TechFlow News: On January 25, a16z Crypto posted on X stating that the timeline for cryptographically relevant quantum computers (CRQCs)—quantum computers capable of breaking cryptocurrency cryptography—is widely exaggerated. The likelihood of such machines emerging before 2030 is extremely low, and quantum risks vary significantly across different cryptographic primitives.
a16z argues that post-quantum cryptography must be deployed early to mitigate “harvest now, decrypt later” (HNDL) attacks. In contrast, post-quantum signatures and zkSNARKs are not vulnerable to HNDL; premature migration to these alternatives may instead introduce new risks—including performance degradation, immature implementations, and code vulnerabilities—and thus warrants a cautious, phased approach.
At the blockchain layer, most non-private public blockchains (e.g., Bitcoin, Ethereum) rely primarily on digital signatures for transaction authorization and therefore face no HNDL risk. Their quantum migration pressure stems largely from non-technical factors such as governance efficiency, social coordination, and technical execution. Bitcoin additionally faces challenges including slow governance and a large quantity of potentially abandoned tokens that remain vulnerable to quantum attacks. Privacy-focused blockchains, by contrast, conceal transaction details and thus genuinely face HNDL risk to confidentiality, warranting earlier transition.
a16z emphasizes that, in the foreseeable future, practical security threats—including software vulnerabilities, side-channel attacks, and fault-injection attacks—are far more urgent than quantum computing threats. Developers should therefore prioritize code auditing, fuzz testing, and formal verification.
