This patent is for executable QR codes, ie, actual byte-code instructions encoded in a QR code. This doesn't affect Bitcoin or anything else using QR codes for URIs or IDs or any other kind of non-executable data.

Aha! So I'm not just hallucinating the whole bitcoin URI support thing. Why doesn't it work the proper way, I wonder?

Huh. What happens if you drag-and-drop a bitcoin URI link onto the Bitcoin-Qt window?

What happens if you just run "bitcoin-qt bitcoin:somerandomaddress" from the command line (while Bitcoin-Qt is already running)?

Bitcoin-Qt does fully support bitcoin URIs, and has since version 0.6.0, it just doesn't doesn't automatically register itself as a URI handler. You can register it manually if you want, and even if you don't, you can still pass bitcoin URIs to it as a command-line argument or drag-and-drop bitcoin URI links onto the Bitcoin-Qt window.

What version of Bitcoin-Qt are you using?

Really? I guarantee that if you ask everyone you know if they've ever had some kind of serious problem with a bank or payment processor, you will hear some sad stories. If not, you obviously don't know very many people.

Not everybody has to store their bitcoins on their computer. Secure hardware wallets are under development to address precisely this concern. Or people can trust a third party service such as an e-wallet to handle their bitcoins, preferably with someone to sue if things go wrong.

Because I can, if the service is simply "I give you the money and you give me the goods". Many stores will actually offer a discount on big-ticket items if you pay in cash, simply because it avoids them having to pass the payment processing costs onto you, the consumer.

No, the point is that you don't have to trust anyone other than the person you're doing business with. You don't have to trust the bank not to freeze your account, you don't have to trust the payment processor not to reverse the transaction, you only have to trust that the person you're giving your money to will hold up their end of the bargain, exactly as if you had used cash. And really, isn't that the way it should be?

I've had my bank account frozen once (for completely arbitrary reasons), and let me tell you, it is not a fun situation to be in if you need a large amount of cash in a hurry.

This is completely false. Bitcoins are taxable, and while it may be easy to hide your bitcoins from the taxman, hiding the things you're spending them on is less easy. That's how tax evaders are usually caught: people spending lots of money that (according to their tax return) they don't have.

But would he want his money to be tracked if there is not an investigation? Many stores already do this every time you use a credit/debit card to try to build a profile on you that they can sell to advertisers and who knows who else. Some people don't like that.

I consider a 3% fee too much, especially if I can get the same or better service with a reduced fee, and I think most consumers would agree.

It's also useful for in-person transactions or transactions with trusted merchants where you know you're not getting scammed, and where paying an extra fee for the ability to reverse a transaction that you know you're never going to reverse is a waste of money.

When traditional banking "recovers" your stolen money, where do you think the money comes from? It isn't usually recovered from the thief, instead it comes from all those extra fees you pay, that you wouldn't be paying with Bitcoin.

There's nothing special about it: a coinbase transaction can have an arbitrary number of outputs, just like any other transaction, as long as the sum of all outputs is less than or equal to 50BTC + transaction fees. There is no requirement for the entire block reward to go to exactly one address.

However, the relationship between entropy and energy is one of the few things we do understand.

That's so cool! It'll be just like Star Trek! Except in Star Trek people had to say their passwords in a loud clear voice. Granted, the computers had voice recognition, but that didn't stop anyone with a tape recorder from taking over the ship. Okay, maybe it shouldn't be completely voice controlled...

Buy bitcoins, of course. As all time-travellers ought to know, it is impossible to alter history due to the Novikov self-consistency principle. Though that doesn't mean that killing Hitler is impossible, as long as you do it in a way that doesn't alter history:

With open Wi-Fi, anyone else using that connection can see everything that anyone else on that connection is sending and receiving. Regular HTTP traffic is unencrypted and is not safe to use on open Wi-Fi, but HTTPS is encrypted and secure. SMTP email is also unencrypted and unsafe, but ESMTP and POP3 have optional TLS/SSL encryption - make sure you enable it if you email provider supports it.

TOR traffic is encrypted, but is viewable by the exit node operator, so you shouldn't use TOR for unencrypted protocols such as HTTP and SMTP, regardless of your Wi-Fi security. TOR hidden services are fully secure.

Note that Bitcoin does not require encryption to be secure - everything transmitted is going to end up in the publicly viewable blockchain anyway, and is protected from tampering by hashing and digital signatures.

Also, when using secure Wi-Fi, check what type of security is being used: WEP can very easily be cracked with standard tools, and should not be relied upon for security. WPA/WPA2 is safe.

They seem to have a strange definition of "future". FPGAs have been the standard tool for large-scale brute-force cryptanalysis for ages.

I just compiled this on Linux, though I had to rename the time variable since it conflicts with std::time(). I'm not sure how you got away with that on Windows. Does the Visual C++ standard library really not have a time() function? Although, knowing Microsoft, that wouldn't actually surprise me. Also, I don't quite understand the "enthusiasm" thing. Is this just some random thing you threw in just to show your instructor that you know how to use a switch statement?

Anyway, to anyone else who wants to try it out, the code is clean safe, but I'd be wary of the included EXE file. I don't know whether it was compiled from this source or not and am too lazy to find out. Compile from source to be safe.

It's not a Windows executable, it's a Visual Studio solution file... and only the solution file, without the corresponding project file or even the source file(s). Algar, didn't it strike you as odd that your RAR file actually takes up less data than your post about it?

Lack of supply in a base currency isn't a problem, in fact, it is a requirement for currency to function. People will only accept something as payment if they want more of it than they currently have. Imagine if you will a planet made entirely of solid gold. On this hypothetical planet, everyone has as much gold as they could ever want and then some, so nobody would have any reason to accept it as payment. Trying to buy something on this planet with gold coins would be like trying to buy something on Earth with a handful of dirt. The excess supply of gold makes it worthless as a form of currency. Currency can only have value when it is scarce.

The purpose of the cloud supercomputing is not to regulate the money supply, it to secure the network. The money supply isn't actaully "regulated" at all, in the traditional sense of the word. There is simply a fixed money supply which is distributed according to a fixed schedule to the people who contribute their computing power to the network.

It is true that miners can arbitrarily decide which transactions get included in a block, but there are few things to keep in mind:
1) Miners cannot forge or alter transactions; a transaction must be included exactly as it is, or else not at all.
2) Transactions that do not make it into the next block are still "remembered" by the network, and may be included in a future block. If one miner refuses to process certain transactions, this merely results in the transaction being delayed until a block is found by another miner who does decide to include the transaction.
3) Miners collect transaction fees. It is always in a miner's "best interests" to include all fee-paying transactions no matter what, since including a transaction requires no more work than not including it.

The newest blocks are not automatically accepted. For a block to be accepted, it must meet the proof-of-work requirement and must not contain any invalid transactions. Additionally, if two conflicting blockchains are received, the one with which required the most work to produce is accepted, regardless of which one was received first.

Blocks are not fungible. Each is unique and impossible to forge. Any kind of "shared recognition" of blocks produced at the same time is impossible since the two blocks will contain different transactions (at the very least, the block reward will be paid to different addresses).

The reason Bitcoin requires a huge amount of processing power to create blocks is to force attackers to expend an equally huge amount of processing power to modify existing blocks, and since each block includes a hash of the previous block, it's impossible to modify a historical block without re-creating all the blocks that came after it, which requires even more processing power. If there was no processing power involved, what's stopping an attacker from just changing arbitrary blocks whenever he feels like it, eg, to facilitate a double-spend attack?

Transaction fees vary depending on several non-obvious and seemingly arbitrary factors. If you have recently received a large number of small payments (eg, from a faucet), these coins are considered "low priority" (to discourage people from spamming the network with such transactions) and spending them requires a higher fee than normal. Also, transactions requiring several "input" coins take up more data, again requiring a higher fee. It's semi-random which coins the client uses when making a transaction, so the fees will appear random as well, but there is a method to its madness.

The standard wallet encryption encrypts your private keys, and only your private keys. Your private keys are not necessary to tell how many bitcoins you have, since all transactions are public. There is no financial privacy (in the traditional sense of the term) when using Bitcoin. This is the price you have to pay for a zero-trust payment system. Since there is no bank or other trusted third party to verify transactions and account balances while keeping them secret, everyone needs to be able to see everyone else's transactions to prevent people from fraudulantly spending money they don't have. To protect your privacy, you need to ensure that your identity cannot be linked to your bitcoin addresses.

It is most unlikely that you will specifically be targetted by hackers if you have a considerable amount of bitcoins. You more likely to be targetted just for having Bitcoin installed at all, in order to get whatever little money you have. However, the chances of this happening are very low. In fact, I don't think anyone has ever had bitcoins stolen as a result of a keylogger being used to get the passphrase to a stolen wallet.dat file using the standard wallet encryption (though it's not impossible, and additional encryption is useless againsts a keylogger).

A good idea, just remember that encrypting your wallet isn't the whole story if you're worried about your privacy rather than just having your money stolen.

Correct. However, the OP's question indicates that he is concerned about keeping has balance secret, which is something that encryption won't help with if his identity can be linked to his addresses some way other than his wallet file.

Note that Bitcoin addresses and transactions are inherently public, and the only thing that's private (and the only thing which needs protecting with encryption) are the private keys used to sign transactions. Anyone who knows your addresses can see how many bitcoins you have, where they came from, and where they're going. Privacy is only achieved by the difficulty of associating Bitcoin addresses with real-life identities. You can encrypt your entire wallet using Truecrypt or EncFS if you really want to, but be aware that this might not provide as much protection as you think.