[RFC] coins blocked by unconfirmed input - potential DoS

[zefir]

Dear Bitcoiners,

I ran into a stupid situation that prevented me to spend the coins from an address, since one input failed to get confirmed.

First I might need to say sorry if I missed to RTFM or it is a known fact. Otherwise this might turn out to be a reliable way to lock funds in an address and render them unspendable for some time.

This is how I ran into it: I am buying Avalon ASIC chips in 10k batches and distribute them to DIY folks in smaller volumes to support the de-centralization of ASIC mining. I use the blockchain for accounting, i.e. there is one common address (162HWpt9njiDsk5nwGixw7fDPuNy55Kh9X) all buyers send coins to and approve their order by signing with their sending address. As soon as the final balance in that address reached a threshold, I ordered the next batch and paid with the collected coins.

I process payments with piuk's MyWallet and everything went fine for several chip orders, but failed badly with my last payment. After sending all remaining coins (500+ BTC) for a partial payment from that address, several hours later I noticed it was still not confirmed. Investigated and found that one single input (out of 100+) was pending unconfirmed, holding the transaction in limbo. 24h later my payment transaction was canceled, but since I still see the problematic input pending unconfirmed, I am not able to sweep this address.

As the inputs to be used for an output are not selectable (at least in MyWallet), isn't this an easy and reliable scheme to prevent addresses from being swept: just send a small amount with no tx fees and get it stalled for 24h?


Any advice how to prevent this (other than waiting inputs to confirm)?


Thanks

[coastermonger]

Wow, really? That little bit caused the whole thing to get stalled up?  

I'm tempted to say the answer to your question might be "maybe" but what happens if you try to send out a smaller amount?

If indeed that prevents the address from being swept, it would be interesting that all I need to do is pay 1 unverified satoshi each day and my account is locked down

[zefir]

Wow, really? That little bit caused the whole thing to get stalled up?  

I'm tempted to say the answer to your question might be "maybe" but what happens if you try to send out a smaller amount?

If indeed that prevents the address from being swept, it would be interesting that all I need to do is pay 1 unverified satoshi each day and my account is locked down

Did that today, i.e. send the coins again, but reduced the amount by the still unconfirmed input. That worked, i.e. transaction got confirmed within minutes. Obviously the problematic input is left out for the transaction.

Problem is therefore limited to situations when you spent all coins (which sadly will mostly be the case in group buy type of fund collections).