No preimage attack against SHA-2 is possible. 

Saying "it's already difficulty enough" is like saying it is already difficulty to walk through a wall due to quantum tunneling but just to be safe we should double up all walls in case someone gets "lucky".

Are you from 5 to 7 years in the future or are these GPU from imaginary land?

Top of the line GPUs are 28nm today.

I can use 2 more beta testers to purchase Bitcoins with cash at your local convenience store.
https://bitcointalk.org/index.php?topic=349418.0

It can be done.  It would be a rather extensive change so it isn't trivial.  It is highly likely that it will not be needed at least not in a lifetime.

There is ~$5T of currency in the world (M0 money supply).  If Bitcoin money supply was valued at $5T that would make 1 satoshi worth 0.2 US cents.  Even 25x that would put a satoshi at $0.05 ea and many countries have already removed their smallest currency unit from circulation. 

Global GDP is much slower more like ~1.8% annually.  If Bitcoin replaced all other forms of currency and was used universally everywhere the purchasing power would only rise by the rise in global economy.  Fixed money supply value (in real terms) of goods and services rising ~2% means the purchasing power of one unit of currency would rise ~2%.  So there won't be a scenario where it is growing 10% annually (in real terms) forever.

Also it isn't necessary for currency to exceed the wealth of the world, I don't think that has ever happened.  Right now, global Currency (M0) is ~$5T, even if we use a broader definition of money M1 is something on the order of ~$25T, and M2 is ~$75T.  In comparison (real) Global GDP is ~$75T and the best estimates on global wealth are >$240T.

In this hypothetical scenario a lot depends on how much Bitcoin displaces.  Its closest equivalent is M0 but you can the argument that it would displace a large portion of the money multiplier (or drive it down) and thus the Bitcoin Money supply (in this dubious single currency scenario) might be something on the order of M1.  Still global wealth would be at least a magnitude more.  In other words the global money supply might be 21M BTC but global wealth (in all forms) would be something like 210M BTC.

So in short.  No.

a bit.

1000 bits to a Bitcoin.

Thank you for the offer but it is USD and at US locations only at this time. 

Received requests from two testers.  Need four to six more.

I and another employee have already internally tested the payment method and it worked without issue.  I would like feedback from a variety of people in a variety of locations.  The fee is a third party fee it won't be waived.  I am not asking someone to do something they don't want to already do.  If someone is looking to buy Bitcoins with cash and receive them today here is an opportunity as long as they understand it is a manual process and there may be some rough edges.  For those not interested a polished sales portal will be launching within a week.

Note: This is a beta test of service provider we are considering when we resume operations.  Invoices will be created manually, there may be issues, the cashier may be confused, and it may be a waste of your time.  Please don't offer unless you are willing to participate in a beta test.  If testing is positive this will be rolled out in new sales portal launching in December so if you don't like rough edges but want to pay cash for bitcoins just say tuned.

This is a limited offer for 6-8 individuals today to test a payment providers.  We will probably conduct another test run after the Thanksgiving break and are looking for soft launch of sales portal under the brand name BitSimple in early December.

Terms:
* One sale (max of $500) per person only.
* Each transaction is for $100 to $500.  There is a fee if $3.99 added to the sale amount.
* You will pay cash at any 7-11 store in the United States and receive your coins today (likely within minutes).
* The exchange rate will be MtGox last at the time of your payment.
* Available in USD only, must be located in the US and have a 7-11 location nearby (should be 99% of the US).

If interested send me a PM with the following:
* First & last name.
* Bitcoin address to receive the coins.
* Either an email address (will need printer) and/or mobile phone number (will need a smartphone with internet access).
* Amount of purchase ($100 to $500).

I will manually generate an invoice for you.  The invoice can either be sent by txt message (contains a link) and displayed on a smart phone or sent by email and printed.  If you want I can send it both methods.  You will need to bring the invoice (or your phone with invoice webpage) and cash to any 7-11 store in the United States to make a payment.  Once payment is confirmed (real time) coins will be sent to the address you provided.  Remember at this time it is a manual process but verification and delivery of coins should be fairly quick.  Once again understand this is just a beta test, I am interested in feedback before we launch a sales portal.

There is a secure way to do this. He can provide just an empty private key (or better yet one with a low value).

I work a lot with probabilities so using words like probably, likely, mostly are just a force of habit.  I don't want to presume to know the future.  Maybe Bitcoin would survive a change in minting.  I seriously doubt it but it is possibly (highly unlikely IMHO but possible).

Still even the risk simply isn't worth it.  For a fork to have any chance would require a critical mass of users, merchants, exchanges, service providers, developers, advocates, etc.   The worst possible scenario is two incompatible protocols both calling themselves Bitcoin with significant support behind them.  That is a recipe for disaster.   This is why IMHO there will be no hard forks of the protocol beyond either non-controversial changes or a "we change it or Bitcoin is dead anyways" scenario (crtotographic break of ECDSA or SHA-256).  I certainly won't support them and I feel there are enough pragmatic people which will do the same.

Your net worth measured in tons of gold is unlikely to be more than a fraction.  It hasn't stopped people from buying much smaller gold coins.

All money, all units are arbitrary.  Money has to be scarce or it doesn't work.  
Commodity based money attempts to constrain the supply by a scarce resource.
Fiat based money attempts to constrain the supply based on the whims of a cartel of bankers.
Crypto based money attempts to constrain the supply based on math and logic.

Money is merely an accounting system.  It is a way of keeping score. 


As for why can't we change Bitcoin.  Well the reality is that 42M BTC would work equally well, so would 1000 quintillion BTC.  Bitcoin would probably have worked fine with a fixed money supply (recycling old coin), or a continually inflationary one, or the system we have now however in the long run the difference between 0.5% growth in money supply, 0% growth in money supply, and 0.5% reduction in money supply is really immaterial. 

So if they all could work why not change it?  Well first if they all can work there really is no reason TO change it.  The larger issue is that Bitcoin is a consensus system.  Participation is voluntary.  The rules are known in advance.  This creates a social contract.  People who have chosen to use/adopt/hold Bitcoin have chosen to do so under the premise that the rules won't be changed.  Bitcoin makes it nearly impossible to change the rules and as such rules that don't need to be changed probably never will.  To change the money supply, rate of minting, or the irreversibility of transactions (to include confiscating "lost" coins) is probably impossible.  However if you could it would break the social contract.  It probably would kill Bitcoin.  If you can change one rule you can change them all.  A Bitcoin only has value because people believe they can exchange it for goods, services, or other currencies (either today or in the future).  Breaking the social contract would be a loss of confidence in the entire system and likely a fatal collapse.

Nice.  I broke my personal rule and actually registered to get past the register wall.  The author may be a little to Bitcoin centric.  Personally I don't know if Bitcoin will succeed long term (decades) but I do know the concept of cryptocurrency is here to stay.  Bitcoin has proven it can work.  Maybe Bitcoin remains the ebay of future currencies or maybe it becomes the myspace but the days where cartels of banks create a system that forces the masses to use it has been broken.  It may take a lifetime but like electricity, the personal computer, or the internet it can't be undone.

Every "financial type" (brokers, money managers, banker) should at least look at Bitcoin objectively if for nothing else than to see an alternative.  Look at it with open eyes considering "we may use this or something like it someday". 

This. I am more interested in the shape of the curve.  For a "long time" (in Bitcoin years) the exchange rate growth was something like ~0.5% per day.  Lots of booms and bust along the way but it correlates pretty well to a line with a 0.5% per day slope.  Recently (last two weeks) that has jumped by 20x.  0.5% vs 10% daily that is quite a deviation.  Is this the new normal (we are looking at months or years of 2% per day growth) OR are we looking a regression to the mean scenario (exchange rate eventually falls off to intersect with the 0.5% per day slope)?

I don't know but that is the question.  I would buy at $10, $100, $1,000,  $10,0000, $100,000 the nominal amount if pretty much a non-issue.  If Bitcoin was >$100,000 for a decade and one day "Bitcoin Black Tuesday" there was a "massive" crash from ~$123,000 to $98,000 followed by a quick rebound would you buy?  On the other hand if Bitcoin went up 100% per day for a week would you consider $128,000 to be a good price.

Everything that has ever been bought or sold can be a bubble and not all price increases are a bubble.  One method of identifying the difference is the deviation from historical trends but one has to be aware the trend can change, another is the relative change in volume.

millie or millibit.

That will be 123 millibits, please.
I can't believe the exchange rate is over $10 a millie.

Polls are silly.  There is no central planning committee on Bitcoin units and measures.

If you want to use mBTC, uBTC, or satoshis then go ahead.   A poll isn't going to convince an exchange, merchant, wallet, or service provider to change.  If you want bitstamp to change their orders books to show everything in mBTC then TELL THEM.  Emails, tickets to customer support, etc.

There is no cordination required.  It isn't a puzzle (I know people say that but it is factually wrong).  Each hash is a random guess and miners are looking for a hash below a certain target.   It will take the same number of hashes (in the long run) to solve a block.  Units don't need to work "together", there is no progress towards a solution.  Each hash either instantly "wins" (solves a block) or it is loses and the next hash has no greater chance of being a solution.


Think of hashes like lottery tickets.  In a lottery on average there will be a winner for every x lottery tickets sold.  Sometimes a winner will be found is less than x, sometimes more than x but on average across thousands of lotteries the number of tickets per winner will be roughly x.  If a lottery ticket wins it simply wins, if you buy 1,000 lottery tickets and they are also losers you aren't "closer" to winning next week.  Every ticket has an equal chance of being a winner.  In mining instead of buying lottery tickets your rig is producing hashes but it is the same concept.

It will never happen.  It would require a hard fork and the existing fork will continue to operate.  There would be two mutually incompatible "Bitcoins" operating simultaneously.  Bitcoin is already perfectly divisible if you want simply switch your client to show mBTC.  1 BTC = 1,000 mBTC.  The current Bitcoin fork has 21 billion mBTC.  The exchange rate today is ~$1 per mBTC.