Earlier I was just thinking about detecting double spends and I didn't think further about actually knowing how much has already been pledged.

It is possible to fulfill the assurance contract even if you don't know how much each input is worth but that's not a road I want to take: it involves bringing in all pledges together in one transaction, submitting it to a bitcoin node and if it somehow gets in a block then we know that we had enough pledges. But this has so many downsides that I won't try this.

Agree, this will be needed here.

I'll wait till this is implemented in bitcoinj, especially if the code's already written

There also needs to be a distinction to know if the assurance contract sends the bitcoins to an address owned by that wallet or not.

The way I imagined this is that people can create assurance contracts on a website for a certain amount of bitcoins to be sent to a certain bitcoin address that they choose. The server manages the collecting of pledges and creates the actual transaction when there are enough. At no point will it be able to spend any of the bitcoins, which I think is a big plus as if the server gets cracked into then no one loses any bitcoins.

Creating more than one transaction as part of a spend would also be nice too for when an user does not have the correct output values in order to pledge (for instance user has a 20 and 30 BTC transaction but wants to pledge 25 BTC)
But I won't worry about it for now as this is not really needed, just a nice bonus

Thanks, you're helpful as always Mike

This seemed to work, I never thought of adding the pledges to the wallet of the person making the assurance contract since they aren't actually valid transactions (input < output).

I haven't been able to work much on this: only a few hours during the weekends.

Bitcoinj seems to work perfectly for the client (with some changes) but I've been thinking about the server now: I don't think either bitcoinj or the satoshi client have an easy way to know if a certain transaction output is spent?

This is needed so that when there are enough pledges the final transaction can be made with only valid, not already spent, inputs and broadcasted to the bitcoin network.

The foundation site seems to be down now?

Tried locally and on downforeveryoneorjustme.com

This is a great news and I am happy that such a foundation exists with as purpose to help bitcoin grow.

From the letter page:


Those are great goals which I'm more than happy to help fund.

Out of curiosity, I wonder if Gavin's salary will be paid in bitcoins

And for the doomsayers: the foundation does not suddenly have control over all your bitcoins or bitcoin in general. Bitcoin is, and will stay, an open source project. Every single change is publicly viewable and a lot of people do look at them (I do every now and then). If something were to change bitcoin so that it is not bitcoin anymore, then a fork would be quickly created.

Besides, as time progresses, we will see more and more alternative clients too. So it will not simply be a matter of changing the main client, but also convincing the developers of every other client too.

I wish I won 4 BTC then.

The max bet is 10BTC though (for blackjack, I think it's the same for video poker), so if you do get a royal flush then you're looking at 8000BTC.

Thanks, it's appreciated

I didn't know about this BIP. I looked at it and at first glance it seems good: there is a transaction that needs to be signed. But I don't think it will work for this use case: every user wants to add transaction inputs to this, not just sign them. And they need to be signed using "anyonecanpay".


Thanks You convinced me to use the bitcoin p2p network itself. I do like the idea of an insurance contract being just a file you can download (which is also what Kjj suggested in his post). Your protobuffer example made this really clear how it can work. This makes the client/pledge application able to work more independently and not tied to one particular server.

I've played around a bit with bitcoinj earlier today (while also brushing up my Java knowledge, it's been a while). From a quick look at the source, it seems that creating the contract transaction would already be possible, but the signing of inputs using anyonecanpay isn't possible yet?

I wanted to bump this thread to thank Libertaad for his helpfulness for technical things outside of bitZino.

As a way to say thank you, I decided to "donate" my bitcoins to bitZino and found the following display glitch:

(I blackened out my total balance on there)

I don't want to start a language debate here as there are a lot of arguments made already both in favor and against Python. As an Ubuntu user though, a lot of applications I use are made in Python and they work just fine.
The biggest downside is probably portability of a GUI-framework: GTK is horrible in Windows and no idea if it even works on Mac OS X. Qt is probably a better option here, but I don't have any experience with this.
C++ would be the best option here, combined with Qt. But I'm only good with Python and .Net.

True. Ideally you would just have a website where people can send bitcoins to a certain bitcoin address to pledge how many bitcoins they want and it would not work any differently than sending bitcoins to a normal bitcoin address.
But I doubt something like that is possible.

I already noticed that Making this proof of concept was easy, but I've been thinking about how to progress and while there are different ways, they aren't as easy.

I was thinking about something similar, except without any blockchain at all on the client side. Since there needs to be a central server anyways to collect all signed inputs, that central server can keep track of the blockchain too.

I imagine something like that: a webserver like kickstarter where people can see all the projects they can pledge bitcoins to. If someone wishes to pledge to a project they can use a client application. This client application is very basic:
1) It creates a new bitcoin address and asks the user to send bitcoins to it.
2) It notifies the server about this address: when bitcoins are sent to it, the server will let the client know and the client will sign a pledge for the assurance contract and send it back to the server.
3) Whenever the server got enough pledges it'll broadcast the final transaction to the server
4) If there aren't enough pledges and the user wants their bitcoins back then the client can create a new bitcoin transaction and send it to the server who will broadcast it.

This is, I think, still safe since the private key to this new bitcoin address is kept in the client application and the server never gets access to it.

Using bitcoinj to directly connect to the bitcoin network would make some of those steps unnecessary, at the cost of the client having to handle the blockchain. I'm not really sure that extra cost is worth it, even if it goes a lot faster than a full node.

Also, with protocol buffers, you mean to use that for the communication between the client and the server, right? If so, why not just use a http server and json? I don't know much about protocol buffers except from looking at the examples.

Thanks for your thoughts

Hello everyone,

After seeing Mike Hearn's talk at the conference I wanted to play a bit with some of that stuff so I started working on an assurance contracts proof of concept.

Using bitcoin 0.7 and the raw transaction API I got this working on testnet-in-a-box. I haven't tried this on the main bitcoin network.

This is a small python script that does three things:

1) Creating a new assurance contract.

2) Adding pledges (this should be done by the various people wanting to pledge some bitcoins):

3) The person that made that contract needs to collect all inputs from everyone and put them in a single text file.
If there are enough pledges they can be combined and the final transaction sent to the bitcoin network.

This is still very much a proof of concept: command line application, having to share inputs, big strings that needs to be copied around, ... But it works

The code is on https://github.com/titeuf87/btcassurance
Parts of it are copied from bitcoin-python, pynode and pywallet.

I think the next thing for this is to divide it in a server/client model: a server that holds assurance contracts and a client that allows people to pledge bitcoins to one of those contract and send a signed input over.

Hello all,

I'm looking to purchase a gift card from amazon.fr for an amount of € 25.

I used to use spendbitcoins.com, but they stopped this

Any other similar service like this? Or anyone willing to purchase me one? If so, please let me know how many bitcoins you want. We can go through an escrow (not sure about what escrow services are there though) or if you look trustworthy then I can send the bitcoins first.

If you want to do this but can't read French I can show you how to do it, the site is very similar to the amazon.com one.

Thanks!

I haven't had the chance to play with real bitcoins yet, but I did with play money and I noticed a small bug: while the ball is spinning, it is possible to click on clear bets button. This increases your balance again, although once the ball is done spinning it gets corrected and you see the correct amount again.

Also I agree with Casascius's about the popup dialog: I think it would be better if it only shows when you click on an already placed bet. Although you already answered that point

For the rest, great job! I love the clean, minimalistic design of bitZino and the way roulette is implemented fits in nicely.

Fair enough! Thanks for the replies.

Great to hear the site's doing great! I've been having fun with those 0.25 BTC

I do have a small suggestion: could you add a way to see how much you've won/lost per game and total you've deposited and withdrawn? It was easy to add them up myself before when I only had a few deposits, but now it starts taking some work...

Aww ok, I hope you get it fixed soon

About Amazon: is it just the .com one that's suspended and the .fr one still works?

I guess I should have asked that before placing my order, heh.

Hi Jeremy,

Your site seems to be acting funny: I wanted to purchase something from Amazon. I wrote down my email, the country (France / EUR) and put in the required amount.

When clicking on submit I get pointed to a blank page and nothing seems to happen. I checked my e-mails too but didn't receive any either.

I was playing around on your site earlier, nicely done

One thing that was not obvious for me was how to withdraw: after I've won I wanted to stop playing and withdraw my bitcoins. I clicked on the withdraw link at the bottom of the page and there my bitcoins were shown under "Total balance" and "In-game balance", but not under "Available for withdrawal."

It took me a little bit to figure out I had to go back to the table and click there on leave.

Also, (just something small): if you're on the withdraw screen and click again on the link to withdraw at the bottom of the page, the "Back"- link just goes back to the withdraw screen. I would think that from the withdraw screen if you click on back you always go back to the table.

Oh...didn't think about checking the fees since the client suggested to add a fee to some and not to others. I thought the defaults were ok.

I changed the settings to always include a fee and now it works great!

Thanks And enjoy my bitcoins I'll end up losing on your site!

It seems to be better now, I had three bets reply right away.

But some bets just seems to get stuck.

Take the following for instance fb6553405beb57ba270df9814adcfc63b94e6a5be5546b2e519255b0ed557fc8
Look at both the bet tx and the payment tx: it took around 20 minutes.

Now I have another bet which satoshidice hasn't picked up yet: ff6a2dedc9fd31194806ba8aec7236d32cd4666a5b77fcdc7e01d38bb3cb3b72
That one shows up on blockchain.info, but not on the satoshidice website. on the home page when I look at processing status I see that that the last processing pass is from 22:52 with age 4 (that is the number of tx left to process?)

I hope you manage to resolve those problems too