On January 25, 2026, a16z Crypto released a technical analysis report titled "Quantum Computing and Blockchain: Matching Urgency with Actual Threats," systematically assessing the real impact of quantum computing on the security of public blockchains. The key judgment given in the report is that the probability of a quantum computer capable of breaking mainstream crypto assets (CRQC) appearing before 2030 is extremely low; the current more realistic risks are concentrated on the design and implementation flaws of protocols like Bitcoin and Ethereum. It is important to emphasize that this "extremely low risk before 2030" time assessment comes from a single report, not an industry consensus. However, it clearly exposes a neglected mainline conflict: on one side, there are those who treat "quantum doomsday" as a disaster that could strike at any moment, while on the other side, there are those who regard quantum computing as mere hype and completely ignore it. The real urgency lies in how the protocol and governance layers can achieve self-rescue under the shadow of quantum threats, rather than waiting for a dramatic moment of quantum attack.
The Rise of Quantum Doomsday Narratives: Panic
● In recent years, media and markets have frequently exaggerated a dramatic scenario: the moment a sufficiently powerful quantum computer is activated, the private keys of Bitcoin and other public chains are instantly deduced one by one, and on-chain assets are looted within seconds. This narrative often describes quantum computing as a "super-powered brute-force cracking machine," flattening the complexities of cryptography layers, protocol design, and actual attack costs, leaving only a simple terrifying label—"once quantum arrives, the crypto world is wiped out."
● In contrast to this sensational picture, the time scale provided by the a16z report is calm: the emergence of a CRQC capable of substantially breaking mainstream blockchain encryption before 2030 is assessed as an "extremely low probability" event; quantum computing is more like a long-term security constraint rather than an imminent disaster. This judgment represents only a single research perspective, but it at least reminds the industry that viewing the quantum threat as an immediate black swan does not match the reality of technological progress, and excessive emotionality will only dilute the risks that truly need to be prioritized.
● The vast majority of discussions surrounding "quantum doomsday" overlook the technical layering between cryptography and blockchain: the vulnerabilities of cryptographic algorithms, signature mechanisms, scripting systems, and network layers differ, and the actual attack paths are complex and costly. Compressing all this complexity into a single statement like "once quantum comes, everything is gone" facilitates dissemination but greatly misleads the direction of security investment, creating a saturated emotional state and an information-poor "quantum doomsday" label.
The Real Danger Does Not Lie in the Cryptographic Layer
● The report emphasizes the HNDL attack, highlighting that the impact of quantum computing on different cryptographic components is not uniform: the threat to certain cryptographic schemes may be controllable, but the attack window for signature exposure and observable public keys is more direct. In other words, whether the cryptographic layer is instantly breached is highly related to how the public key of the signature layer is exposed and reused. Different modules have different pressure points, and the claim that "quantum will destroy everything" does not hold up technically.
● Comparing Bitcoin and Ethereum, it can be seen that the more urgent security risks do not lie in the future where quantum hardware has yet to arrive, but in protocol design flaws, implementation vulnerabilities, and slow governance mechanisms. Bitcoin's long-standing adherence to minimal scripting and slow-paced upgrades means that once a system-level flaw or quantum-related risk arises, the governance layer lacks the space for rapid adjustments; while Ethereum, although more flexible in governance, has a complex execution environment and frequent upgrades that similarly amplify the risks of implementation bugs and economic attacks. These are security shortcomings that already exist in the real world and have been continuously exposed.
● Based on this, the a16z report gives a clear stance: developers should prioritize allocating resources to auditing and formal verification to compress the attack surface of existing protocol and implementation layers, rather than hastily pushing for a network-wide "quantum migration" when both technology and governance are not yet prepared. The latter is not only difficult to implement but may also be undermined by the new complexities and governance splits introduced before any quantum attacks are even seen.
Bitcoin's Old Coin Minefield: Quantum Shadows
● The so-called "quantum-vulnerable legacy coins" refer to those that use early or weak signature schemes, have addresses that have already exposed public keys, or may even have lost private keys. There are a large number of early addresses and long-dormant balances on the Bitcoin chain, some of which are more sensitive to future quantum attacks by design. Once practical quantum capabilities emerge, theoretically, these old coins will be the first to be exposed to risks that can be prioritized for scanning and theft.
● A striking point in the a16z report states: "The issue of quantum-vulnerable legacy coins faced by Bitcoin is essentially a governance challenge on-chain." How to deal with this batch of old coins affects both system fairness and market expectations regarding supply limits and prices. If old coins are "forcibly reinforced" or rules rewritten through soft or hard forks, it will inevitably ignite ideological debates about the sanctity of ownership and the immutability of code; if completely ignored, it would mean acknowledging the existence of a high-value "minefield" within the system.
● In contrast, public chains like Ethereum, which have relatively flexible governance, theoretically find it easier to coordinate some gradual migration plans within consensus, such as guiding users to voluntarily migrate to safer script or account structures through contract tools and incentive mechanisms. However, Bitcoin's inherent conservative philosophy and slow upgrade pace create a sharp internal conflict between "upgrading security" and "maintaining fundamentalist beliefs," with quantum-vulnerable legacy coins being a concentrated projection of this governance paradox.
From Panic to Prioritization: Development
● a16z clearly suggests that prioritizing auditing and formal verification should become the main focus of current security investments. This type of work directly addresses the real risks at the protocol and implementation layers: through formal specifications, model checking, and rigorous audits, potential defects that could lead to inflation vulnerabilities, permission bypasses, or economic game imbalances can be identified in advance, significantly reducing the probability of the system being attacked under existing computational assumptions. This type of defense is "immediately effective," while quantum migration is more of a long-term project without a timetable.
● If large-scale modifications are made to the underlying protocol for "preventing quantum" while the quantum threat is still in the distant and highly uncertain stage, new script rules, key schemes, and governance processes will introduce entirely new attack surfaces and complexities. Historical experience shows that major version upgrades often come with unexpected compatibility issues and implementation errors, and may also create route disputes within the community, triggering long-term splits and soaring coordination costs, weakening the system before any quantum attacks are actually seen.
● The report also mentions that new cryptographic components like zkSNARK are, on one hand, key infrastructure for scalability and privacy, directly benefiting from cutting-edge cryptography; on the other hand, the long-term robustness of these proof systems based on complex assumptions in the quantum era needs to be evaluated independently of traditional signature and encryption schemes. In other words, while the industry enjoys the throughput and privacy dividends brought by zk technology, it must simultaneously plan their quantum-resistant pathways, rather than simply assuming that "cutting-edge equals secure."
Layered Risk Perspective: Cryptographic Layer and Signature Layer
● From a technical layering perspective, blockchain security can be roughly broken down into: the cryptographic layer responsible for confidentiality and partial structural security, the signature layer responsible for identity authentication and transaction authorization, and the zkSNARK components providing verifiable computation and privacy expansion. In the quantum era, the vulnerabilities and migration difficulties faced by these three are entirely different: some may only require algorithm replacement, while others may involve entire address formats, script semantics, or even consensus logic, with migration costs differing exponentially.
● HNDL-type attacks are particularly sensitive to signature exposure: once public keys are exposed on-chain for extended periods, addresses are reused repeatedly, or multi-signature scripts are overly transparent, quantum attackers can prioritize locking onto these high-value targets without needing to conduct indiscriminate scans across the entire network. Address reuse makes it easier for attackers to focus on the "highest yield public key set," and if multi-signatures and complex scripts are not well hidden or layered, they may become information overload "attack indicators" in a quantum environment, amplifying the risk exposure at the system level.
● For the zk field, a long-term dilemma may arise: on one hand, the significant system dividends brought by privacy protection and scalability lead to an increasing reliance on zk proofs for more assets and transactions; on the other hand, there is a continuous demand for new quantum-resistant proof systems, which are typically more complex, harder to audit, and have higher performance costs. Finding a balance between performance, privacy, auditability, and quantum durability will determine the shape of the next generation of zk infrastructure and whether they are a secure fortress or a new single point of risk under the "quantum narrative."
Quantum Threats Are Not a Farce: How to Address Them
The core message of a16z's report can be summarized in one sentence: the quantum threat truly exists in the long term, but the probability of CRQC directly breaching mainstream public chains before 2030 is extremely low and should not be rendered as a catastrophic disaster that will erupt tomorrow. In comparison, the more urgent security shortcomings currently focus on the protocol and governance layers, especially Bitcoin's governance dilemma regarding quantum-vulnerable legacy coins—how to find a widely accepted handling path for that portion of potentially high-risk legacy assets without tearing apart consensus.
For the entire industry, a more pragmatic course of action is to advance in phases: in the short term, focus resources on code security, auditing, and formal verification to patch visible vulnerabilities in existing protocols and implementations, while enhancing transparency and responsiveness in governance processes; in the medium to long term, plan a quantum-resistant evolution path within the consensus framework in an open and gradual manner, including strategies for replacing signature schemes, account models, and zk components. The quantum storm will come sooner or later, but what truly determines whether the industry can weather the storm is not the volume of disaster narratives, but the prioritization of self-rescue that begins today.
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