free". Namely, if you want me to include it you have to pay me. The net (no pun intended) result is that each client would need to pay other clients to whom they even send their transaction, not just the individual who gets it in a block. In this way the laws of economics take over and no one gets a free ride on the transaction broadcast system.
The implication is that you may not even receive notice of payment until a node that you paid to receive your transaction and *attempt* to integrate it into a block manages to do so. This means that you would not even see 0/unconfirmed and that a transaction must make it into a block before anyone that wasn't paid to *attempt* to integrate it even knows it exists.
This structure would encourage pay-to-ip systems because that make the receiver of the payment responsible for paying to get it integrated. Either they run their own bitcoin generators *or* they pay to send the transaction to someone who is.
satoshi:
Forgot to add the good part about micropayments. While I don't think Bitcoin is practical for smaller micropayments right now, it will eventually be as storage and bandwidth costs continue to fall. If Bitcoin catches on on a big scale, it may already be the case by that time. Another way they can become more practical is if I implement client-only mode and the number of network nodes consolidates into a smaller number of professional server farms. Whatever size micropayments you need will eventually be practical. I think in 5 or 10 years, the bandwidth and storage will seem trivial.
I am not claiming that the network is impervious to DoS attack. I think most P2P networks can be DoS attacked in numerous ways. (On a side note, I read that the record companies would like to DoS all the file sharing networks, but they don't want to break the anti-hacking/anti-abuse laws.)
If we started getting DoS attacked with loads of wasted transactions back and forth, you would need to start paying a 0.01 minimum transaction fee. 0.1.5 actually had an option to set that, but I took it out to reduce confusion. Free transactions are nice and we can keep it that way if people don't abuse them.
That brings up the question: if there was a minimum 0.01 fee for each transaction, should we automatically add the fee if it's just the minimum 0.01? It would be awfully annoying to ask each time. If you have 50.00 and send 10.00, the recipient would get 10.00 and you'd have 39.99 left. I think it should just add it automatically. It's trivial compared to the fees many other types of services add automatically.
Quote from: FreeMoney on August 04, 2010, 07:30:32 PM
Does including more slow down your hashing rate?
No, not at all.
satoshi:
Quote from: bytemaster
Payments would generally be advanced, say 1 BTC at a time and when the connection closes any "change" would be returned. This rule makes it impossible to pay for a simple "search query" with no further transactions.
One alternative is to use a round-up system. You pay for, say, 1000 pages or images or downloads or searches or whatever at a time. When you've used up your 1000 pages, you pay for another 1000 pages. If you only use 1 page, then you have 999 left that you may never use, but it's not a big deal because the cost per 1000 is still small.
Or you could pay per day. The first time you access the site on a given day, you pay for 24 hours of access.
Per 1000 or per day may be easier for consumers to get their heads around too. They worry about per item because it's harder to figure if it might add up too fast. Unlimited for 24 hours they know what the cost will be. Or if 1000 seems like plenty, they're not worrying that it's costing more with each click if they figure 1000 is more than they'll probably use.
17ujzChRb6VPQGyANVyktc1du:
Quote from: lfm on August 05, 2010, 02:52:32 PM
Sending 1 BTC back and forth a million times creates a single transaction chain, sending a million transactions of 0.000001 BTC makes a million nearly independant transactions which all must be remembered. Due to the way bitcoin can drop old deeply confirmed transactions the first is far less overhead than the second in the long run. There may be similar network cost but the disk space cost can be greatly reduced for the single chain.
Only if the "dust" is combined back together and confirmed deeply enough again only then can the dust space be dropped.
Improved attack would be : start with 1BTC then transfer 0.999999999BTC, then 0.999999998BTC, ...
It results 1 million accounts (minus 10000) with 0.000000001BTC each.
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