<ol>
<li><p>The current maximum size of a block is 1 MB.  Current block sizes are about half that, so the absolute worse case scenario is that the block chain grows in size twice as fast as it does now.  That's not particularly scary.</p></li>
<li><p>It's easy to create more than 1 MB of transactions every 10 minutes.  If anyone does that, some transactions can't be included in blocks.  However, at present, there are almost always more transactions available than miners are willing to include in blocks, so we're already at the point where miners need to choose what transactions get included.  </p>

<p>For the most part, miners choose based on fee per kilobyte of transaction data, so transactions that pay more fee/kB get included in blocks sooner.  If someone wanted to, they could create large transactions that paid large fees in order to raise the transaction fee the rest of us would need to pay.  Since that would cost the attacker money every block without actually preventing us from using the system (if we were willing to pay the higher fees), it's also not particularly scary.</p></li>
</ol>

CC BY-SA 3.0
2014-12-22T23:34:46.177Z
And what if transaction fees are kept to a minimum? I understand the topic starter's worry of spamming the blockchain.
gosuto
CC BY-SA 3.0
2014-12-23T02:27:26.913Z
@jorijnsmit I think the answer above already answers that.  If all miners create max-sized blocks, the most spam can do is grow the block chain about twice as fast.  If the spammer pays very low fees, real block chain users like you and me can continue paying regular fees to get pretty much exactly the same quality of service we get now.  Spam is bad, no doubt, but its potential for damage within Bitcoin is currently well bounded.
David A. Harding
CC BY-SA 3.0
2014-12-20T23:34:44.290Z
2014-12-20T23:34:44.290Z
David A. Harding
<p>What if some government start using their computers to move the tiniest amount of Bitcoin possible, from wallet to wallet, just to make the blockchain REALLY big? Is this possible?</p>

<p>And also, is it possible to generate large amounts of transactions so that one winning node can't include them all in one 10 minute mining process? </p>

CC BY-SA 3.0
2014-12-25T01:37:51.617Z
You don't need the govt. 8 of the top 10 most popular addresses are for SatoshiDice and similar.
Wizard Of Ozzie
<blockchain><attack><blocksize><transaction-selection><spam>
What if some group of people start sending small transactions from wallet to wallet just to make the blockchain bigger?
Guelando 2
# What if some group of people start sending small transactions from wallet to wallet just to make the blockchain bigger?

(Asked by: username_0 on 2014-12-20)

What if some government start using their computers to move the tiniest amount of Bitcoin possible, from wallet to wallet, just to make the blockchain REALLY big? Is this possible?

And also, is it possible to generate large amounts of transactions so that one winning node can't include them all in one 10 minute mining process?

**Tags:** blockchain, attack, blocksize, transaction-selection, spam

> **Comments:**
> **username_1**: You don't need the govt. 8 of the top 10 most popular addresses are for SatoshiDice and similar.  

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## 1 answers

### Answer by username_2 on 2014-12-20. Score: 9 | Accepted answer

1. The current maximum size of a block is 1 MB. Current block sizes are about half that, so the absolute worse case scenario is that the block chain grows in size twice as fast as it does now. That's not particularly scary.
2. It's easy to create more than 1 MB of transactions every 10 minutes. If anyone does that, some transactions can't be included in blocks. However, at present, there are almost always more transactions available than miners are willing to include in blocks, so we're already at the point where miners need to choose what transactions get included.

   For the most part, miners choose based on fee per kilobyte of transaction data, so transactions that pay more fee/kB get included in blocks sooner. If someone wanted to, they could create large transactions that paid large fees in order to raise the transaction fee the rest of us would need to pay. Since that would cost the attacker money every block without actually preventing us from using the system (if we were willing to pay the higher fees), it's also not particularly scary.

> **Comments:**
> **username_3**: And what if transaction fees are kept to a minimum? I understand the topic starter's worry of spamming the blockchain.  
> **username_2**: @jorijnsmit I think the answer above already answers that.  If all miners create max-sized blocks, the most spam can do is grow the block chain about twice as fast.  If the spammer pays very low fees, real block chain users like you and me can continue paying regular fees to get pretty much exactly the same quality of service we get now.  Spam is bad, no doubt, but its potential for damage within Bitcoin is currently well bounded.  

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