Recently we all followed with attention a news that turned the world around in less than a second: "Google has developed a quantum computer", a powerful instrument capable of solving operations impossible to solve with conventional machines. I immediately thought: Could this new quantum computing be able to affect the security of Bitcoin, blockchain technology and the rest of cryptocurrencies?
Well, before answering my own concern it was necessary for me to seriously investigate what this quantum computing is all about that could be a threat to the world of cryptocurrencies. When we talk about quantum computing we refer to a field of computer science where the mathematical and logical theory of its operation is transferred to the atomic world. That is, it is an application of quantum mechanics in computing theories, to allow us to use the power of the atom and its states, to create extremely efficient computing equipment and algorithms based on the principles of uncertainty, probability and quantum states of systems.
It sounds rather confusing, almost like a science fiction movie, but these machines could penetrate, in just a few minutes, encryptions that would take today's fastest computers thousands of years. Consequently, most of today's digital security infrastructure could be at risk, including the Bitcoin blockchain and all other cryptocurrencies.
In classical computers, a bit is used to represent information, and a bit can have a state of 0 or 1. Quantum computers work with quantum bits or qubits. A qubit is the basic unit of information in a quantum computer. Like a bit, a qubit can have a state of 0 or 1. However, thanks to the peculiarity of quantum mechanical phenomena, the state of a qubit can also be 0 and 1 at the same time.
It is this quality of quantum computers that allows them to multitask at high speed. See, if I wanted to generate password combinations to penetrate your account security, it would take the fastest conventional computer at least a million years to figure it out, while it would only take a quantum computer a couple of minutes (maybe less).
Of course, beyond the possibility of using this technology for evil, quantum computing raises many situations that would help humanity in various fields such as medicine, architecture, science, agriculture and many more, where obviously computer security is also covered by this quantum life. In theory quantum encryption systems would be virtually invulnerable to attempts to decrypt any information. However, that is the theory and our current knowledge of quantum mechanics is incomplete. Because of this we can still keep in mind the mantra of any cybersecurity specialist: "No computer system is 100% secure, including quantum ones."
Recently a group of scientists from Shanghai University, demonstrated that the initial quantum cryptography models we know can be hacked. An achievement that they showed worldwide and of which they have published an interesting study. Yes, it is true, this is just beginning and surely Google, IBM or Microsoft are working hard on improving this technology before transferring it to our homes.
Now, what danger does quantum computing mean for cryptocurrencies? As we mentioned, quantum computing has the potential to break asymmetric cryptography. This means that every single blockchain and cryptocurrency we know of is at risk. Of course, this does not mean that cryptocurrency projects are unaware of this and have taken action to correct it. A good example of this is the myth that Bitcoin will come to an end when quantum supremacy (the ability to create high-capacity quantum computers) is achieved.
This myth is supported by the fact that ECDSA and SHA-256 could be broken by that method. As with all myths, there is some truth and a lot of misinformation. For example, to break ECDSA we need a quantum computer with a capacity of about 1500 qubits, something we are still far away from. In fact, the most powerful system we have now is only 54 qubits, in the hands of Google. This disproves that we are in imminent danger.
Secondly, in Bitcoin the creation of P2PKH (Pay To Public Key Hash) type transactions adds an additional security measure to protect the public keys from a possible attack of this type. By applying a SHA-256 and RIPEMD-160 hash on the public keys, we manage to obfuscate the key to prevent them from being attacked directly. This is certainly not a top-level security measure, but it effectively makes it difficult for a quantum computer to crack the public key and obtain the private key and thus gain control over our cryptocurrencies.
Security measures of cryptocurrency projects against quantum computing. Of course the above is only part of the security measures being taken to protect the security of cryptocurrencies. Other elements are under development and some are already in use for various projects today. For example, Zero Knowledge Proofs (ZKP) have enormous potential for resistance to quantum computing.
Other schemes known for their high resistance are XMSS (eXtended Merkle Signature Scheme), which is fully documented in RFC 8391. We can also mention SPHINCS, another cryptographic scheme resistant to quantum computing. Both schemes were designed by researcher Andreas Hülsing. We can also mention projects that seek to use Shor's algorithmic schemes, developed by Peter Shor in 1994, to achieve high quantum resistance.
In short, we are already in the construction of the pieces that can protect the blockchain and cryptocurrencies against this threat. For example, in Zcash and Monero they already use advanced cryptographic techniques that are resistant to quantum computing. Bitcoin as we have mentioned has also done this work, and is still working to implement Schnorr signatures and Confidential Transactions to its network natively. Projects like Ethereum are considering changing their signature schemes as well to address this problem.
But what is certain, is that quantum computing at the moment does not represent any real problem for the cryptography that protects cryptocurrencies. And with that, we can rest assured that these projects will be able to continue protecting our money as they have been doing. Best of all, it is knowing that in the face of the threat there are already appropriate responses to avoid the danger. Something unique that maintains confidence in cryptocurrency projects and the blockchain technology that supports them.