Bitcoin Magazine has published an article in its latest print package, The Quantum Issue, laying out what quantum computing is, how it differs from a regular computer, and why the subject matters to Bitcoin.
The piece, titled The Quantum Issue: WTF Is Quantum Computing?, says new Bitcoin users keep running into the same questions: what quantum computing is, how a quantum computer differs from a conventional machine, and what that means for Bitcoin. Author Shinobi frames the issue in stark terms. If a viable quantum computer is developed, he writes, it would raise an existential threat to Bitcoin because ownership of bitcoin rests on a basic assumption: unless a copy of a private key has been directly leaked, only the person holding that key can create a valid signature to move the coins secured by it.
How classical computers handle keys
The article describes classical computers as machines that store and manipulate information as strings of 1s and 0s. Every bit is exactly a 1 or a 0, with no ambiguity in between. When data is stored, it is stored as those binary values. When data is changed, the computer modifies it bit by bit, step by step. In that model, computation is linear. A machine has to execute the required steps one after another.
Using private key generation as an example, the article says a computer first obtains a random value, whether from dice input, user input or randomness produced by device hardware, and stores it in memory as 1s and 0s. It then multiplies that value by the elliptic curve’s generator point to derive a public key. At its most basic level, that process is an algorithm made up of instructions telling the machine which bits to take, how to modify them, which physical circuits to push them through, and how to write the modified value back into memory. There are more steps involved in producing a usable address, but the article says those details are not necessary for the point being made because they work the same way: step-by-step instructions acting on binary data in memory.
Why brute-forcing a Bitcoin private key is infeasible for a classical machine
The article then turns to the question of guessing someone else’s private key. It states that there are 2256 possible private keys, or 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,936 different possibilities.
A classical computer, the article says, would need to test those candidate private keys one after another, or as many as it can handle in parallel, while still following the same key-generation logic step by step. Trying more keys in parallel requires more computing power. Using less computing power means taking more time. Wanting less time means needing more computing power. The article argues there is no shortcut around that tradeoff.
Shinobi’s conclusion is that this task is impossible for a classical computer. On one side is a computation cost that all the computers on Earth could not pay. On the other is a time cost so large that every star in the universe would die before all possibilities had been checked. That is the point where the article introduces quantum computing as a different kind of option.
What makes a quantum computer different
Quantum computers are not, in the author’s framing, just faster computers. They work in a fundamentally different way. The basic unit of information in a quantum computer is a qubit, the quantum version of a bit. Unlike a classical bit, a qubit is not fixed as either a 1 or a 0 before observation. It exists in superposition, meaning it is simultaneously both a 1 and a 0 until it is observed, at which point it settles into one discrete state.
The article identifies entanglement as the other key building block. Qubits are not simply stored in isolation. The physical atoms representing them are entangled, and when those entangled atoms are observed and collapse into a single state, they collapse into the same state regardless of how far apart they are.
Shinobi notes that some hand-waving is unavoidable in a short explainer, but says the aim is to leave readers with an intuitive sense of the difference. In a classical computer, an algorithm is a sequence of instructions that takes one discrete state and transforms it, step by step, into another discrete state. Qubits, by contrast, do not store discrete states before observation. They store probabilities.
When a set of qubits of a given size is entangled, each possible state that the system could collapse into has a probability attached to it. Quantum algorithms, the article says, are not instructions for acting on definite states one by one. They are instructions for manipulating entangled qubits so that the probabilities of different outcomes change. Constructive interference is used to increase the probability of a correct answer, while destructive interference lowers the probability of incorrect answers. The article adds that this is not the same thing as the noise or interference that makes physical quantum computers hard to operate accurately.
Why that matters for Bitcoin
The article uses private key search to show the practical consequence. A classical computer trying to find the private key that matches a given public key would have to test candidate keys one by one. A quantum computer, using the right algorithm, could run a small number of times and arrive at the correct answer.
The author is careful on one point: this does not mean a quantum computer “checks every possibility at once.” Instead, it changes the probabilities of what a superposition will collapse into. That is why, in the article’s view, a quantum computer could break the assumptions behind elliptic curve cryptography while a classical computer could not. It is also why quantum machines are only useful for certain categories of computation, especially those with a massive space of candidate answers.
Serious risk, but not a call to panic
The final section is titled Don’t Panic. Shinobi writes that the difference between classical and quantum computation does mean one thing clearly: if a viable quantum computer is actually built and functions correctly, the basic assumption securing individual bitcoin holdings would be broken. In that case, those funds would no longer be secure.
At the same time, the article says the industry is not completely unprepared. According to the piece, the problem is understood, the exposure is understood, and a good number of possible solutions to different parts of the issue are beginning to come together. The article says, 「Breathe, and relax. Through the rest of this issue we are going to walk you through the whole problem.」
Bitcoin Magazine says the article appears in the latest print edition of The Quantum Issue and has been shared online as an early look at the ideas covered across the full issue. The post first appeared on Bitcoin Magazine and is credited to Shinobi.