fee for short transaction #1491

Hi!

I set up bitcoin for the first time. Someone gave me 0.01 btc. As a test I wanted to send 1 ubtc. The client said:

"This transaction is over the size limit. You can still send it for a fee of 0.0005, which goes to the nodes that process your transaction and helps to support the network. Do you want to pay the fee?"

The example transaction in https://en.bitcoin.it/wiki/Transactions has 378 bytes. I don't believe my transaction was over 10.000 bytes. Rather I believe, the fee was enforced because the output was smaller than 0.01 btc.

Please write the correct reason for the fee when asking for the fee.

If the message was made less specific— and thus less misleading— would that mostly address your concern?

E.g. "This transaction is too small or difficulty to process for it to be distinguished from an attack on Bitcoin. You can still send it for a fee of 0.0005, which goes to the nodes that process your transaction and helps to support the network. Do you want to pay the fee?"

On 06/20/2012 08:50 PM, Gregory Maxwell wrote:

If the message was made less specific— and thus less misleading— would that mostly address your concern?

I'd prefer to have a specific message for each situation, so the user knows what's causing the fee and can act accordingly.

If this is difficult, then stating all the possible reasons is ok.

E.g. "This transaction is too small or difficulty to process for it to be distinguished from an attack on Bitcoin. You can still send it for a fee of 0.0005, which goes to the nodes that process your transaction and helps to support the network. Do you want to pay the fee?"

Explaining that very small transactions might be used in an attack and a fee solves this problem is excellent. Your first sentence appears a little weird, though (apart from the typo s/difficulty/difficult). How about: "To avoid attacks on Bitcoin a minimum fee of 0.0005 is required for transactions under 0.01. Do you want to pay the fee?"

If the reason is a large size, then printing the size might help to decide if it's worth trying to make the transaction size smaller.

Bernhard

Encrypt emails. My GPG key is on public key servers.

The 'size' in question is the data size, not the transaction value— and their relationship is chaotic if not outright byzantine. :)

The reason I asked about the vague message is that it's actually quite hard to give the "real" reason in some cases. E.g. say you have a 100 BTC input unconfirmed (so it won't use it), and 100 btc in 1e-8 dust inputs. You go to do a 10 btc transactions and the selection will ignore the 100 BTC unconfirmed input, then build a TXN which is too big to be permitted out of dust inputs. .. then come back and tell you that your transaction data was too big when the "real" issue was that the 100btc input wasn't confirmed yet. There are a dozen variations of this.

Another similar case is, consider that you have two possible transactions: one has 2 BTC in change, but will require a 0.0005 fee (because of its low priority or data size)... Another would have 0.000001 BTC in change but require no fee except the change output of less than 0.01 means a fee of 0.0005 would be required— so instead the system proposes you give up the 0.000001 change as fee thus avoid hitting the 0.01 rule. If it says "a minimum fee of 0.0005 is required for transactions under 0.01" you'll be thinking "what the heck, my output was >0.01, and that fee is much less than 0.0005!"

So I think that we probably can't give specific understandable messages for all cases. We can probably give better messages for some, but we will need good generic text too. So any suggestions on comprehensible generic text would be helpful. Crafting this kind of text is hard.

That message doesn't exist anymore with the new confirmation dialog. Now it simply states the fee that is needed. It does not try to explain why, as that is a lost cause here.

With coin control you can manually (un)select inputs and get some insight into the transaction (byte) size and when a fee is needed or not.