Show how difficult it is to find new bitcoin blocks on a simplified example.
Objective of the game is to find integer that will lead to lowest possible double-SHA256 hash when integer is appended to string Bitcoin.
You can try it interactively on the main page for Bitcoin by choosing any number. You will immediately see corresponding hash and how good it is.
Trying it manually is however very inefficient. If you want to get better results faster, you will need to develop a program that will do the hashing for you at much faster speed.
Check download page for sample scripts.
Bitcoin hashing is a fundamental process in the Bitcoin network, central to how transactions are verified and new blocks are added to the blockchain. It relies on a cryptographic hash function called SHA-256 (Secure Hash Algorithm 256-bit), which takes an input of any size and produces a fixed-size output—a 256-bit (32-byte) hash that appears as a seemingly random string of characters. In Bitcoin mining, hashing is used to solve a computational puzzle: miners compete to find a hash that meets a specific condition, which requires adjusting an input value called a nonce. Let’s break this down step-by-step and use "Bitcoin" as the word to be hashed with some example nonces to illustrate.
The process begins with a block of data, which includes the block header. The block header contains several components: the previous block’s hash, a timestamp, the Merkle root (a summary of all transactions in the block), the difficulty target, and the nonce—a 32-bit number that miners tweak. For simplicity, let’s imagine we’re hashing just the word "Bitcoin" combined with a nonce, though in reality, the full block header is hashed. The SHA-256 algorithm processes this input twice and outputs a unique hash. The goal in Bitcoin mining is to find a nonce that, when hashed with the rest of the block data, produces a hash with a certain number of leading zeros, determined by the network’s difficulty level.
Let’s try an example. Suppose we start with the input "Bitcoin" concatenated with a nonce of 1, so the full input is "Bitcoin1". Feeding "Bitcoin1" into SHA-256 gives us a hash like this: c4947f079b4469188966946828776b86ee03d5f09d846b5285daea1c2b9b4ef7. Now, imagine the Bitcoin network requires a hash with at least six leading zeros, say 000000.... Our result doesn’t meet this criterion, so we’d adjust the nonce and try again.
Let’s increment the nonce to 2, making the input "Bitcoin2". Hashing this with SHA-256 results in: 017bcdedc96716ff44836961e5c76dc768d069fbd4bf61a068628f12302f5900. Only one leading zero and we need at least six. The key property of SHA-256 is that even a tiny change in the input—like increasing the nonce by 1—produces a completely different, unpredictable hash. This is why miners must brute-force the process, trying millions or billions of nonces.
Finally, let’s suppose after many attempts we try nonce 2894985, so "Bitcoin2894985". Hashing this gives us: 000000147a9a353accc9ccbc9ec969935de9ecf1f772716e7725a6f122f6b7b4 . Bingo! This hash starts with 000000, meeting our hypothetical six-zero requirement. In Bitcoin, the difficulty adjusts dynamically, often requiring many more leading zeros (19 leading zeroes are required as of March 2025), which is why miners use specialized hardware like ASICs to perform trillions of hashes per second. Once a valid hash is found, the miner broadcasts the block with the winning nonce, and the network verifies it by re-hashing the data. If it checks out, the block is added to the blockchain, and the miner earns a reward.
This trial-and-error process secures Bitcoin by making it computationally expensive to add blocks, deterring malicious actors from altering the blockchain—any change would require re-mining all subsequent blocks faster than the honest network can mine new ones. The nonce, though simple, is the key variable miners manipulate, and the unpredictability of SHA-256 ensures that hashing remains a game of persistence and power. Using "Bitcoin" with random nonces like 1, 2, or 2894985 shows how drastically the output changes, highlighting the beauty and brute force of this system.