The Blockchain’s two most important inherent qualities are transparency and immutability. Most might argue that trust is another, but this essentially arises from a combination of the two already mentioned.
Transparency – which is essentially a reference to the open-source nature of DLT – is necessary because actors on the network need to know the rules of the game before participating themselves.
This seemingly impregnable security, on the other hand, is underlined by one very big assumption – namely that no-one has the ability to outgun the rest of the network
Immutability means that once data is committed to a block, the chances of that data being modified or eradicated essentially dissipate towards zero at a rate of exponential knots as newer blocks are piled on top.
This trust in the data is further buttressed by the fact that that nothing can be committed to the blockchain unless it has been subjected to the consensus mechanism of the particular blockchain protocol in question.
This seemingly impregnable security, on the other hand, is underlined by one very big assumption – namely that no-one has the ability to outgun the rest of the network in terms of computing power.
If anyone wants to mount an attack against the Bitcoin network, for example, they would need to perform a so-called 51% percent attack that would then allow them to dominate the behaviour of the network, the decisions it makes and thus the transactions which are approved.
The hacker, in this theoretical instance, could even rewrite older transactions and thus reverse them – although the older the transaction, the harder this will be. In practice, this essentially means that blockchain technology is, as things stand, un-hackable.
The Power of Quantum
The problem, however, is that theory – with the advent of quantum computing specifically – appears to be catching up with practice, and some are now warning that the threat may be no further than ten years down the line.
Google’s own quantum computer, for example, is thought to have demonstrated an ability to perform certain simple tasks anything up to 100 million times faster than what can be achieved by a standard desktop computer today.
The reason why quantum computing is so powerful can be attributed to the concept of a qubit. A qubit is the quantum equivalent of a traditional computing bit. Unlike a classical computing bit which can only represent two states, however – traditionally labelled ‘0’ and ‘1’ – a qubit can represent a larger number of states depending on how the quantum machine itself is configured.
For a quantum computer that is built from three-state qubits, for example – the simplest quantum computer one can have – an 8-qubit processor can represent 6561 different permutations; that is over twenty-five times more powerful than its traditional 8-bit counterpart.
Add more bits again, and the advantage is compounded further – a 32-qubit machine can outperform a 32-bit machine by a factor of almost four hundred thousand. At 64 bits, the difference in performance becomes almost unfathomable.
And remember, we are still only talking about 3-state qubit machines here. If we get there, higher order qubit machines take us into an entirely new paradigm of its own.
Whilst theory now demonstrates a threat to blockchain security, however, theory also points to quantum-based solutions that are now setting out to counter this Sword of Damocles. And a number of people are on the case.
Those who are now developing the foundations of quantum-resistant security solutions are not merely doing so out of dear love for the blockchain concept, however. Blockchain technology is still in its infant stages – but the cryptographic methods which underpin its security are in widespread use elsewhere and this is where the real concern arguably lies.
RSA cryptography, which serves as the bedrock for today’s online traditional banking, will likely make a first point of call for the quantum hackers of the future. And it is for this reason that the world’s leading cryptographers are already on the case for devising new methods of deriving public-private key pairs that will be resistant to quantum attacks.
These new methods themselves appear likely to be quantum-derived although that doesn’t imply the need for quantum computers themselves.
Even if these newly emerging initiatives to stave off the threat of quantum technology don’t succeed, however, there may as yet be little reason to panic.
Firstly, quantum computers remain a long way off from achieving the kind of stability necessary to become commercially viable. IBM’s own 50-qubit machine is thought to be able to perform its calculations for no longer than a fraction of a second.
Secondly, a quantum machine requires housing in the kinds of temperatures that are generally only found in deep space. The implication is that, when quantum computers do become commercially viable, they will do so as a cloud-based service that offers the ability to perform a fixed set of limited tasks only – and therefore something which, by definition, hackers will be unlikely to exploit for their own specific ends.
Those who do manage to create an industrial-scale, viable quantum machine will, on the other hand, likely have better things to do with their resource than hack into someone’s bank account.
And whilst Bitcoin may make for a nice $100 billion dollar target, any undermining of the network through a successful hacking episode will likely reduce its value to zero – so any hacking attempt, with all the resources that this implies, would not be for self-gain.
Although, this said, any quantum hacker may still be tempted to take down the Bitcoin network for the simple reason that it sends out a powerful message – there’s a new toy in town that is even more impressive than the blockchain itself.