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1041  Bitcoin / Development & Technical Discussion / Re: QR Code Best Practice on: April 20, 2013, 03:49:40 AM
Which makes most sense in case anyone knows?

 - http://en.bitcoin.it/wiki/BIP_0021#Examples
1042  Economy / Economics / Re: Buying big amount of BTCs- possible? on: April 20, 2013, 03:42:54 AM
I just wanted to know e.g what happens if I wanna buy like 100, 1000 or even 10 000. Just bitcoin market theory,

When you are trading on a market exchange like Mt. Gox, settlement occurs immediately.  In other words, every bitcoin that you buy is transferred to your exchange account immediately.   There is no delay on settlement, there is no cancellation, etc.   The bitcoins are credited and sitting in your account balance.

Now when you withdraw those, you are simply making a request to the exchange.  Your exchange account is a hosted (shared) E-Wallet account.  This means that you don't control the wallet.  The E-Wallet provider controls the wallet.    So the bitcoins you requested to be withdrawn are sent when the exchange/E-Wallet provider processes your withdrawal request.  That normally is relatively instant (e.g., in under a minute or a few minutes).   Because of security precautions, they may occasionally run out of coins in their hot wallet and may need to retrieve more funds from cold storage.   Think of this as withdrawing cash from a bank teller.  Smaller withdrawals can be handled normally, but sometimes large withdrawals require a delay as the funds need to be moved from more secure storage.    That can be a delay up to several hours or a little longer, depending on how the exchange/E-Wallet provider manages their cold wallet.

As far as your local wallet, (e.g., running Bitcoin-Qt/bitcoind), there is no limit as to how much it can hold.  

The exchanges all have daily withdrawal limits due to AML restrictions, so if you were to buy 10k BTC, that entire amount couldn't be withdrawn all at once.  At Mt. Gox, for instance, the limit for verified accounts is 1,000 BTC withdrawn per day.     A higher limit is available with an even higher level of AML verificatoin called "trusted" status:
 - https://support.mtgox.com/entries/20919111-AML-Account-Statuses

If your question has to do with what impact on the market do purchases of these size cause?  It depends on the exchange.   At Mt. Gox even you would probably want to stagger a 10K buy, or not, depending on market conditions and your preference as to how soon to complete the purchase.   Clark Moody site has a calculator to show "slippage", so you know how much it costs for a larger purchase.
 - http://bitcoin.clarkmoody.com  <-- Click "show calculators" and then enter the dollar amount you are looking to spend.
1043  Bitcoin / Bitcoin Discussion / Re: Jerusalem Post: Bitcoin is for terrorism on: April 20, 2013, 03:27:36 AM

LIGNET just did the same thing:

Bitcoin Virtual Money Opens Door for Terror Finance
 - http://tinyurl.com/d2urh4z
1044  Economy / Currency exchange / Re: Walmart Giftcards on: April 20, 2013, 03:14:17 AM
I'm looking to buy around $800+.

Are you in the U.S.?  If so, you can convert your bitcoins to Dwolla (e.g., Camp BX, Mt. Gox, FastCash4Bitcoins.com, #bitcoin-otc marketplace, etc.) and then use those funds at Lyoness to buy gift cards at 1:1 (i.e., an $800 Dwolla transfer gets you $800 of Walmart gift cards).

Purchase Gift Cards for Merchants in USA
 - http://bitcointalk.org/index.php?topic=156968.0
1045  Bitcoin / Development & Technical Discussion / Re: Solving the fast payments problem on: April 20, 2013, 12:49:21 AM
*) Naive implementation could open a potential denial of service, a rogue node sending over and over double spends of the same transaction. So you need to forward just one 2nd spend, not any of the following. The merchant needs to know that a double spend is in progress, not it's details, so races among 2nd, 3rd... spends are irrelevant. If any of the racing doublespends arrive at him, he fails the sale and holds the merchandise.0

Your node's memory pool has a transaction with inputs A and B.  Then received is another transaction with inputs A and C.  
So your node prefixes this second transaction with the first and relays this pair.

Then to another node the attacker has the transaction with inputs A and D.  
Your node will not relay that but other nodes that haven't learned of the transaction with A and C will.

At the same time the attacker relays a transaction with just an input D.

Your node learns about the transaction with D and relays it.

So, some nodes then have the transactions [A+B], [A+C], and [D]  but will never know about [A+D].    If a merchant relies on this node and accepts [D], that merchant loses if [A-D] gets included in a block.

So this doesn't really eliminate the risk, it just makes the attack a little more complex.  
1046  Economy / Service Discussion / Re: Coinbase business model on: April 19, 2013, 10:04:56 PM
The exchange cannot be manipulated by false orders.

I'm not sure I entirely follow.   There are people who have discussed emptying their bank account so as to cause the Coinbase ACH to get a return code for NSF, after buying at a higher level and then later seeing the BTC/USD exchange rate at a fraction of that level. 

That essentially is a fake order, and Coinbase then is left holding the bag on the expensive bitcoins the buyer bailed on.  Additionally, Coinbase incurs a fee I believe for that NSF.

So they definitely take a risk with their current model. 
1047  Bitcoin / Bitcoin Discussion / Re: Is Bitcoin Safe For Business? on: April 19, 2013, 10:16:29 AM

That discussion is incomplete without double spending attacks, especially if payment is recognized on 0/unconfirmed.
1048  Economy / Service Discussion / Re: I thought my wiki account was grandfathered regarding the anti-spam measures... on: April 19, 2013, 01:39:16 AM
My account at https://en.bitcoin.it/wiki/ was created long before the paid anti-spam system was put in place, i could swear old accounts like mine that were in good standing had been grandfathered, but it seems it isn't...am i remembering things wrong or was there a decision to ungrandfather old accounts?

There's no grandfathering that I know of.

The payment for anti-spam protection by BitcoinPayment is 0.01 BTC, an amount now worth over a $1 which is higher than necessary to simply prevent wikispam.   
1049  Economy / Service Discussion / Re: MtGox - AUD -> USD? on: April 19, 2013, 12:38:04 AM
Obviously you cop a 0.6% fee each way in doing so.

In addition to the spread on each.  Though sometimes you can actually make a profit converting your AUD balance to USD ... just depends on what the order book looks like.
1050  Bitcoin / Technical Support / Re: Getting my head round it. on: April 19, 2013, 12:21:27 AM
Isn't that scary for people with huge amounts of coins.

Isn't what scary?  [Edit: Oh, ... your concern is over the address collision risk.  See below:]



 - http://i.imgur.com/fYFBsqp.jpg
1051  Economy / Service Discussion / Re: MT Gox AML No Response on: April 19, 2013, 12:06:39 AM
Can't help you with the AML questions, however:

Also is there an alternative to MT Gox to safely sell bitcoins and get the cash into fiat?

The factors that matter for any cash-out decision are:

 - Where are you located (country)?
 - How much are you looking to trade?
 - What type of cash are you looking to receive?
 - How soon do you need access to the proceeds?
 - Is privacy important?

A fairly comprehensive list of cash-out options is:

 - http://en.bitcoin.it/wiki/Selling_bitcoins
1052  Economy / Speculation / Re: The Weekend Dip Myth on: April 18, 2013, 11:00:40 PM
friday rally, then a weekend dip! get em while they're cheap.

Bah.  I think this myth is BUSTED.  It used to work.  There still might be conditions where it works.   It is not working now.

Buying back at over a 10% higher price sucks!
1053  Alternate cryptocurrencies / Altcoin Discussion / Re: A hard forked branch to accommodate bitcoin’s growth on: April 18, 2013, 10:05:13 PM
If coins are sent to an address in the new chain, they will remain in that chain.

Ha, nice try.   Delusional, but nice try.

The address is valid in both sides of the fork.  So let's say that somehow you trick me into spending my bitcoins that I received prior to the fork and pay using them to an address in your inflatacoin fork.  But then you can then use that exact same address on the Bitcoin blockchain side as well, broadcast my transaction there and receive the full value of the transaction there as well.

Participating on your side would be seen as the way to watch your bitcoins disappear.

Because there is no way to ensure that all transactions from the Bitcoin blockchain get into your inflatacoin fork, then the only time your chain becomes interesting to me is after my transaction confirms on the Bitcoin blockchain but where I've composed and sent a double spend of the UTXO used to your side of the fork, and then pay you with those funds which are now worthless on the Bitcoin blockchain.  That's a win / win for me!
1054  Bitcoin / Press / Re: 2013-04-18 FoxBusiness - Bitcoin Buzz Draws Western Union, MoneyGram on: April 18, 2013, 09:54:31 PM
Quote
Remittances go to pay for housing and for food and for maintaining your family," he said. "If you're sending to a rural part of Mexico, my guess is that the merchant is not going to be accepting bitcoins. They want pesos."
- Read more: http://www.foxbusiness.com/news/2013/04/18/bitcoin-buzz-draws-western-union-moneygram/#ixzz2QqtZN0Rb

Yup.  But instead of having to go down to the Western Union agent location to pick some pesos up, you send a text to your friend's sister who buys bitcoins and pays pesos in exchange.   That person makes a little from each transaction.  Western Union gets about $8 + a vig on the exchange rate, so for a remittance transfer valued  at $100 the remittance recipient might get just $88.      With the person providing independently money exchange, that same transaction might deliver $94 worth and the person providing the exchange makes at least $5.  Sure that's not a lot of money but six of those a day and that person would be making more with this side job than from other employment options.

1055  Bitcoin / Technical Support / Re: Getting my head round it. on: April 18, 2013, 08:47:51 PM
I had 5000 coins, I put them into a cold wallet. If some how the cold wallet's address was the same as a wallet already online on someone's PC if they decide to make that wallet come online would all the coins on the cold wallet get transferred to the online wallet.

The way it works is confusing because the plumbing underneath is actually different from how it is presented.

Coins don't actually get held in a wallet.   The blockchain is a transaction ledger, and every full node with a blockchain has a copy of it.  The only thing in the wallet on your client essentially is the private keys that allow you to spend the funds for certain addresses.

Because people are familiar with the term wallet, since there is one in most back pockets and purses, that's what the clients try to emulate.   So the Bitcoin clients use the same concept of receiving and sending money as you have with a physical wallet for cash, but that's simply not what happens.

When you send a payment, you are simply broadcasting your permission for value to be transferred from previously received transactions to new bitcoin addresses.

When you receive a payment, that is simply the client showing a filtered view of the blockchain ledger for a specific address.


So yes, if someone has a private key from a cold wallet and that key is already elsewhere in an online wallet, either of those has the ability to spend the funds.  The network only cares which one spends them first.   The second attempt will be rejected as the funds have already been spent.
1056  Bitcoin / Bitcoin Discussion / Re: DDOS Payback on: April 18, 2013, 08:30:44 PM
Is this a real attack or just exponential traffic growth?

Related:


 - http://news.netcraft.com/archives/2013/04/11/mt-gox-victim-of-own-success-as-bitcoins-fall-in-value.html
1057  Bitcoin / Development & Technical Discussion / Re: Forked block chain on: April 18, 2013, 08:04:09 PM
Your fork will have coins pre-distributed so you don't have the problems with early adaptors.

You might be overlooking the obvious. 

The spend transactions from the "pre-distributed"  coins would be valid on both sides of the fork.  Thus if bitcoin is trading at $90, let's say, and you are asking me to pay 10,000 ?TC for a pizza then I'm certainly not going to be using my pre-distributed coins and instead would only be using ones whose coinbase occurred post-fork.

And even putting that aside, you've got a fork that is extremely vulnerable to 51% attack.
1058  Economy / Service Discussion / Re: Blockchain.info is offline, what's wrong? on: April 18, 2013, 07:38:46 PM
Quote
Everything should be back online now. Again apologies for the downtime.
- https://twitter.com/blockchain/status/324963187957063681
1059  Bitcoin / Bitcoin Discussion / Re: Bitcoin circle image on: April 18, 2013, 10:47:30 AM
What do you think? Does it look too much like a cult because of the darker background?

Heh, the first thing I thought of:



The Carousel scene from Logan's Run (1976).  Renew!
1060  Economy / Trading Discussion / Re: What do you want from a better crypto exchange? on: April 18, 2013, 09:04:15 AM
  • Supports multiple cryptocurrencies (our initial goal is BTC/LTC/NMC/TRC)

You'll want to make sure you understand the risk of 51% with proof-of-work based currencies like Bitcoin and Litecoin.  The confirmation threshold for a merchant selling server hosting is one thing, the threshold for withdrawing bitcoins paid for using litecoins might be another.

I personally will not leave bitcoins with an exchange that has exposure to a Litecoin 51% attack.    I do not know if the exchanges that do trading between bitcoin and alts are taking additional precautions but an exchange wanting to grow market share (and revenue from fees) is more inclined to throw caution to the wind since it is primarily the customer's funds at risk to a 51% attack.   Preventative measures could be taken such as imposing a minimum delay before bitcoins purchased with Litecoin can be withdrawn, or daily limits such that if there is a Litecoin 51% attack, any losses are born from the exchange's reserves.
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