Technical Background more »
During mining, your computer runs a cryptographic hashing function (two rounds of SHA256) on what is called a block header . For each new hash, the mining software will use a different number as the random element of the block header, this number is called the nonce . Depending on the nonce and what else is in the block the hashing function will yield a hash which looks like this:
You can look at this hash as a really long number. (It's a hexadecimal number, meaning the letters A-F are the digits 10-15.) Now to make mining difficult, there is what's called a difficulty target . To create a valid block your miner has to find a hash that is below the difficulty target. So if for example the difficulty target is 1000000000000000000000000000000000000000000000000000000000000000, any number that starts with a zero would be below the target, e.g.:
If we lower the target to 0100000000000000000000000000000000000000000000000000000000000000, we now need two zeros in the beginning to be under it:
Because the target is such an unwieldy number with tons of digits, people generally use a simpler number to express the current target. This number is called the mining difficulty . The mining difficulty expresses how much harder the current block is to generate compared to the first block. So a difficulty of 70000 means to generate the current block you have to do 70000 times more work than Satoshi had to do generating the first block. Though be fair though, back then mining was a lot slower and less optimized.
The difficulty changes every 2016 blocks. The network tries to change it such that 2016 blocks at the current global network processing power take about 14 days. That's why, when the network power rises, the difficulty rises as well.
Bitcoin Mining Hardware
CPU's: In the beginning, mining with a CPU was the only way to mine bitcoins. Mining this way via the original Satoshi client is how the bitcoin network started. This method is no longer viable now that the network difficulty level is so high. You might mine for years and years without earning a single coin.
GPU's: Soon it was discovered that high end graphics cards were much more efficient at bitcoin mining and the landscape changed. CPU bitcoin mining gave way to the GPU (Graphical Processing Unit). The massively parallel nature of some GPUs allowed for a 50x to 100x increase in bitcoin mining power while using far less power per unit of work. While any modern GPU can be used to mine, the AMD line of GPU architecture turned out to be far superior to the nVidia architecture for mining bitcoins and the ATI Radeon HD 5870 turned out to be the most cost effective choice at the time.
FPGA's: As with the CPU to GPU transition, the bitcoin mining world progressed up the technology food chain to the Field Programmable Gate Array. With the successful launch of the Butterfly Labs FPGA ‘Single', the bitcoin mining hardware landscape gave way to specially manufactured hardware dedicated to mining bitcoins. While the FPGAs didn't enjoy a 50x - 100x increase in mining speed as was seen with the transition from CPUs to GPUs, they provided a benefit through power efficiency and ease of use. A typical 600 MH/s graphics card consumed upwards of 400w of power, whereas a typical FPGA mining device would provide a hashrate of 826 MH/s at 80w of power. That 5x improvement allowed the first large bitcoin mining farms to be constructed at an operational profit. The bitcoin mining industry was born.
ASIC's: The bitcoin mining world is now solidly in the Application Specific Integrated Circuit (ASIC) era. An ASIC is a chip designed specifically to do one thing and one thing only. Unlike FPGA's, an ASIC cannot be repurposed to perform other tasks. An ASIC designed to mine bitcoins can only mine bitcoins and will only ever mine bitcoins. The inflexibility of an ASIC is offset by the fact that it offers a 100x increase in hashing power while reducing power consumption compared to all the previous technologies. For example, a good bitcoin miner like the Monarch from Butterfly Labs provides 600 GH/s (1 Gigahash is 1000 Megahash. 1 GH/s = 1000 MH/s) while consuming 350w of power. Compared to the GPU era, this is an increase in hashrate and power savings of nearly 300x. (Calculate the earnings of any bitcoin mining hardware device using this bitcoin mining calculator ).
Unlike all the previous generations of hardware preceding ASIC, ASIC is the "end of the line" when it comes to disruptive technology. CPUs were replaced by GPUs which were in turn replaced by FPGAs which were replaced by ASICs. There is nothing to replace ASICs now or even in the immediate future. There will be stepwise refinement of the ASIC products and increases in efficiency, but nothing will offer the 50x - 100x increase in hashing power or 7x reduction in power usage that moves from previous technologies offered. This makes power consumption on an ASIC device the single most important factor of any ASIC product, as the expected useful lifetime of an ASIC mining device is longer than the entire history of bitcoin mining. It is conceivable that an ASIC device purchased today would still be mining in two years if the device is power efficient enough and the cost of electricity does not exceed it's output. Mining profitability is also dictated by the exchange rate, but under all circumstances the more power effecient the mining device, the more profitable it is.
Software
There are two basic ways to mine: On your own or as part of a pool. Almost all miners choose to mine on a pool because it takes the luck out of the process. Before you join a pool, make sure you have a bitcoin wallet so you have a place to store your bitcoins. Next you need to join a mining pool like Eclipse. Eligius or BTC Guild. With pool mining, the profit from any block a member generates is divided up among the members of the pool. This gives the pool members a more frequent, steady payout (this is called reducing your variance), but your payout(s) will be less unless you use a zero fee pool like Eclipse. Solo mining will give you large, infrequent payouts and pooled mining will give you small, frequent payouts, but both add up to the same amount if you're using a zero fee pool.
Once you have your client set up or you have registered with a pool, the next step is to set up the actual mining software. The most popular GPU/FPGA/ASIC miner at the moment is BFGminer or CGminer. For a full GUI experience, try EasyMiner .
If you want a quick taste of mining without installing any software, try Bitcoin Plus. a browser-based CPU Bitcoin miner. As a CPU miner it's not cost-efficient for serious mining, but it does illustrate the principle of pooled mining very well.
Thanks to:
Blitzboom and the guys from #bitcoin-dev for their help with writing the guide!
Quick updates
02.02.2014
Datacenter connectivity issues have caused short drop in the hashrate. The problem has been resolved and all stratum servers are now reachable. This all happened when 900 Th/s was within a reach. We will get there again with your support and participation in mining ;-)
17.01.2014
We were having an extremely lucky yesterday's mining session. Unfortunately, around 1.30 AM UTC, we were experiencing stratum server issues that eventually spread across all our stratum servers. The problem has been resolved now and mining continues.
13.01.2014
The pool database backend has been successfully migrated to a new hardware. The website is now fully operational. The whole migration process has been accomplished without interrupting the actual mining.
13.01.2014
We are currently migrating pool database to a new machine. Mining will continue without interruption, only website will be down for 1-2 hours.
18.12.2013
Some recent payouts didn't go thru bitcoin network because of unsatisfied transaction fees. We're finding a soluton and all payouts will be processed soon
16.10.2013
In recent days we experienced some successful thefts of user's funds using compromised email accounts. We strongly encourage all users to change email passwords. There's no reason to think that pool security itself has been compromised.
08.07.2013
Getwork protocol support ended. Please be sure your miners support Stratum protocol. You can still use your old getwork miners with Stratum proxy installed on your mining rig.
21.05.2013
Bug in bitcoind caused many invalid blocks generated in recent hours. Thanks to cooperation with bitcoin developers, a bugfix has been deployed. Pool is now back in normal operation.
26.04.2013
Because the user database has been compromised in recent hack, please change password to your pool account!
25.04.2013
Pool is recovering to normal operation from previous attack. delayed payouts will be processed in the afternoon (UTC).
18.04.2013
Pool is recovering from DDoS attack.
14.04.2013
As announced in Getwork deprecation plan. the hashrate on Stratum is far above 90%, so workers which are still using the deprecated Getwork protocol are now charged by 10% fee. Please update your software and start using modern Stratum miners to reduce your fees back to 2%!
12.03.2013
Bitcoin network recently experienced global problems which caused some pool blocks to be invalid. Everything seems to be fixed now.
10.03.2013
Default mining URL for Stratum is stratum.bitcoin.cz:3333 . If you're still using api.bitcoin.cz, please fix your URL to prevent fallback to deprecated Getwork protocol.
08.03.2013
Stratum proxy version 1.5.2 has been released. This is bugfix release which add compatibility with some old miners (phoenix, Diablo).
03.03.2013
Stratum proxy version 1.5.0 has been released. All proxy users are encouraged to update .
13.02.2013
ASIC mining become a reality. Jeff Garzik (bitcoin core developer) is testing first shipped unit of Avalon ASIC miner on our pool.
30.01.2013
Native IPv6 address is now available. You can use ipv6.stratum.bitcoin.cz:3333 in your miner if your miners have IPv6 support! Please note that IPv6 works only for Stratum miners.
08.12.2012
If you're using old miners from early 2011 or you're mining on URL "mining.bitcoin.cz:8332", please update your miners and use "api.bitcoin.cz:8332" in your configuration instead. Mining on URL "mining.bitcoin.cz" is not working anymore.
27.11.2012
Only one day remains to halving block reward from 50 BTC to 25 BTC. Thanks to this change in Bitcoin world, mining income will be drastically reduced. As a countermeasure, pool is now paying block fees to miners. Everything you need to collect block fees is to use miner with Stratum support .
24.11.2012
Pool is now giving transaction fees to Stratum miners! Use miner with Stratum support (latest version of GUIminer, cgminer, bfgminer, poclbm) or use your favourite miner with Stratum proxy to improve your mining income!
19.11.2012
Guiminer with Stratum support has been released. Upgrade is highly recommended.
12.10.2012
Manni's GPU Bitcoin Mining Rig Farm 16GH s
All users are encouraged to install or update Stratum proxy to current stable version 1.1.1. Instructions are here .
12.10.2012
New version of cgminer has been released. Please update cgminer to version 2.8.3 . which fixes serious bugs introduced in previous versions.
10.10.2012
In effect from 01.11.2012, pool increases the lower limit for payouts ("send threshold") to 0.05 BTC (around $0.6) as a protection against high transaction fees for tiny payouts. If you have a balance of less than 0.05 BTC and want to withdraw them, please do so before November 1.
20.09.2012
New version of poclbm miner has been released. All poclbm users are encouraged to update their miner, latest version includes major optimization.
11.09.2012
I'm seeking for beta testers of new mining protocol called Stratum mining. If you want to join testing, please download the proxy and point your miners to it. Thank you!
08.07.2012
Do you have some bitcoins from the mining and do you want to sell them for cheap? Add your offer to localbitcoins.com and find a buyer in your neighborhood!
11.06.2012
Follow pool's page for recent updates and news!
05.02.2012
poclbm/GUI miner is affected by serious bug. If your miner is crashing on 'unexpected error' message, please follow miner forums for the newest versions.
26.01.2012
Pool is now supporting BIP 16 protocol extension, as described here. It is just internal change on the Bitcoin network, miners don't need to update anything.
08.11.2011
Implemented prioritization of long polling. Fast miners should expect lower stale ratio.
10.10.2011
Merged mining for Namecoins added. Please fill NMC address on your profile to start collecting Namecoins! Accounting isn't finished yet, but will come very soon.
03.10.2011
Bitcoin.cz is official sponsor of European Bitcoin conference 2011. See you on 25.-27. November in Prague!
26.03.2011
Second server added
Total hashrate at 60Ghash/s
19.01.2011
We're over 20 Ghash/s
20.12.2010
Bitcoin Currency and GPU Mining Performance Comparison
What is a Bitcoin?
This article looking at Bitcoins and the performance of various GPUs with mining them was really a big team effort at PC Perspective. Props goes out to Tim Verry for doing the research on the process of mining and helping to explain what Bitcoins are all about. Ken Addison did a great job doing through an alottment of graphics cards running our GUIMiner and getting the data you will see presented later. Scott Michaud helped with some graphics and imagery and I'm the monkey that just puts it all together at the end.
** Update 7/13/11 ** We recently wrote another piece on the cost of the power to run our Bitcoin mining operations used in this performance article. Based on the individual prices of electric in all 50 states of the US, we found that the cost of the power to run some cards exceeded the value of the Bitcoin currency based on today's exchange rates. I would highly recommend you check out that story as well after giving this performance-based article a thorough reading. ** End Update **
A new virtual currency called Bitcoin has been receiving a great deal of news fanfare, criticism and user adoption. The so called cryptographic currency uses strong encryption methods to eliminate the need for trust when buying and selling goods over the Internet in addition to a peer-to-peer distributed timestamp server that maintains a public record of every transaction to prevent double spending of the electronic currency. The aspect of Bitcoin that has caused the most criticism and recent large rise in growth lies in is its inherent ability to anonymize the real life identities of users (though the transactions themselves are public) and the ability to make money by supporting the Bitcoin network in verifying pending transactions through a process called “mining” respectively. Privacy, security, cutting out the middle man and making it easy for users to do small casual transactions without fees as well as the ability to be rewarded for helping to secure the network by mining are all selling points (pun intended) of the currency.
When dealing with a more traditional and physical local currency, there is a need to for both parties to trust the currency but not much need to trust each other as handing over cash is fairly straightforward. One does not need to trust the other person as much as if it were a check which could bounce. Once it has changed hands, the buyer can not go and spend that money elsewhere as it is physically gone. Transactions over the Internet; however, greatly reduce the convenience of that local currency, and due to the series of tubes’ inability to carry cash through the pipes, services like Paypal as well as credit cards and checks are likely to be used in its place. While these replacements are convenient, they also are much riskier than cash as fraudulent charge-backs and disputes are likely to occur, leaving the seller in a bad position. Due to this risk, sellers have to factor a certain percentage of expected fraud into their prices in addition to collecting as much personally identifiable information as possible. Bitcoin seeks to remedy these risks by bringing the convenience of a local currency to the virtual plane with irreversible transactions, a public record of all transactions, and the ability to trust strong cryptography instead of the need for trusting people.
There are a number of security measures inherent in the Bitcoin protocol that assist with these security goals. Foremost, bitcoin uses strong public and private key cryptography to secure coins to a user. Money is handled by a bitcoin wallet, which is a program such as the official bitcoin client that creates public/private key pairs that allow you to send and receive money. You are further able to generate new receiving addresses whenever you want within the client. The wallet.dat file is the record of all your key pairs and thus your bitcoins and contains 100 address/key pairs (though you are able to generate new ones beyond that). Then, to send money one only needs to sign the bitcoin with their private key and send it to the recipient’s public key. This creates a chain of transactions that are secured by these public and private key pairs from person to person. Unfortunately this cryptography alone is not able to prevent double spending, meaning that Person A could sign the bitcoin with his private key to Person B, but also could do the same to Person C and so on. This issue is where the peer-to-peer and distributed computing aspect of the bitcoin protocol come into play. By using a peer-to-peer distributed timestamp server, the bitcoin protocol creates a public record of every transaction that prevents double spending of bitcoins. Once the bitcoin has been signed to a public key (receiving address) with the user’s private key, and the network confirms this transaction the bitcoins can no longer be spent by Person A as the network has confirmed that the coin belongs to Person B now, and they are the only ones that can spend it using their private key.
The privacy and anonymity afforded by the bitcoin protocol has received flak recently due to the currency being used to purchase illegal drugs and other products online. The US government has seen a number of members speak out against the currency because of the illegal drug involvement and taxation implications. However, bitcoin is not the only currency that is used by a number of people for illegal uses, and it is certainly not representative of a majority of illegal usage. Regardless of the relatively small number of illegal uses, the privacy afforded by bitcoin is not inherently a bad thing. As the Internet equivalent to a local currency such as cash, bitcoin is able to facilitate a much higher level of anonymity than other currencies used online. The privacy implications are not only good for those mis-using it for nefarious purposes; it is actually a good thing for legal transactions because sellers do not need to collect nearly as much personally identifiable information in order to trust the buyer enough to go through with the sale. Traditionally, telephone numbers, addresses, financial information, and other personal information has been required in order for even the most mundane transactions over the Internet as sellers needed to protect themselves as much as possible from fraud.
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