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For most purposes, the risk of a double spend is negligible, and it's perfectly safe to accept an unconfirmed transaction. However, there are still those purpo

For most purposes, the risk of a double spend is negligible, and it's perfectly safe to accept an unconfirmed transaction. However, there are still those purposes for which that's not a good idea...

rebelidealist 13y ago
How would it be negligible? Seem like it can easily be done.
- nknighthb 13y ago
  It's pretty easy to steal and use a credit card, doesn't mean a lot of customers do it. For low-value transactions, it's not worth spending much time on. You save that for low-volume high-value transactions.
SwellJoe 13y ago
With no confirmations a double spend is easy (would require a custom Bitcoin client designed for the purpose). Is it likely? No. So, if I ran a coffee shop, I'd hand over the goods without confirmation. If I were selling a house or a car, I'd wait for a whole lot of confirmations. Digital goods probably don't need to wait, either, particularly for returning customers. So, yeah, I agree...I just want to be clear about why the risk is low: Because most people aren't going to cheat you out of a cup of coffee.
natrius 13y ago
To elaborate, a merchant can easily monitor (or pay someone to monitor) transactions being sent to miners in real time. The probability of a successful double spend decreases drastically as the time since the first spend increases. If someone hasn't tried to double spend in ten seconds or so, they'll likely fail if they try.
- lappa 13y ago
  This is simply false. Many mining pools allow you to push to transaction to them. If your first spend has a 0.0001btc fee and the second has a 0.001btc fee, they will choose the 0.0099btc fee. You cannot monitor transactions being sent to miners if they aren't propagated through the normal bitcoin network. Along with that, there have been cases where mining pools have doublespent unconfirmed transactions and stolen lots of bitcoins. GHash stole 3000btc from betcoin https://bitcointalk.org/index.php?topic=327767.0 https://bitcointalk.org/index.php?topic=327767.0
JohnTHaller 13y ago
For in-person, retail purchases, double spend is a big issue since waiting around for 10-20 minutes while the transaction is confirmed is unworkable.
- Smegger 13y ago
  A karmic based waiting period my be needed then; It could be based on age of address, transactions successful, repeat business with your address, amount of bitcoins spent per purchase, etc. With a higher score you could waive the waiting period for conformations or use less confirmations based on whatever algorithm you have. If some one is going to try cheating they probably won't be doing with and address they conduct regular business with.
- ksrm 13y ago
  Smegger, you are hellbanned.

For most purposes, the risk of a double spend is negligible, and it's perfectly safe to accept an unconfirmed transaction. However, there are still those purposes for which that's not a good idea...

rebelidealist 13y ago

How would it be negligible? Seem like it can easily be done.

nknighthb 13y ago
It's pretty easy to steal and use a credit card, doesn't mean a lot of customers do it. For low-value transactions, it's not worth spending much time on. You save that for low-volume high-value transactions.

SwellJoe 13y ago

With no confirmations a double spend is easy (would require a custom Bitcoin client designed for the purpose). Is it likely? No. So, if I ran a coffee shop, I'd hand over the goods without confirmation. If I were selling a house or a car, I'd wait for a whole lot of confirmations. Digital goods probably don't need to wait, either, particularly for returning customers. So, yeah, I agree...I just want to be clear about why the risk is low: Because most people aren't going to cheat you out of a cup of coffee.

natrius 13y ago

To elaborate, a merchant can easily monitor (or pay someone to monitor) transactions being sent to miners in real time. The probability of a successful double spend decreases drastically as the time since the first spend increases. If someone hasn't tried to double spend in ten seconds or so, they'll likely fail if they try.

lappa 13y ago
This is simply false. Many mining pools allow you to push to transaction to them. If your first spend has a 0.0001btc fee and the second has a 0.001btc fee, they will choose the 0.0099btc fee. You cannot monitor transactions being sent to miners if they aren't propagated through the normal bitcoin network. Along with that, there have been cases where mining pools have doublespent unconfirmed transactions and stolen lots of bitcoins. GHash stole 3000btc from betcoin https://bitcointalk.org/index.php?topic=327767.0 https://bitcointalk.org/index.php?topic=327767.0

JohnTHaller 13y ago

For in-person, retail purchases, double spend is a big issue since waiting around for 10-20 minutes while the transaction is confirmed is unworkable.

Smegger 13y ago
A karmic based waiting period my be needed then; It could be based on age of address, transactions successful, repeat business with your address, amount of bitcoins spent per purchase, etc. With a higher score you could waive the waiting period for conformations or use less confirmations based on whatever algorithm you have. If some one is going to try cheating they probably won't be doing with and address they conduct regular business with.
ksrm 13y ago
Smegger, you are hellbanned.