Quantum computers will instantly break all encryption

What we know

Quantum computers use principles of quantum mechanics, such as superposition and entanglement, to perform certain types of calculations fundamentally differently from classical computers, and for specific mathematical problems, this different approach can offer dramatic theoretical speed advantages. The most relevant such problem for cybersecurity is integer factorization, breaking a large number down into its prime factors, which underlies the security of widely used public-key encryption systems including RSA. Peter Shor's 1994 algorithm demonstrated mathematically that a sufficiently powerful quantum computer could factor large numbers exponentially faster than the best known classical algorithms, which would indeed undermine RSA encryption's security if such a machine were built at sufficient scale.

However, building a quantum computer capable of running Shor's algorithm against real-world encryption key sizes (typically 2048 bits or larger for RSA) requires a number of stable, error-corrected quantum bits (qubits) far beyond what any quantum computer has achieved as of the mid 2020s. Current quantum computers, including IBM's and Google's most advanced systems, operate with a few hundred to roughly a thousand physical qubits, and these qubits are highly error-prone, requiring extensive error correction that consumes many physical qubits to produce a smaller number of reliable "logical" qubits; expert estimates published by organizations including the National Institute of Standards and Technology and academic quantum computing researchers generally suggest that breaking RSA-2048 encryption would require on the order of many thousands to millions of stable logical qubits, a scale not yet achieved and without a confidently predictable near-term timeline, according to assessments from major quantum computing research groups and industry roadmaps as of the mid 2020s.

Critically, not all encryption is equally vulnerable to quantum computing even in a future scenario where large-scale quantum computers become available. Symmetric encryption algorithms, such as AES, which is widely used to secure data at rest and in many communication protocols, are considered much more resistant to quantum attack; Grover's algorithm, the relevant quantum algorithm for attacking symmetric encryption, offers only a quadratic speedup rather than the exponential speedup Shor's algorithm provides against RSA, meaning AES's security can be preserved against quantum attack simply by using longer key lengths (such as AES-256 instead of AES-128), a comparatively straightforward mitigation already recommended and implemented in many security standards.

The cybersecurity and cryptography community has been actively preparing for the eventual arrival of practical quantum computers for years, not simply reacting after the fact. The National Institute of Standards and Technology ran a multi-year public competition and selected several "post-quantum cryptography" algorithms, published as finalized standards in 2024, specifically designed to resist quantum computer attacks using entirely different mathematical foundations than RSA's factorization-based approach, and many governments, financial institutions, and technology companies have already begun transitioning critical systems toward these quantum-resistant standards well ahead of quantum computers reaching the scale needed to threaten current encryption. The evidence-based summary is that quantum computing poses a real, well understood, and actively being addressed future threat to specific encryption types, not an imminent, already-arrived collapse of all cybersecurity, and the claim that quantum computers "break everything" overstates both current quantum hardware capability and the uniform vulnerability of all cryptographic methods.

Common claims

• Quantum computers can already break encryption.False. Cryptographically relevant quantum computers do not yet exist.
• When quantum computers arrive, all encrypted data will be instantly accessible.Overstated. Breaking specific keys would take hours or days, not seconds.
• There is nothing we can do to prepare for quantum threats.False. NIST finalized post-quantum cryptography standards in 2024.

Evidence hierarchy

All sources

• Post-Quantum Cryptography StandardizationNational Institute of Standards and Technology · 2024
• Polynomial-Time Algorithms for Prime Factorization and Discrete Logarithms on a Quantum ComputerPeter Shor, SIAM Journal on Computing · 1997
• Quantum Information Science researchNational Institute of Standards and Technology · 2023
• IBM Quantum computing roadmap and hardware progressIBM Research · 2024

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