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The astounding rise of Bitcoins’ value led to a wave of discussion about the merits, the dangers and the future of cryptocurrencies. Most articles in mainstream media focus on its financial aspects, whether Bitcoins produce social value or if they are yet another speculative bubble. The technology behind it receives much less attention, apart from a rapid mention: “Blockchains, descentral run ledgers, power Bitcoins transactions…” But behind this simplified description there stands a complex environment, baffling to lay people and even tech-savvy individuals alike.
Forks you won’t eat with.
Blockchain technology is the physical representation of the everlasting battle betwenn central and decentral systems. At the moment it enables a decentral system of self-regulated ledgers, into which all transactions are recorded and transparent to all participants: much like if we all carried a little paper with us, which told who owned whom what, since when. These little papers are what is called smart contracts. A bundle of such transactions forms a block and with each new block we finally have the blockchain.
Although smart contracts can be used for a number of different use cases, their uses are not always obvious, because the general talk is about “the Bitcoin”, as if it was the one use it has, a misleading proposition. Bitcoin is a blockchain whose sole transaction capacity is the monetary one. Ethereum, on the other hand, enables more complex smart contracts. Much like this difference between bitcoins and ethereum, other coins and blockchains are popping up with a number of new features.
Blockchain technology and the smart contracts it supports are at the end of the day code. It is like saying that every link of the chain is minted the moment someone needs it. Perhaps someone wants to mint it with brass, while another person uses iron. How does the chain logic decide, which material is the correct one, and which link? How does it know that the link before it was made of the correct material? That is where the “hash” algorythms come up. On the one hand blockchains must be coded so as to make verification of previous blocks easy, on the other hand, creating a new block, and therefore a new version of the truth, must be a difficult and rigorous process.
Well, as far as the verification part goes, here the tyranny-of-the-majority aspect of blockchains becomes apparent: only that which is supported by the majority will continue the chain. But what about people that decide they like the brass chain? They may decide to keep using it and move away from the original chain. That is what happened to the original Ethereum coin which now has two types of the “one Ethereum” self.
Imagine that a neighbourhood of yours decides they prefer from now on to trade with Monopoly money instead of real money, and that all transactions after a given time need to be done in that new currency. That is a simplified way of how that works. A fork in the way. Forks can be pushed by users or by the community as well. Most (soft) forks work as updates to a ongoing chain, with the intention of improving the current code and for example fixing a security issue. But sometimes scammers try to force their code into the chain, and here decentralization shows its power: if most users doubt a fork’s seriousness, they can stop it. One might think though… and if most of the block building subjects agree to a scam? This is where the 51% comes in.
The 51% attack and FUD
Although that is not really true in life, despite what movies show, owning 51% of the block creating, i.e. mining, power of a block chain is in theory enough to enable the controlling entity to control of the chain and thus define what is its final truth. Block chains are protected against these kind of attacks by their own structure: every link carries with it the “hash”, a mark of the block before it, therefore making it very costly for would-be 51%s to convert all the blocks necessary to create the new valid reality.
A 51% attack is but one risk that blockchains face, as the technology matures so will the methods to attack it. This leads to discussions in specialized or public forums in a very heated manner. It is such a new technology that a lot of fear, uncertainty and doubt (i.e. FUD) surrounds it. FUD is the term used to describe a given analysis of the block chain or cryptocurrency discussion as merely fear inducing, instead of constructive.
On upcoming posts we dive into other aspects of blockchain technology, mentioned en passant above. Namely structural ones: permissions, the centralization question and a short summary of the proofs.