In This Article
Bitcoin's traditional cryptographic foundations, secure for decades, now confront a rapidly developing threat: quantum computing. Recent warnings by a Google quantum engineer and BlackRock's risk team suggest that "Q-Day," the day on which quantum computers crack Bitcoin's encryption, will arrive years earlier than the much-cited 2030 estimate. The announcement has propelled a sense of urgency among developers to render the network quantum-resistant before it's too late.
The Shortening Quantum Timeline
Bitcoin employs elliptic curve digital signature (ECDSA) algorithms to secure wallets. Although the algorithms are virtually unbreakable for regular computers, quantum computers using Shor's algorithm could potentially break them in a few minutes. Up until recently, this danger was thought to be decades away.
But in a May 2025 report, Google quantum scientist Dr. Elena Orlova warned that advances in error-corrected qubits would bring Shor-capable quantum computers within reach by 2027–2030, instead of 2040 as earlier estimated. BlackRock's risk unit echoed this in a client letter, stating that "quantum supremacy milestones are ahead of consensus forecasts," urging investors to make "Q-Day" part of long-term crypto strategy.
Why Bitcoin's Wallets Are Vulnerable
Most Bitcoin wallets are "reused addresses" (e.g., disposable ECDSA public keys). As soon as a quantum computer acquires the private key from a public key, it can drain the wallet. While newer wallets use "taproot" or "bech32" addresses that encrypt public keys until transactions occur, over 60% of Bitcoin's $1.3 trillion market capitalization remains in vulnerable legacy wallets, according to BitMEX Research.
The window to respond to this threat is closing faster than we ever realized," said Orlova. "Even a single working quantum machine in the wrong hands could target high-value wallets."
Post-Quantum Cryptography
Developers are exploring a number of promising approaches to defend Bitcoin against quantum attacks. Lamport signatures constitute one-time signature schemes that are Shor's-algorithm-resistant but at the expense of significantly larger transaction sizes, sometimes up to 100 times larger than current transactions. Yet another scheme, the XMSS (Extended Merkle Signature Scheme), is a hash-based one used already by quantum-resistant blockchains like QRL but requires wallet operators to work with complex "signature chains."
STARKs is a third scheme, which employs zero-knowledge proofs to hide public keys entirely, such as in Layer-2 networks like StarkWare, but this scheme introduces additional mathematical overhead and can slow down transaction verification. Each of these options is accompanied by its own trade-off in terms of blockchain size, complexity of operation, and verification speed.
Layer-2 Networks Lead the Way
While Bitcoin's base layer wrings its hands over upgrades, Layer-2 initiatives are already playing with quantum-resistant architectures. For example, engineers on the Lightning Network are prototyping "point-time-locked" quantum-safe contracts. Rootstock (RSK) is also in the process of integrating zk-STARKs to secure smart contracts, while multi-party computation (MPC) is employed by Fedimint community custody protocol to split private keys into quantum-proof shards.
According to Lightning Labs CEO Elizabeth Stark, "The goal is to build a bridge from today's Bitcoin to a post-quantum future. Layer-2 solutions allow us to innovate without waiting for consensus around a hardfork."
The Path Forward
Bitcoin's decentralized governance resists hurried upgrades. A quantum-resistant hardfork would require near-universal node acceptance — a process potentially taking years. Meanwhile, exchanges and institutional custodians like Coinbase and Fidelity are considering hybrid models, the combination of ECDSA with quantum-resistant signatures on large wallets.
"This is not a Bitcoin issue," said Orlova. "Every blockchain that uses ECDSA or RSA encryption is at risk. The entire digital economy needs to prioritize post-quantum standards today."
