Quantum Computers and Crypto

Quantum computers are powerful machines that can solve complex equations much more quickly than regular computers.

Computers that we know today can be called classical computers. This means that computations are done in a sequential order — a computational task is executed, and then another one can be started. This is due to the fact that the memory in a classical computer must obey the laws of physics and can only have a state of either 0 or 1 (off or on).

There is a class of computers currently in their very early stages of development for which these classes of problems would be trivial to solve — quantum computers. Quantum computers are based on fundamental principles described in the theory of quantum mechanics, which is concerned with how subatomic particles behave.

In classical computers, a bit is used to represent information, and a bit can have a state of either 0 or 1. Quantum computers work with quantum bits or qubits. A qubit is the basic unit of information in a quantum computer. Just 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 both 0 and 1 at the same time.

Unfortunately, a side effect of these quantum computers would be that the algorithms that form the basis of asymmetric cryptography would become trivial to solve, fundamentally breaking the systems that rely on them.

Asymmetric cryptography, also known as public-key cryptography, is a process that uses a pair of related keys — one public key and one private key — to encrypt and decrypt a message and protect it from unauthorized access or use. A public key is a cryptographic key that can be used by any person to encrypt a message so that it can only be deciphered by the intended recipient with their private key. A private key — also known as a secret key — is shared only with key’s initiator.

The emergence of quantum computing technology could undermine the cryptography that underlies most of our modern digital infrastructure, including cryptocurrencies.

This would put the security, operations, and communications of the entire world at risk, from governments and multinational corporations to the individual user. It is no surprise that a considerable amount of research is being directed at investigating and developing countermeasures to the technology. Cryptographic algorithms that are assumed to be secure against the threat of quantum computers are known as quantum-resistant algorithms.

Bitcoin mining also uses cryptography. The miners are competing to solve a cryptographic puzzle in exchange for the block reward. If a single miner would have access to a quantum computer, it may gain dominance over the network. This would reduce the decentralization of the network and potentially expose it to a 51% attack.

However, according to some experts, this isn’t an immediate threat. Application-Specific Integrated Circuits (ASICs) can reduce the effectiveness of such an attack — at least for the foreseeable future. Also, if multiple miners have access to a quantum computer, the risk of such an attack is significantly reduced.

The crypto community should be ready for the inevitability of quantum computing: It’s not as distant a future as it might seem.

Many people harbor the fear that Sycamore, Google’s 54-qubit quantum processor, could outsmart the system and steal everyone’s Bitcoin. If there were to be no changes to the current implementation of the Bitcoin network, this would most likely become a reality within five to 10 years. So, while there is currently no need for users to worry, developers are well advised to commence preparations.

Should Bitcoin holders be concerned about the quantum problem in 2020? No, but there is a caveat: Cryptocurrencies (meaning their developer communities) and enterprises should focus on the issue.

What if there are quantum computers already built that are much more capable than Google’s Sycamore and we are just not allowed to know about them?

We should seek and upgrade to a quantum-resistant crypto stack in blockchain implementations and all other systems that depend on asymmetric crypto (e.g., banks, governments, etc.) as soon as possible. Quantum supremacy is inevitable — it’s just a case of when.