In the cryptocurrency community, there is a lurking fear about quantum computing due to its potential ability to break cryptocurrencies and the encryption that secures them. Many actors in the crypto space are apprehensive about losing the security of their private keys as more headlines emerge touting imminent “quantum supremacy.”
New advancements in quantum technology and algorithms could subvert established digital security features using two key types of attack: the storage attack and the transit attack. The former involves a malicious actor with quantum capabilities targeting vulnerable addresses to steal funds. The latter involves a malicious actor with large-scale quantum capabilities attempting to hijack a blockchain transaction in transit and transfer the funds to their address instead.
However, the blockchain is not under any significant threat from quantum computing for the following reasons:
Current Cryptography Techniques
Whereas it is easy to multiply small numbers to generate giant ones, going in the opposite direction is significantly harder; it is impossible to look at a number and tell its factors. This principle is the basis of one of the most popular data encryption forms, the RSA.
RSA security can only be decrypted by factoring the product of two prime numbers, each of which is usually hundreds of digits long. These numbers serve as unique keys to a problem that is effectively unsolvable if you need to know the answers.
In 1995, however, mathematician Peter Shor of AT&T Bell Laboratories developed a new algorithm for factoring prime numbers, whatever the size. IBM built a device for quantum computing in 2001, with seven qubits made from atomic nuclei, to demonstrate Shor’s algorithm.
The experiment was a success, and the machine ran Shor’s algorithm to factor 15 into 5 and 3—hardly an impressive calculation but an outstanding achievement simply proving the algorithm works in practice. Theoretically, a powerful enough quantum computer could implement Shor’s algorithm to hack everything from bank records to personal files.
Cryptocurrencies like Bitcoin, Ethereum and others are developed using blockchain technology that allows parties to perform peer-to-peer transactions in a system that is not controlled by a centralized authority. Instead, blockchain provides a trust framework that is sustained by cryptographic algorithms. Cryptocurrencies are secured through public key cryptography, which combines a public key that anyone can see with a private key for each user’s eyes only.
Bitcoin uses the SHA-256 cryptographic protocol, which today’s computers cannot break. The crypto community fears that as quantum computers evolve, there is an increased potential for quantum-equipped actors to steal huge quantities of cryptocurrencies by abusing the computational advantage offered by quantum computers.
New advancements in quantum technology and algorithms could subvert established digital security features using two key types of attack: the storage attack and the transit attack. The former involves a malicious actor with quantum capabilities targeting vulnerable addresses to steal funds, while the latter involves a malicious actor with large-scale quantum capabilities attempting to hijack a blockchain transaction in transit and transfer the funds to their address instead.
Classic Computers versus Quantum Computers
Quantum computing is undoubtedly vastly different from classical computing. Indeed, according to physicist Shohini Gose of Wilfrid Laurier University, the difference between classical computing and quantum computing is akin to the difference between light bulbs and candles; the light bulb is not merely a better candle but something entirely different altogether.
Quantum computing is a process that uses the laws of quantum mechanics to solve problems that are too large or complex for classical computers, using multidimensional quantum algorithms.
While classical computers utilize binary bits, the basic unit of information in quantum computing is known as qubits. Binary bits are often silicon-based chips and can only represent two states, 0 or 1. On the other hand, qubits come in different forms depending on the architecture of the particular quantum systems since some require extremely cold temperatures to work properly. They can be made from photons, trapped ions, and artificial or real atoms. Furthermore, qubits use superposition to be in multiple states simultaneously. A qubit can be 0 or 1 and any part of 0 and 1 in a superposition of both states.
Unlike classic supercomputers, quantum computers are more elegant, smaller, and require less energy. An IBM quantum processor is a wafer much the same size as the one found in a laptop, whereas its hardware system is approximately the size of a car and consists mostly of cooling systems to maintain the superconducting processor at its ultra-cold operational temperature. To comprehend how quantum computing works, it is necessary to understand entanglement, superposition, and quantum interference.
Superposition, Entanglement, and Interference
Superposition
To explain superposition, some use the analogy of Schrodinger’s cat, while others refer to the moments in which a coin is in the air during a coin toss. Simply put, quantum superposition refers to the scenario where quantum particles combine all possible states; they continue to fluctuate and move while the quantum computer measures and observes each one.
Significantly, rather than the two-things-at-once point of focus, superposition is the ability to view quantum states in multiple ways and ask them different questions; essentially, unlike a traditional computer that has to perform tasks sequentially, a quantum computer can run an enormous number of parallel operations.
Entanglement
Quantum entanglement refers to the state where quantum particles can correspond to measurements. In this state of entanglement, measurements taken from one qubit can be used to make conclusions about other units; when particles are entangled, none of them can be described without reference to the others. Entanglement enables quantum computers to calculate bigger stores of data and information, thereby solving larger problems.
Quantum Interference
As qubits undergo superposition, they are also susceptible to quantum interference which is the probability of qubits collapsing one way or another. Qubits require a great degree of maintenance as any number of simple actions or variables risk sending error-prone qubits into decoherence.
Merely using a quantum computer to measure qubits or execute operations is enough to crash it. Additionally, even small vibrations or temperature changes will cause decoherence of qubits. For this reason, quantum computers are kept isolated, with the ones that use superconducting circuits being kept at near absolute zero- or -460 degrees Fahrenheit.
According to Jonathan Carter, a scientist at Lawrence Berkeley National Library, the two challenges that need to be overcome are imbuing individual qubits with better fidelity and arranging them to form logical qubits.
Carter estimates that to form one fault-tolerant qubit, “hundreds to thousands to tens of thousands of physical qubits” will be required, and he posits that none of the technology available at the moment could scale to those levels.
Why Blockchain Is Not at Risk from Quantum Computing
The good news for crypto enthusiasts is that the quantum computing problem can be fixed by implementing post-quantum cryptography technology, which is emerging simultaneously as blockchain. The United States National Institute of Standards and Technology (NIST) is, in the same vein, trying to get ahead of the challenge and is currently seeking out quantum-proof cryptography algorithms with the involvement of researchers worldwide.
Quantum computers are also notoriously prone to crashing due to noise and decoherence. They are very delicate and can crash because they are put into use or due to tiny vibrations. Quantum computers must operate under special conditions, such as extremely low temperatures or being kept in a vacuum chamber. They also make it difficult to build a stable enough quantum computer to break the blockchain’s encryption.
Additionally, we still need more computational power to threaten cryptocurrencies; the computing power to carry out a storage attack, for instance, is estimated at around 10 million qubits, significantly higher than the hundred or so bits currently available.
Even with billions of dollars worth of investment from governments and the world’s biggest corporations signalling that the race for quantum capabilities is well underway, serious quantum computers are still a way off.