"Decentralization" is a strong argument in favor of the crypto world. It basically means no one will have total control over the public ledger of transactions, hence no one will be able to tamper with it (like spending the same tokens twice, a.k.a. "double spending"). This decentralization is enforced, among other methods, via Proof of Work (PoW) a method which uses computing power to validate transactions. It was the first method used by Bitcoin, but there are other ways to enforce decentralization, like DPoS (the one used on Steemit), or even exotic ones like PoB (Proof of Burn, in which you mine blocks by burning tokens). Like I said, Bitcoin uses PoW, Ethereum uses this and a few hundreds of other tokens (many of them in top 50 are using this).

But computing power can be bought, right? You can even rent it on sites like NiceHash...

So, if someone would want to launch an attack on such a network (known as a 51% attack, see below) how much money should he spend? Well, there is a site which calculated, based on the current hashrate of a few (very) relevant coins, the actual cost of succeeding at a 51% attack.

Before getting into details, here's a short explication of a 51% from the same site:

In Proof of Work (PoW) cryptocurrencies, nodes typically are set up to recognize the blockchain with the most blocks (and therefore the most hashing power) as the correct version of history. Miners with > 50% of the network hashing power can take advantage of this by sending funds to one address on the main chain, while sending the same funds to another address on a forked copy of the blockchain that they are silently mining with more hashing power than the main chain.

Since other nodes only know about the main chain, they will see the first transaction as valid, and exchanges, etc will accept this transaction as valid. This malicious node can later release these silently mined blocks, and other nodes will accept this as the new 'correct chain' since it is longer. This will cause the original transaction to effectively dissappear, and nodes will recognize the funds as being sent to the address from the new chain instead. This is known as a 'double spend' attack.

So, for getting control on Bitcoin, you need half a million worth of computing power to launch a 1 hour 51% attack. In this case, NiceHash only has 2% of the entire computing power, so you can't rent it from there.

But that's not the case of Bytecoin, where the cost is only $981 (yeah, you read that right) and it can definitely be made with rented hashrate from NiceHash.

Here is the complete list of the top 10 cryptos and the theoretical cost of launching a 51% attack, you can see the complete list by clicking the link above.

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It's worth noting also the disclaimer of the site:

This website is intended to bring light to the risk of 51% attacks on smaller cryptocurrencies. It is not intended to encourage or help in completing an attack, but instead to get people talking about the problem and potential solutions.

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I'm a serial entrepreneur, blogger and ultrarunner. You can find me mainly on my blog at Dragos Roua where I write about productivity, business, relationships and running. Here on Steemit you may stay updated by following me @dragosroua.

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