Indeed and being the person who invented the bitcoin mining function I was mildly irritated to be dumped in a newbie section.  I was enjoying USENET flame wars and newbie jokes probably before the average participant of this forum was born   (No slight to other internet-time geriatrics like myself on here).

Anyway rather than post hello and following up to myself 5x I thought I'd say something that was on my mind as irritating about the bitcoin wiki explanation of various things.  I can always re-post it later on.

Adam

ps thanks for the op for another reply

Right thats approximately meaningless.  Now the original or minimal difficulty is 2^32 so 7,673,000 x 2^32 is approx 2^55.  How easy is that in comparison because 7,673,000 ~ 2^23.  (I guess I must've mistranslated it before 55 not 52 bits)

And when you see a bitcoin in hex (like with hashcash because that is what the coin is) you can visually *see* those 55 bits.  This is the latest hash from the block explorer:

http://blockexplorer.com/block/00000000000000e3d3268e05a9901759c1452590d0838a80aeb8abaea59f1e9f

and bingo I can count 0s (14 of them) multiply by 4 (bits per hex nibble) and I know that is a 56bit hashcash collision.  (You get lucky and an extra 1 bit half the time, 2 bits 1/2 time etc).

Adam

To comment on the OP clearly not very environmentally responsible in a direct sense.

According to this article http://www.bloomberg.com/news/2013-04-12/virtual-bitcoin-mining-is-a-real-world-environmental-disaster.html the bitcoin hashcash mining function is taking a gigawatt hours per day.

As the inventor of hashcash thats a lot of power I indirectly caused to be burnt.  Personally I am reasonably green minded so I can see  the negative aspects of that.

However an alternative view is that bitcoin is lower financial transaction costs.  And credit card companies, clearing banks, banks have been getting away with charging some rather high fees.  The cost of that electricity is a lot lower than those fees.  Maybe the money freed up by saving those transaction fees.  Global fund flow is measured in the trillions per day.  Depending on the details banks charge 20 - 50 USD or more and a percent of the amount.  Surely would dwarf current mining costs.  Human resources have value too - if banking become more efficient and if people can save money, human resources are freed to invest in and work on more human progress.  Maybe we get fusion power a year sooner, or people can buy more solar with the money saved etc. in the big picture.  Also about half the bitcoins have already been mined.  Though I dont think the mining arms race is barely started.  I think its probable we will see rows of datacenter racks full of 22nm custom chips ultra dense blades in datacenters chasing down the last of it.  ie right at the technology limit tracking moore's law.

Adam

Hi

Digging myself out of the newbie jail. But a real question - why is difficulty not expressed in bits?

With hashcash I always used eg 20bits.  I think bitcoin is currently at 52.  As bitcoin mining is hashcash mining plus an extension to allow fractional bits (rather than to find k 0 bits, to find a number < 2^k where can be fractional). 

But its hard to be 100% certain if I even correctly converted that because this page is unnecessarily complex for a very simple actual problem: https://en.bitcoin.it/wiki/Difficulty

and bits are very easy to read.  If one looks at the hash output in hex just multiply the leading 0s by 4 (and the next nibble figure out if it is >7 = 4 bits, > 3 = 3 bits, > 1 = 2 bits and 1 = 1 bit (and obviously 0 would be another leading 0).  QED trivial, human comprehensible difficulty that can be handchecked.  That was part of the design aim for hashcash to simplify the computational, programming and human verification.

Adam