The argument that Bitcoin has a very high energy requirement and is therefore harmful to the environment persists. So that for the crypto currency is higher than the consumption of some countries. Environmentalists clap their hands over their heads in dismay.

The Proof of Work as a Mechanism to Consensus – A Web Flaw in Bitcoin or One of Its Greatest Strengths?

## Trustless Consensus: Proof of Work

The Proof of Work (POW) is at the heart of what Satoshi Nakamoto proposedSystems. It ensures the integrity and immutability of the network. The miner’s task is to select transactions from the network (the so-called mem pool), to create a so-called canditate block from them and then to create a root hash by counting up a so-called nonce, which starts with a certain number of 0-bits .

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In plain language this means: In order for a block containing transactions to be viewed as correct by the Bitcoin network, it must meet certain criteria. On the one hand, it must contain the root hash of the previous block. On the other hand, its own root hash must begin with a certain number of zeros (0 bits). Basically, the higher the number of 0 bits, the more difficult the block is to mine.

## Root hashes, difficulty and energy consumption in Bitcoin

The root hash is the result when all data contained in the block – the transactions, the block number, the root hash of the predecessor, nonce and so on – are encrypted („hasht“) with an SHA-256 function. This creates a completely random sequence of letters and numbers. The special thing about a hash function is that a completely new output results for every change in the input. That is why the nonce exists as a variable in a candiate block. By counting up the nonce, you always create a completely new root hash that may meet the requirements of the network.

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The difficulty changes depending on the computing power of all participants in the network. Every 2016 blocks the difficulty adapts to this performance, so that the network finds a new block every 10 minutes on average. The difficulty indicates how many 0-bits must appear at the beginning of a root hash.

For example, the root hash for a block looks like this:

If the root hash meets the criterion of 0 bits, which in turn is defined by the difficulty of the network, all miners recognize this block as valid, insert it into their locally stored version of the blockchain and use it as the basis for calculating the next root Hashes. Such a hash can only be found by guessing – and this guessing costs computing power and consequently energy. The chain (blockchain) with the most accumulated proofs of work is viewed by the network as the „true“ chain.

In short: the POW represents verifiably energy output.