Bitcoin Forum

Hi,
I earlier brought 0.036 BTC from Coinbase, i have never had an issue with them before and the transaction is nearly always confirmed within 10 mins.

I sent 0.012 BTC to each of my Bitcoin addresses, this was 5 hours ago and the transaction is unconfirmed on all 3 addresses, I did pay the 0.0001 BTC charge.

Here are the 3 addresses i sent BTC too:

1N3M6kHTGdidAuFU8nWAqyqc6dnNUzcgW8
1HvubuW1TFjbkkVAcUNSJhSSKVKMbBcLWM
19EDDsRcopDPRp49g6VNHzMFqW8mUqN4Lv

This is the 4th time in just a couple of weeks, however the first with coinbase. I sent 0.1 BTC to a friend and the transaction never confirmed even though i paid 0.001 BTC charges, (10 X More then recommended ) the transaction eventually god reversed. This did not really give a good impression to my friend who i was introducing Bitcoin too.

Please can you let me know whats happening here, I'm starting to feel bitcoin is unreliable and slow.

Best Regards

There is a DOS attack against the blockchain going on right now.  It is causing transactions to take longer than usual to confirm.

In order to pull of the attack the attacker has to pay a higher than average transaction fee.  They will eventually run out of money and the attack will stop, but in the meantime you can send your transactions with higher fees to make sure that your transactions get confirmed instead of the attackers (which will force the attacker to spend through their bitcoins even faster to maintain the attack).

This is very interesting... so is this the issue for every transaction at the moment paying 0.0001 ?

Likely so. Like dannyhamilton said, there is a limit of sigops a block can have, if it's more than 20000, nodes will reject it as invalid. The attackers flood the mempool with higher fee, higher sigops transaction. Pools prioritize transactions based on the fees/kb. To pull this attack, the transaction fee must be higher than the average fee. The higher fee paid, the higher priority they have. This attack won't be successful if miners do not prioritize TXes with high sigOPS and fee or miners specifically prioritize some transactions.

Since your using coinbase to process your transactions you don't have the private keys to the sending address.

Your only option is to contact coinbase support and ask them to reverse the unconfirmed transaction and resend it with a higher fee than the attacker.

All transactions to those 3 addresses are confirmed.  I don't see any unconfirmed transactions in my mempool right now.

Sometimes the network is crowd and you need to pay higher than recommended fees to get the transactions confirmed otherwise it will take long time! You could check here cointape.com to calculate the fees.

The network was not congested at all when this happened. The advantage of this attack is that little fee is required to disrupt the networks since the size isn't big. The blocks at that time weren't filled up at all in terms of size but were filled up with the number of sigops. Eg. This transaction https://blockchain.info/tx/9e451c7d53ca42a15b4e55ca67e7defc4d941959255ca6b960f010e623949b51. It doesn't require a high cost if network isn't paying high fees.

As long as the Network is under attack.. just pay slightly higher fees or wait a bit longer.
Nothing to worry about.

great to see they finally got through.  very interesting info on dos attack on network must look into this more..... ;)

There is not much to look into the best thing you can do to prevent unconfirmed transactions is to pay a network fee slightly higher than the attacker.