Are Bitcoin Block Hashes Predictable


Bitcoin uses two rounds of SHA256 on the entire contents of each block (which includes a reference to the previous block) as well as a randomly varied nonce. When the result of those calculations are below a network-determined threshold it is considered to be a valid solution. These solutions are published along with the block as it is distributed to the network so finding the hash of old blocks is trivially easy, you just look them up. Verifying that the math was done correctly and that the result meets the criteria requires only a single iteration of sha256(sha256(block+nonce)) while finding the appropriate nonce the first time takes an absolutely insane number of attempts.

The insane number of attempts is necessarily because the output of sha256 is, effectively, pseudorandom and covers a huge space. The algorithm is deterministic, so sha256(x) will always have the same result, but the result is entirely unpredictable and minor changes in the value of x will dramatically...

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When it's used as it's intended to, the nonce usually begins at a certain point and increments from there. This can restart every second, since there is a second-specific timestamp in the block, but modern ASICs can do far more than 2^32 hashes per second, so it seems reasonable that nonces should be distributed fairly evenly.

may a miner force a mined block to have a specific nonce? (if his hashrate allows him to)

Yes. He'd do this by fixing his block header's nonce and changing transactions instead (the coinbase transaction, a.k.a. block reward, is a perfect place for this); by changing any transaction, the Merkle root in the block header will change.

The usual mining loop only takes two SHA256 hashes per attempt. If you only include the coinbase transaction in your block, this will add (at least; I'm unsure if it'd have to fill out 1 to be an even number, as it does for 3) two SHA256 hashes per attempt, meaning you'd be (at least) twice as slow as normal....

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Instructions on how to use the Bitcoin Mining Calculator:

Enter the hash rate of the Bitcoin miner you’re planning to use Click on “Calculate mining revenue” That’s it! (we said it was simple….)

Note: If some values in the Bitcoin mining calculator don’t seem right (exchange rate, block reward, etc.) you can adjust them manually. However normally they are all up to date.

Keep in mind that:

Revenue is shown in USD based on the current exchange rate, the exchange rate can (and probably will) change from time to time. Revenue is based on current difficulty to mine Bitcoins. Difficulty can (and probably will) change. From past experience it usually goes up as time goes by. Revenue IS NOT profit. You still have to take into account the cost of your mining hardware and the electricity to run it (and cool it down if needed).

If you want to know more about Bitcoin mining profitability check out this page.

Bitcoin mining secures the Bitcoin network. Without...

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Bitcoin’s mining difficulty increased by 16.6 percent over the weekend, signaling that the network’s overall hash rate has also increased by a similar amount over the past two weeks. The network’s total estimated hash rate has essentially doubled since the middle of October. A large chunk of this increase has taken place over the past month, where the hash rate has increased by more than 50 percent.

The network hash rate is the total amount of computing power pointed at the Bitcoin network.

Pools That Saw Their Share of Total Hashing Power Increase

It’s difficult to know where exactly this new hashing power is being deployed, but it is possible to see the differences in mining pools’ shares of the overall hash rate.

When comparing the most recently completed difficulty period with a run of 2016 blocks from the middle of October, GBMiners is the pool that saw the largest amount of growth. GBMiners enjoyed an increase of 62 blocks compared to the...

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I tried to break it down to someone yesterday. It went like this: BitCoin is a digital Internet currency. Think of it as an counterfeit-proof electronic dollar which is not manipulated by a central authority such as the Federal Reserve. It’s a basis of trade for goods, just as any other currency. Value is based on scarcity, and new BitCoins are only minted at a predictable rate once a Block is solved…

The BitCoin currency is a peer-to-peer solution for the problems which are seen in any system of currency. Every BitCoin transaction is recorded in a public ledger, which is found at Block Explorer. Each transaction is hashed into a block, the specifics of which I don’t want to get into, but are explained in the original paper Bitcoin: A Peer-to-Peer Electronic Cash System by BitCoin creator Satoshi Nakamoto. After the solution to the block is found, it is replicated throughout the peer-to-peer network, and all transactions are then verified by the BitCoin client software,...

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Hash (not to be confused with hashtags or hashish which are other things entirely) is data that was derived through a one way mathematical function.

For example hashing the sentence "the quick brown fox jumps over the lazy dog" with the popular MD5 hash function yields 1e280e1713df124d35709cf6138d9f91 (hashes are usually shown in hex format (base 16) rather than binary to save space), but if we make just a tiny change to the input, such as using a capital "T" instead of lower-case, the hash is 37c4b87edffc5d198ff5a185cee7ee09 - almost completely different, but always exactly the same size.

The idea is to map input data (a file, password, etc.) into fixed size output data. With only the output data the input cannot be derived.

For a simple way to think of this: remainder functions have a similar mechanism. If one has the remainder 1 from dividing 7 by 3 no one can determine what the inputs where because other functions provide the same result. Seven divided by...

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That the block chain cannot be easily forked represents one of the central security mechanisms of Bitcoin. Given the choice between two block chains, a Bitcoin miner always chooses the longer one - that is to say, the one with the more complex hash. Thusly, it ensures that each user can only spend their bitcoins once, and that no user gets ripped off.

As a consequence of the block chain structure, there may at any time be many different sub-branches, and the possibility always exists of a transaction being over-written by the longest branch, if it has been recorded in a shorter one. The older a transaction is though, the lower its chances of being over-written, and the higher of becoming permanent. Although the block chain prevents one from spending more Bitcoins than one has, it means that transactions can be accidentally nullified.

A new block chain would leave the network...

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What is bitcoin difficulty?

Bitcoin difficulty is an estimate about how difficult it is to mine (find) a new bitcoin block. Bitcoin mining has two main purposes. One is adding transactions to the bitcoin block chain. The other purpose is to create new bitcoins.

The total number of bitcoins that will ever be mined is limited to 21 million. Moreover, the bitcoin protocol determines a time horizon over which the bitcoins will be created. This is done to limit the supply of bitcoins. A new block is mined every 10 minutes. The number of bitcoins in one block is currently BTC 25 and is halved every 210,000 blocks or approximately every four years.

If everybody could easily mine new bitcoins, inflation would be the result. Bitcoin difficulty exists to ensure a limited bitcoin supply. This does not mean there could be no inflation for bitcoin. Activities like bitcoin lending can increase the bitcoin money supply. But the main...

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Bitcoin is the currency of the Internet: a distributed, worldwide, decentralized digital money. Unlike traditional currencies such as dollars, bitcoins are issued and managed without any central authority whatsoever: there is no government, company, or bank in charge of Bitcoin. As such, it is more resistant to wild inflation and corrupt banks. With Bitcoin, you can be your own bank.

If you are new to Bitcoin, check out We Use Coins and You can also explore the Bitcoin Wiki:

How to buy bitcoins worldwide
Buying Reddit Gold with bitcoin

Will I earn money by mining bitcoin?

Security guide for beginners - (WIP)

Community guidelines

Do not use URL shortening services: always submit the real link. Begging/asking for bitcoins is absolutely not allowed, no matter how badly you need the bitcoins. Only requests for donations to large, recognized charities are allowed, and only if there is good reason to believe that the person...
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In this overview, you’ll learn how the Bitcoin system works in general and what terminology we use to describe each part. This is recommended reading for anyone who is new to Bitcoin development. If you’ve been around for awhile, you can probably just skim it or skip it altogether.

In addition to this overview, we highly recommend reading Satoshi Nakamoto’s original high-level description of the Bitcoin system, published in 2008.


We’ll refer often to 21, which is designed to provide everything you need to follow the tutorials on, including a technology that lets you receive a steady stream of satoshis (fractional bitcoins) for use in creating actual transactions that will appear on the blockchain.


One of the most frequently used data types in Bitcoin is a cryptographic hash. (We’ll simply call them “hashes” from this point on, but you should be aware that there are non-cryptographic hashes that don’t have the same...

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Anyone with an interest in bitcoin will have heard the phrase 'cryptographic hash function' at some time or other. But what exactly does it mean, and how is it connected to cryptocurrency?

Hash functions are an essential part of, not only of the bitcoin protocol, but of information security as a whole.

In the following article we'll take a look at some simple examples of how they work, with a simple demonstration, too.

What's a hash function?

In the abstract, a hash function is a mathematical process that takes input data of any size, performs an operation on it, and returns output data of a fixed size.

In a more concrete example, this can be used to take a sequence of letters of any length as input – what we call a string – and return a sequence of letters of a fixed length. Whether the input string is a single letter, a word, a sentence, or an entire novel, the output – called the digest – will always be the same length.

A common use of...

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The best way to think about Bitcoin difficulty is to view it as the maximum amount of computing power it will take to find a particular block reward. The difficulty number is what helps keep the Bitcoin block time at around ten minutes. As more hashing power is added to the network from different computers around the world, the difficulty of finding a block needs to be adjusted accordingly. If there was no mechanism for regulating the amount of hashing power it will take to mine a particular block, then it would be impossible to effectively secure the blockchain.

How is Bitcoin Difficulty Regulated?

The difficulty of mining a particular Bitcoin block changes over time to make sure that it does not become too easy or too difficult to mine bitcoins. As more hashing power is added to the Bitcoin network, it becomes more difficult to mine bitcoins. Bitcoin difficulty is recalculated every 2016 blocks, which usually turns out to be roughly every two weeks. After every...

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Bitcoin is a modern enigma. Created by an anonymous programmer who called himself (or herself) Satoshi Nakamoto this virtual currency began circulating on the Internet in 2009 and has since attracted both praise and derision for either being the answer to all the evils typically associated with money or for being the world’s most elaborate Ponzi scheme. This is largely because Bitcoin is not your typical currency. There’s no carrying bitcoins around in one’s pocket, no using them in ticket machines on the Tube. Nor are they regulated by a central bank or subject to monetary policy. They exist only because people agree they do, as binary code, in cyberspace.

The Serious Business of Making Bitcoins

All conversations regarding the virtual currency known as Bitcoin inevitably come around to questions of origin. Where do they come from? How do I get them? Because there is no central bank with the power and authority to mint new bitcoins at will there has to be some other...

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If you’ve already heard about Bitcoin, you probably know that mining is one of the core concept underlying this blockchain technology. You’ve maybe also heard that mining involves thousands of powerful computers which solve some magical puzzles. But do you really know how does mining works under the hood?

Science behind Bitcoin

Despite the fact that the blockchain technology takes advantage of a few sophisticated numerical algorithms, the underlying concepts are quite straightforward. And definitely you don’t need an engineering degree in programming to grasp the gist of this revolutionary technology!

Cryptographic hash function

Hash functions belong to a very useful class of algorithms that transform any data into a short message which then we can easily compare and process. Simple example of that could be a mathematical function which as an output gives the remainder of division by 1000 (modulo operation). You can think about hashes as fingerprints...

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Recently over dinner, I was asked to explain bitcoin mining, and I struggled as it is entangled with a number of other concepts. Here’s my attempt at breaking it down into bite-sized pieces.

What is bitcoin mining?

Mining is the process of writing pages (blocks) of bitcoin transactions into the bitcoin ledger, called ‘The Bitcoin Blockchain’, and getting rewarded with newly created bitcoins.

To understand this in more detail, the rest of the post describes:

How do bitcoin transactions work? Why is mining needed in bitcoin? Why do miners mine? What is this ‘computationally expensive’ guessing game? Why pay rewards in BTC instead of USD? Who mines? What can and can’t miscreants do?

If you are new to bitcoin, it might be worth having a quick read of “A gentle introduction to bitcoin”.

How do bitcoin transactions work?

The process is:

Make a payment (a bitcoin transaction) Wait for it to be mined in a block (average 10 mins) Wait for more...
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This article explains Bitcoin mining in details, right down to the hex data and network traffic. If you've ever wondered what really happens in Bitcoin mining, you've come to the right place. My previous article,

Bitcoins the hard way

described how I manually created a Bitcoin transaction and sent it into the system. In this article, I show what happens next: how a transaction gets mined into a block.

The purpose of mining

Bitcoin mining is often thought of as the way to create new bitcoins. But that's really just a secondary purpose. The primary importance of mining is to ensure that all participants have a consistent view of the Bitcoin data. Because Bitcoin is a distributed peer-to-peer system, there is no central database that keeps track of who owns bitcoins. Instead, the log of all transactions is distributed across the network.

The main problem with a distributed transaction log is how to avoid inconsistencies that could allow someone to spend...

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This is part 3 of my series of blog posts on the topic cryptocurrencies. The first, introductory part can be found here. The second part on mining can be found here.

Recap – Bitcoin = direct electronic transactions without intermediary

To recap, I explained the main idea behind the Bitcoin protocol, which allows electronic peer-to-peer transactions without an intermediary. In brief, the process works as follows:

I own a certain amount of Bitcoin. This can be publicly verified, because every Bitcoin transaction since the very first one is entered into a public ledger called the block chain. So I can’t pretend to have more money than I have. I can send a certain amount of Bitcoin to a recipient, and I can’t cheat while doing that, because the transaction is publicly broadcast to all nodes in the network. I could simultaneously send out more Bitcoins than I have, but the network decides through a process that is a bit like voting (and in reality involves solving a...
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There are two things you need to do:

Download a bitcoin wallet

Create a pool account

Set up paymentSet up workers

Download a Bitcoin Wallet

A wallet is a program that sits on your computer and gives you a wallet address, this is a unique string of numbers and letters that you will use to receive bitcoins. Download the client for your computer from

After installation, you will have to save a file called wallet.dat, keep this file safe, as this contains your unique wallet address within it, including all bitcoins that you will gain. If you lose this file, you cannot recover any bitcoins it contained.

Create a Pool Account Once you have a wallet address, create a pool account. A pool is a huge collection of other people working towards gaining bitcoins. Due to the complexity of mining a bitcoin, it has become unrealistic to solo mine–the act of processing millions of numbers to solve the block...

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