Almost everything you read about the blockchain is wrong. No new technology since the Internet itself has excited so many pundits, but blockchain just doesn’t do what most people seem to think it does. We’re all used to hype, and we can forgive genuine enthusiasm for shiny new technologies, but many of the claims being made for blockchain are just beyond the pale. It's not going to stamp out corruption in Africa; it's not going to crowdsource policing of the financial system; it's not going to give firefighters unlimited communication channels. So just what is it about blockchain?
The blockchain only does one thing (and it doesn’t even do that very well). It provides a way to verify the order in which entries are made to a ledger, without any centralized authority. In so doing, blockchain solves what security experts thought was an unsolvable problem – preventing the double spend of electronic cash without a central monetary authority. It’s an extraordinary solution, and it comes at an extraordinary price. A large proportion of the entire world’s computing resource has been put to work contributing to the consensus algorithm that continuously watches the state of the ledger. And it has to be so, in order to ward off brute force criminal attack.
How did an extravagant and very technical solution to a very specific problem capture the imagination of so many? Perhaps it’s been so long since the early noughties’ tech wreck that we’ve lost our herd immunity to the viral idea that technology can beget trust. Perhaps, as Arthur C. Clarke said, any sufficiently advanced technology looks like magic. Perhaps because the crypto currency Bitcoin really does have characteristics that could disrupt banking (and all the world hates the banks) blockchain by extension is taken to be universally disruptive. Or perhaps blockchain has simply (but simplistically) legitimized the utopian dream of decentralized computing.
Blockchain is antiauthoritarian and ruthlessly “trust-free”. The blockchain algorithm is rooted in politics; it was expressly designed to work without needing to trust any entity or coalition. Anyone at all can join the blockchain community and be part of the revolution.
The point of the blockchain is to track every single Bitcoin movement, detecting and rejecting double spends. Yet the blockchain APIs also allow other auxiliary data to be written into Bitcoin transactions, and thus tracked. So the suggested applications for blockchain extend far beyond payments, to the management of almost any asset imaginable, from land titles and intellectual property, to precious stones and medical records.
From a design perspective, the most troubling aspect of most non-payments proposals for the blockchain is the failure to explain why it’s better than a regular database. Blockchain does offer enormous redundancy and tamper resistance, thanks to a copy of the ledger staying up-to-date on thousands of computers all around the world, but why is that so much better than a digitally signed database with a good backup?
Remember what blockchain was specifically designed to do: resolve the order of entries in the ledger, in a peer-to-peer mode, without an administrator. When it comes to all-round security, blockchain falls short. It’s neither necessary nor sufficient for any enterprise security application I’ve yet seen. For instance, there is no native encryption for confidentiality; neither is there any access control for reading transactions, or writing new ones. The security qualities of confidentiality, authentication and, above all, authorization, all need to be layered on top of the basic architecture. ‘So what’ you might think; aren’t all security systems layered? Well yes, but the important missing layers undo some of the core assumptions blockchain is founded on, and that’s bad for the security architecture. In particular, as mentioned, blockchain needs massive scale, but access control, “permissioned” chains, and the hybrid private chains and side chains (put forward to meld the freedom of blockchain to the structures of business) all compromise the system’s integrity and fraud resistance.
And then there’s the slippery notion of trust. By “trust”, cryptographers mean “out of band” or manual mechanisms, over and above the pure math and software, that deliver a security promise. Blockchain needs none of that - so long as you confine yourself to Bitcoin. Many carefree commentators like to say blockchain and Bitcoin are different things, yet the connection runs deeper than they know. Bitcoins are the only things that are actually “on” the blockchain. When people refer to putting land titles or diamonds “on the blockchain”, they’re using a short hand that belies blockchain’s limitations. To represent any physical thing in the ledger requires firstly a schema – a formal agreement about which symbols in the data structure correspond to what property in the real world – and secondly a process to bind the owner of that property to the special private key (known in the trade as a Bitcoin wallet) used to sign each ledger entry. Who does that binding? How exactly do diamond traders, land dealers, doctors and lawyers get their blockchain keys in the first place? How does the world know who’s who? These questions bring us back to the sorts of hierarchical authorities that blockchain was supposed to get rid of.
There is no utopia in blockchain. The truth is that when we fold real world management, permissions, authorities and trust, back on top of the blockchain, we undo the decentralization at the heart of the design. If we can’t get away from administrators then the idealistic peer-to-peer consensus algorithm of blockchain is academic, and simply too much to bear.
I’ve been studying blockchain for two years now. My latest in-depth report was recently published by Constellation Research.