Post-quantum cryptography does not signal an imminent end.

Common Misconceptions About Quantum Threats Being Overestimated

(Source: a16zcrypto)

Recently, claims that quantum computers will soon break all cryptography have become widespread, fueling demands for the immediate and universal adoption of post-quantum cryptography. These arguments often overlook two critical issues:

• Quantum computers capable of practical cryptographic attacks have not yet been developed

• Quantum risks vary fundamentally across different cryptographic technologies

Ignoring these differences can lead to poor decisions regarding cost, efficiency, and security.

What Is a Quantum Computer of Cryptographic Significance?

A quantum computer of cryptographic significance is not simply an experimental device demonstrating quantum advantage. It refers to a fault-tolerant quantum system capable of running Shor’s algorithm and breaking RSA-2048 or secp256k1 in a reasonable timeframe.

Current public technological advances—whether in superconducting quantum, ion trap, or neutral atom architectures—have yet to achieve the required number of logical qubits and error correction depth. Even systems with thousands of physical qubits remain insufficient for genuine cryptographic attacks. Media and businesses often employ vague terms like quantum advantage and logical qubits to generate urgency, but there is still a gap of several orders of magnitude between these milestones and actual cryptographic threats.

zkSNARKs and Quantum Risk in Blockchain

Zero-knowledge proofs (zkSNARKs) share a similar quantum security profile with digital signatures:

• The zero-knowledge property itself is secure against quantum attacks

• There is no risk of data being collected now and cracked in the future

As long as the proof is generated before quantum computers emerge, its validity cannot be retroactively compromised. The actual risk only applies to proofs generated after quantum computers become available.

Most Blockchains Are Not Vulnerable to HNDL Attacks

Non-privacy public blockchains such as Bitcoin and Ethereum mainly use cryptography for transaction authorization, not data encryption:

• On-chain data is inherently public

• The quantum threat concerns potential future signature forgery, not the decryption of historical transactions

Applying HNDL risk directly to Bitcoin is a common yet serious misinterpretation.

Privacy Chains Are the Real Cause for Concern

Privacy-oriented blockchains conceal transaction amounts and recipients. If their encrypted content is decrypted after the fact, historical transactions could be traced and exposed. These chains do need to consider post-quantum or hybrid solutions earlier.

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Summary

Post-quantum cryptography is an unavoidable future direction. For encrypted communications requiring long-term confidentiality, action is urgent. For blockchain signatures and zero-knowledge systems, however, excessive haste may incur higher costs. Only by precisely aligning threat levels and technological readiness can we avoid being undermined by implementation risks before quantum threats actually arrive.