Quantum computers are a potential threat to crypto and blockchain networks. That's why the announcement of Google's quantum computer got a lot of people in blockchain and crypto talking. Maybe these computers can launch an attack on a blockchain network or crack the code to our private keys. However, these threats are not practical at the moment and the cryptography world is already building its fortress.
Researchers from Google and NASA have claimed quantum supremacy. They have build a quantum computer that's capable of performing a computational task that would take a supercomputer 10 thousand years. The quantum computer called Sycamore did it within 3 minutes. Even though there's some controversy surrounding these claims, it remains true that a team of researchers have build a very, very powerful computer. Now how does this relate to blockchain and cryptocurrencies?
Cryptocurrencies are build on blockchain technology. To have a blockchain network run smoothly, 51 percent of the network should be working with the same intention. However, when a hacker manages to claim 51 percent of the total computing power he can control the network and create fake transactions. This is called a 51% Attack, and has happened to several networks on several occasions over the years.
If a quantum computer is thousands of times stronger than a normal computer, then it seems likely that such a monster computer is able to take over a blockchain network easily. Therefore quantum computers are a potential threat to crypto and current blockchain networks, like Bitcoin, Ethereum, Litecoin and Dash.
The Bitcoin network is build with millions of nodes and miners around the world. A quantum computer could potentially launch an attack on the Bitcoin network. According the Bitcoin Core developer Peter Todd there's no need to worry, as Google's Sycamore is 'a primitive type of quantum computer'.
“It means nothing because Google’s quantum breakthrough is for a primitive type of quantum computing that is nowhere near breaking cryptography… We still don’t even know if it’s possible to scale quantum computers; quite possible that adding qbits will have an exponential cost.”
Peter Todd (Twitter, September 24th 2019)
Even if quantum computers are ever capable of effectively take part in the crypto mining process of a blockchain, it still remains to be seen whether that would truly be a problem. According to a report from the QAN Platform an attack on the Bitcoin network would still be useless, even if an attacker would use a quantum computer. This has something to do with the way the SHA256 encryption works, but let's put that idea aside for now. (QAN Report, p 33)
Google's quantum computer runs on 54-qubit chip. A normal computer works with bits, which can be either 0 or 1. Qubits however, can be a two numbers at the same time: 00, 01, 10 or 11. This allows for much more computing power. But the computer costs a lot of money: development, space, power etc.
The Trump administration has pumped 1.2 billion dollars in the development of a quantum computer. Over the past few years companies like Google, IBM, and Intel have received at least 450 million dollars in private funding, according to Nature.
To make things worse, despite all the investments there's no actual use-case scenario yet. That's something that will come over time. For now it's enough to know that a quantum computer can perform certain tasks much faster than a supercomputer.
According to Nature a general purpose quantum computer requires at least one million qubits. Developing this type of computing power would require a lot more time, work and money. Quantum computers needs to become 18.519 times faster before it's capable of any general purpose tasks.
Not everybody sees a threat in the rise of quantum computing. A researcher from the University of Texas believes that quantum computers might benefit the Proof-of-Stake crypto protocol. For example quantum computers like Sycamore could perfect the Proof-of-Stake crypto mining process, according to researcher Scott Aaronson in an interview with Forbes.
Where mining rewards in the Proof-of-Work mining system are based on computing power, Proof-of-Stake relies on picking a random user with 'staked' coins to determine who receives these coins. As a result Proof-of-Stake is not only more energy efficient, it's also potentially more decentralized. However, the current system is flawed as current computers aren't capable of true random number picking.
Aaronson believes that the computing power of a quantum computer can solve this issue. Google's Sycamore quantum computer operates with a 54-qubit processor. As a result it can generate numbers much faster, and it's capable if truly picking a random number.
For years cryptocurrency developers have been talking about the potential threat of quantum computers. Researchers have been publishing papers on quantum computing, and crypto developers have already created encryption methods that would be 'quantum resistant'. They call this Quantum Hardness.
Quantum hardness is related to post-quantum cryptography. This is a relatively new school of cryptography dedicated to creating cryptographic algorithms that are thought to be able to withstand an attack by quantum computers.
QAN Platform, Quantum Computing and Blockchain: The Definitive Guide (PDF)
Blockchain developers and cryptography researchers are already ahead of the game. By the time a powerful quantum computer would show up, blockchain projects and cryptocurrencies would already have implemented security systems. This can for example by done by using only one-time addresses. That way computers can never crack an encryption key.
Post-quantum cryptography is already under heavy development. Three years ago the National Institute of Standards and Technology (NIST) initiated a program aimed at developing and identifying quantum hard public-key cryptographic algorithms. Remarkably, the organization is a non-regulatory agency of the U.S. Department of Commerce.
NIST wants to develop cryptography that also works on the smallest devices. Smart cards, tiny devices for the internet-of-things, and every other online connected device needs to be able to protect itself against a quantum computer.
"We want quantum-resistant algorithms that can perform this sort of lightweight cryptography”,
Dustin Moody, NIST mathematician (press release January 2019)
Even though quantum computers are a potential threat, the cryptography world is already seeking answers to questions to still need to be asked. Many current blockchain projects might not be resistant to the power of quantum computers, but at the moment these quantum computers can't do anything that's remotely useful let alone cracking private keys or taking over a network.
Interestingly the United States National Security Agency are developing a quantum-resistant cryptocurrency. The NSA is doing this to battle cyber threats from other countries. North Korea, China, Russia and Iran are the main threat. A quantum-resistant cryptocurrency is supposedly needed to remove the threat of cyber warfare.
