Nick Carter says quantum computing is the biggest long-term risk to Bitcoin’s core cryptography and urges developers to treat it as an urgent matter, not science fiction.
In an essay published on Monday, the Coin Metrics co-founder explained in plain language how Bitcoin’s keys work and why quantum matters. Carter writes that users start with a secret number (a private key) and obtain a public key with elliptic-curve mathematics on the secp256k1 curve, which is the basis of ECDSA and Schnorr signatures.
He describes that transformation in a deliberate way: easy to calculate forward, impossible to reverse under classical assumptions. “The entire cryptographic basis of Bitcoin is that ‘there exists a one-way function that is easy to compute in one direction, and impossible to compute in the reverse,'” he writes.
To develop intuition, Carter compared the system to a giant number scrambler. He says the move from private to public works for honest users because they can use a shortcut called “double and add” to reach a conclusion quickly. He says there is no comparable shortcut in the opposite direction.
For non-experts, he offers a deck-shuffle analogy: you can repeat the same sequence of shuffles to reach the same final order, but an observer cannot look at the shuffled deck and guess how many shuffles were used.
Carter argues that the concern is that a sufficiently powerful quantum computer could destroy that asymmetry by making progress on the discrete logarithm problem that underlies Bitcoin’s signature. According to him, regular network behavior also increases the risk: When coins are spent, a public key is revealed on-chain.
He says it is safe today because converting a revealed public key back to a private key is not practical, but quantum advances could change that calculus, especially if addresses are reused and more keys remain visible for longer periods of time.
He is not calling for panic. Carter says the point is to plan.
In the near future, he highlights basic hygiene such as avoiding address reuse so that public keys are not exposed for longer than necessary. In the long term, he urges the community to prioritize post-quantum signature schemes and realistic migration paths, framing them as engineering work rather than far-out thought experiments.
The essay is the first in a short series; Carter said on X that Parts II and III will arrive in the next few weeks and will cover “post-quantum break scenarios”.