Someone could buy or mine bitcoins, and send them in small transactions all day to spam the blockchain.

Is this possible? And could this mean the end of the trust people have in bitcoin?

edit:

And what if someone makes bigger than 0.01 BTC transactions from one of his address to another all day. Making thousands of meaningless transactions, those totally spamming the blockchain. That wouldn't even cost much I believe. Is this possible?

up vote 7 down vote accepted

Such transactions will be subject to fees. You can read about the fee schedule here. The fees apply if the transactions send a small amount of coins, or send the same coins over and over (giving the transactions a low priority score).

The fee is set at BTC 0.0001 per 1000 bytes. Thus someone who wants to spam the block chain with 10 MB will have to pay at least BTC 1 in fees. That's about US$500 at today's prices, and it causes the block chain to increase in size by about 0.1%, which nobody will probably even notice. If you're going to spend $500 on mischief, you'll get a lot more bang for the buck by spending it on eggs and toilet paper!

  • So basically the network knows if I'm sending that 0.1 BTC between my 2 addresses all day, and deprioritizes it? – Barna Kovacs Nov 20 '13 at 17:34
  • @Rails: Right. Specifically, it looks for the age of the transaction outputs that are being spent. If you are transferring coins that were previously transfered a short time before, the priority goes down, and you have to pay a fee to get the transaction recorded. – Nate Eldredge Nov 20 '13 at 18:00
  • who gets the fee? – SuperUberDuper Aug 26 '16 at 17:03
  • @SuperUberDuper: It goes to the miner who includes that transaction in a block. bitcoin.stackexchange.com/questions/9895/… – Nate Eldredge Aug 26 '16 at 18:08
  • ok thanks!!!!!!! – SuperUberDuper Aug 27 '16 at 18:59

Yes, it is possible, and called transaction spamming. If you consider it cost effective spamming probably depends on how much it is worth to you to bloat the blockchain, already at a size measured in double-digit GBs, for everybody who keeps a complete copy!

However, there are some possible mitigations already implemented. First of all, many clients delay forwarding very small transactions and delay incorporating them into blocks or even require a transaction fee for them. As the transaction spam problem becomes larger, surely more mining pools will stop bothering unless a transaction fee is included.

Finally it is not strictly necessary for every single client to keep every single block of the blockchain around. Hence the long-term impact of such spamming is probably rather limited, and its widespread implementation, if not now then at least sooner or later, costly.

You can create unlimited addresses and then send amounts of bitcoins which are over the fee-less minimum transaction limit to your own addresses. That means you can technically spam the blockchain for the price of the electricity.

A transaction may be safely sent without fees if these conditions are met:

  • It is smaller than 1,000 bytes.
  • All outputs are 0.01 BTC or larger.
  • Its priority is large enough (see the Technical Info section below)

https://en.bitcoin.it/wiki/Transaction_fees

Anyone know how the bitcoin core could stop you from doing that without blocking your IP from the network?? Even in that case, all you need to do is spoof your IP address over and over again>>>

There was similar thread of someone sending the smallest amount of bitcoin (probably for spamming puposes) here. However I put on my blog a bitcoin address and so far have recieved any smallest amount. Bitcoin price is pretty high so sending smallest ammout (0.00000001) wouldn't be cost effective spamming.

  • And what if someone makes bigger than 0.01 BTC transactions from one of his address to another all day. Making thousands of meaningless transactions, those totally spamming the blockchain. That wouldn't even cost much I believe. Is this possible? – Barna Kovacs Nov 20 '13 at 11:16

Every transaction has to be confirmed and fees are required, miners rely on them. This has been discussed on bitcointalk and very nice explanation is here. Also you can check bitcoinfees.com for informations related too a transaction fee.

It's possible, but Bitcoin was designed to have humans filtering transactions for just this reason. Miners have the responsibility to keep the blockchain free of spam, and nodes can help filter it at the network/relay level. Often this is done by only relaying/mining transactions that have certain properties (ie, obviously aren't likely to be spam because they move a high volume of old coins) or transaction fees (so that spamming is expensive). Some spammers exploit human weakness and trick gamblers into paying fees for them, so some miners employ more advanced spam filters to try to identify these as well.

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