Bitcoin Forum

I'm thinking of setting up an e-commerce store selling books for bitcoins, but waiting for the six confirmations to minimize my risk of a double spend attack.  Does anyone know of any charts out there that list average confirmation time for the six confirmations to occur?  My wish list for these charts: two charts, one that shows average amount of time to get six confirmations without any transaction fee, and another to show average amount of time with a transaction fee.

My concern is that I'm okay with waiting a day or two for the confirmations, but with typical e-commerce being instantaneous, customers would likely be frustrated and leave and I'd get no sales if this is common. 

Avg is one hour for 6 confirms.

You do know that to make a "fake" transaction go through even 1 confirmation requires the scammer to mine a block?

You have a good point.  That raises a larger question: what are best practices for website hosts who want to sell items for bitcoins?  If SoftballSuperstar is right about it only being about an hour, that's not a bad wait.  Which raises another question: if I were to go this route, ideally, I'd like to automate it so I'm not having to manually send emails after six confirmations happened.  Are there any tools / web services that will let you know when a transaction hits the six confirmation mark?

Yeah there are lots of tools and web services. You need to be more specific with your question. What programming language are you using to develop your site? What shopping cart script are you using?

There is a set of PHP libraries that do this:

http://bitfreak.info/?page=tools&t=bitsci

If you are using an ecommerce shopping cart script it might have a bitcoin plugin/extension/addon. For example for woocommerce:

http://wordpress.org/plugins/bitcoin-payments-for-woocommerce/

If you want to develop something from scratch you can use the blockchain.info api:

http://blockchain.info/api/blockchain_wallet_api
http://blockchain.info/api/json_rpc_api

(Yes there are two separate ones)

Or use the one built into bitcoind:

https://en.bitcoin.it/wiki/Original_Bitcoin_client/API_Calls_list

So lots and lots of options.

Thanks, this is really useful.  For my purposes, it looks like the Bitcoin SCI tool would be the best option.  The reason I'm not more specific is that I'm still in the initial planning stages - I haven't even built the website yet.  I'm planning on using Joomla as the CMS and I have a domain already bought, but other than that, I don't have any plans.  Joomla uses PHP, so it should go nicely with Bitcoin SCI.  I appreciate all the links, this is really helpful.

As far as the shopping cart itself, I'm thinking of using OpenCart, but I haven't decided yet.

For Joomla you should checkout this:

https://github.com/mikegogulski/bitcoin-virtuemart

That looks awesome.  The only feature that I wish they had is the ability to peg the price in bitcoins to USD.

I've looked into this a bit and the software that this plugin relies on is end of life. The plugin will have to be updated completely to support Joomla 2.5 and virtuemart 2. I am a web developer and I could do that and also add the USD based prices you want. Would you like to hire me to do that :)?

between 10-40 mins normally :)

Andy B

Abdussamad, I might take you up on that later on, but not now.  PM me your rates and email address and I'll get in touch with you later on if I decide I'd like that upgrade.

Also, I should add that if you're up for this at a later date, it would have to be less than $70 because there's a Joomla plugin that installs OpenCart for that much and there's already a free OpenCart bitcoin plugin out there.

$70 is too little for custom work like this. You should go with opencart. Good luck  :)

Yeah, I figured as much.  It doesn't seem worth the hassle when something equivalent already exists to me.  Thanks for your help, I appreciate it.

just did a transaction (6 confirmations were required), it took 40mins

You cannot define the exact time, or even average, as sometimes it is in a half hour, sometimes it takes even 2 hours.

There are two separate questions here:
1. Once mined, the average time for 6 confirmations is, by design, going to be around hour.  That is adjusted every, roughly, two weeks by the change in difficultly.  The variance is an issue here of course, but it should be within 1-2 hours to get that many confirmations.  Again, that is once mined.

2. The other question is what is the average time to get 6 confirmations including the time between when the transaction is submitted and when it is first mined.  That is dependent on a number of factors, including if a fee is paid, the priority of the transaction (which includes the size) etc.  This would be the average time of one hour, plus the time waiting for the transaction to be mined.  The statistics for how long it takes a transaction to be mined will vary as above.  [Edit: e.g.  this depends on the number of inputs, the number of bitcoins (e.g. if you are selling an antique book for 1000 Euro (4 BTC from one output), you will get a much faster confirmation than if it is 0.0004 BTC from 50 different outputs because of the priority. etc) ]


A few other notes:
a. if you are truly selling "books for bitcoins" (not ebooks or something electronic), you can afford to wait much longer since you will no doubt have many hours to confirm the transaction prior to shipping.  Even if you waited a day to ship, that wouldn't be an issue.  You can accept the order when submitted, and ship once the transaction confirms.

b. If you require payments to include appropriate fees, you will get a much faster confirmation.  And you can say something like "transactions that do not include fees do not ship until confirmed.  Transactions that include fees ship much faster."

Make sense?

6 confirmations in the long run would slightly take less than 1hour. However, bitpay does offer no confirmation transaction. It is still done on chain but if the transaction has been propagated well and the network has no competing transaction, it would be pretty safe to be secure against most doublespending attacks.

Even though guides and blockchain says average time is 30 minutes for 3 confirmations, I feel it is around 1.5-2 Hours for 6 confirmations, from what I have experienced.

It took me 1 hour and a half to transfer some coins to Kraken with 6 confirmations. The first 2 confirmations were really fast (about 5 minutes) and then it stuck at 5 confirmations for about 40-50 minutes. It was the first time i send money with 6 confirmations and i got really scared that something bad happened. Eventually i got the 6th confirmation and everything ended up allright.

i too have found that lately when i send coins it takes forever sometimes for the tx to confirm. i add the correct fees, it's just that the blocks can be 30 minutes or more between each other. maybe it's just bad luck, who knows.

The goal blocktime of bitcoin is 10 minutes.  For 6 blocks to be solved, it will take 60 minutes if the overall mining power is the same as when the last difficulty change happened.  Usually it has slightly increased, so it takes slightly less than one hour - by design.

Your total for 6 can be on the lucky side 30-40 mins, on the unlucky side up to 4 hours... but since your physically mailing a physical product, that shouldn't be a concern as don't put the book(s) in the post (or FedEx/UPS/DHL) etc until you sure the coins are in/valid.

I think 3 confirmations are more than enough unless the price of purchase is more than 500 BTC. And normally it takes up-to 40-60 minutes.

for small amounts 1 confirm is ok, for larger amounts 3 confirm. 6confirm would take around 1 - 1.4 hours