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sirius
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March 02, 2010, 06:25:14 AM
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You're welcome to check out and comment on the exchange service I'm building at www.bitcoinexchange.com (auth: bitcoin/bit). You can test making an order, but it won't be completed and everything might not work yet.

I'm thinking about how I should solve a problem with the trade model I initially chose. That is, bitcoins or euros are reserved to the customer when he makes an order, without a guarantee that he'll really pay for it. That makes the service vulnerable to be DoS'd by some jackass who makes a buy order for all my bitcoins/euros and never pays. It also wrongly changes my pricing that automatically reacts to the amount of available bitcoins/euros I have. I have two solutions for this:

1) Keep the current model, but require more personal identification from the customer (i.e. make buying more difficult), so he's less likely to just be fooling around. Require registration and e-mail confirmation. Set an expiry time and a maximum amount for transactions. The expiry time doesn't help very much in the case of payment by bank transfer, because it must be at least a few days instead of 15 minutes or so.

2) Change to a stock-buying-like solution, where the customer can choose to get his coins immediately at the spot price when his payment is received, or he can set a maximum/minimum coin price at which he is willing to buy or sell. This removes the problem with reservation of coins, but is a bit more difficult for the customer. Some expiry time is also needed for paid minimum/maximum price orders that are not completed because the desired price is not reached in time. After the expiry time the order should be completed at the spot price or alternatively the payment should be returned (this causes some extra hassle).

So, which option do you think sucks less? Any other solutions?

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NewLibertyStandard
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March 02, 2010, 07:50:14 AM
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Your pricing calculation should only take into account your available balances after the transactions have been finalized.

I think the second option is better, but if you use the first option, you have to make it clear whether they're getting the rate when the order is placed or when the funds are received. And if it's at the rate when the funds are received, I'd recommend you emphasize that the amount is an estimation until the transaction is complete and also reserve additional funds to take into account the currency's exchange rate changing.

Another service which I think would be useful which might be what the other person who is creating a market has in mind, is to let users buy and sell from each other, with the site administrator working as a trusted broker. Sure, people can buy and sell directly from each other, but they may trust an established service more than a stranger. After two strangers agree on a price, they send funds to the broker who waits to receive funds from both users before completing the transaction. This would help people getting scammed by people taking advantage of the non-refundable attribute of bitcoins.

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sirius
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March 02, 2010, 08:25:17 AM
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Your pricing calculation should only take into account your available balances after the transactions have been finalized.

With the current model I need to take received orders into account when calculating the price, because otherwise the customer would have an incentive to make ten orders of 1,000 btc instead of one order of 10,000btc. For example, with my pricing 1,000 btc might cost 1€ but 10,000 btc would cost 11€ which is more than 10 * 1€.

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I think the second option is better, but if you use the first option, you have to make it clear whether they're getting the rate when the order is placed or when the funds are received. And if it's at the rate when the funds are received, I'd recommend you emphasize that the amount is an estimation until the transaction is complete and also reserve additional funds to take into account the currency's exchange rate changing.

That would be like the second option but without the choice to set a min/max price. It's true that I need to emphasize that only the current spot price is shown.

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March 02, 2010, 08:42:16 AM
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With the current model I need to take received orders into account when calculating the price, because otherwise the customer would have an incentive to make ten orders of 1,000 btc instead of one order of 10,000btc. For example, with my pricing 1,000 btc might cost 1€ but 10,000 btc would cost 11€ which is more than 10 * 1€.
That would be great to adjust the rate on a curve like that. Tonight I thought of a way for my available balances to affect my exchange rate average over time, but my calculation would only be based on my end of day balances. But I'm probably not going to implement my idea any time soon.

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March 05, 2010, 03:05:50 AM
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I decided to take the second option, I'll be working on it.

The 64bit version memory leak is fixed now, so you can notice the successful Bitcoin integration on the statistics page. Cool

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sirius
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March 16, 2010, 05:20:09 AM
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Lately I've had a lot of other things I need to work on, so it's been a delay with this project. I hope to get this done soon anyway.

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sirius
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May 23, 2010, 04:06:04 PM
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Welcome to buy, sell and give feedback at www.bitcoinexchange.com, it's now open for the public Smiley

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May 23, 2010, 09:03:31 PM
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are the different exchange rates for EUR-->BTC and BTC-->EUR correct ?
shouldn't they be the same ?

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sirius
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May 23, 2010, 09:53:07 PM
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are the different exchange rates for EUR-->BTC and BTC-->EUR correct ?
shouldn't they be the same ?

Yes, they're different. That's because of how the pricing adjusts to supply and demand. See the about-page for more details.

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May 24, 2010, 12:26:17 AM
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So the bank wire thing, I need an account in europe for that to be free?  It seems like I would need to exchange a ton of bitcoins to make the 30 euro fee worth it.

Is there some way I can establish an account online for that?

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sirius
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May 24, 2010, 05:21:29 AM
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So the bank wire thing, I need an account in europe for that to be free?  It seems like I would need to exchange a ton of bitcoins to make the 30 euro fee worth it.

Is there some way I can establish an account online for that?

Yeah, bank transfer is not very useful for customers outside Europe. I don't think they'll let you open a bank account online, the bank legislation is rather strict about customer identification.

I've been considering something like Pecunix or c-gold for foreign customers, but their exchange commissions are typically around 5% for buying and selling, and they add a difficult extra step to trading.

It's unfortunate that low-cost international payment methods are so scarce, but at least I'm backing up BTC so that people in Europe can trade with me, and then trade with people in the US via PayPal, hawala or whatever. Maybe I could do some trading at bitcoinmarket.com myself too.

Now that we have multiple exchange services, we'll only need Bitcoin 0.3 with the daemon and it's a good time to start advertising BTC to online service providers Smiley

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May 24, 2010, 01:29:48 PM
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I'd be more than happy to sell you Pecunix for bitcoins at competitive rates. I don't have any Pecunix available at the moment, but if you check back once a day, it won't be long until I have some more available.

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