Main Points :
- Quantum computing poses a potentially existential threat to Bitcoin’s foundational cryptography.
- The transition to quantum-safe cryptography (post-quantum algorithms) is technically complex and requires community consensus.
- Investors—especially in Japan—must rethink the notion of Bitcoin as a “permanent safe asset” and incorporate technological risk hedging into their portfolios.
- Immediate steps for self-defence include avoiding public key reuse and migrating holdings from vulnerable addresses.
1. The Quantum Computing Threat: A “Biggest Risk” to Bitcoin’s Survival
1.1 How Quantum Computers Could Undermine Bitcoin’s Core
According to leading analysts, the rise of quantum computing has stirred up what might be described as Bitcoin’s greatest long-term risk: the possibility that quantum machines will break the cryptographic algorithms that underpin the network. For Bitcoin, much of its security model relies on the Elliptic Curve Digital Signature Algorithm (ECDSA) and SHA-256 hash functions.
If a sufficiently advanced quantum computer becomes available, it could exploit Shor’s algorithm to derive private keys from known public keys, allowing malicious actors to sign transactions and steal assets from wallets that have revealed their public keys. For example, once a Bitcoin address has broadcast its public key, the private key is theoretically vulnerable under quantum attack.
Moreover, a recent study by Deloitte estimated that about 25 % of all circulating Bitcoin might be at risk under certain quantum-attack assumptions.
1.2 A Technical Warning for a Market Fueled by Optimism
The fact that Bitcoin is widely regarded as “immutable” and “secure by design” has fostered a strong narrative of it being a near-immutable store of value. Yet that narrative may be challenged by technological evolution. Some investors may focus solely on price moves and short-term cycles, but the quantum computing issue forces the community to look at security from a longer-term structural perspective:
- BlackRock publicly flagged quantum computing as a risk factor in its iShares Bitcoin Trust ETF filing in early 2025, underscoring institutional acknowledgement of this threat.
- Experts debate the timeline: some believe quantum computers capable of compromising Bitcoin could emerge within 2–8 years.
- Others view the threat as more distant, perhaps 10 + years away, and emphasise that upgrades can be made in time.
The bottom line is that while the threat may not be immediate in everyday trading terms, it is real and deserves proactive consideration.
2. Why “Immediate Response” Matters: Technical Imperatives & Consensus Challenges
2.1 The Migration to Quantum-Safe Cryptography: Protocol Obstacles
Addressing the quantum threat isn’t merely a matter of patching software—it requires fundamental changes to the Bitcoin protocol (or other major chains). For instance:
- The introduction of post-quantum signature schemes (such as lattice-based or hash-based digital signatures) would require widespread changes in wallet software, node consensus rules, and infrastructural implementation.
- One academic estimate suggested that to transition Bitcoin safely would require at least 1,827.96 hours (≈ 76 days) of cumulative system-downtime if not planned ahead.
- Meanwhile, companies such as BTQ Technologies have already demonstrated a “quantum-safe Bitcoin” implementation replacing ECDSA with a NIST-approved module-lattice digital signature algorithm (ML-DSA), aiming for network-wide rollout by 2026.
Thus, the longer one waits, the narrower the window for a safe, coordinated transition becomes.
2.2 Balancing Technical Preparedness and Community Consensus
In the case of Bitcoin, protocol updates—especially hard forks—require broad coordination among developers, miners, wallet providers and node operators. The challenge is two-fold:
- Speed: The quantum threat may progress faster than anticipated; recent Google breakthroughs suggest required resources for cryptographic attacks may be falling faster than previously assumed.
- Consensus: The Bitcoin community tends to favour conservatism in protocol changes; altering signature algorithms, upgrading address formats, and phasing out exposed public-key addresses will require aligned action across many stakeholders.
In other words, Bitcoin cannot simply wait until the moment the threat becomes urgent. By then the transition may be chaotic or incomplete, thereby risking a security event.
3. Implications for Japanese Investors: Abandoning the “Forever Asset” Myth and Planning Risk-Hedging
3.1 Recognising the Risk of Technological Evolution
Many Japanese investors view Bitcoin as a permanent “digital gold” hedge. However, the quantum computing threat illustrates that no digital asset is immune from technological obsolescence. The assumption that Bitcoin will endure unchanged indefinitely is challenged by structural risks:
- Since roughly one-quarter of all bitcoins are held in addresses whose public keys are already exposed, the risk isn’t purely hypothetical.
- The fact that major institutions like BlackRock and governments such as El Salvador are already taking preventive measures underlines the seriousness of the threat. El Salvador moved approximately 6,274 BTC (~US$678 million) into 14 separate wallets in August 2025 explicitly due to quantum fears.
Thus, Japanese investors must integrate “technological threat” into their long-term strategy, not treat Bitcoin as a “safe forever” asset without caveats.
3.2 Embedding “Technological Risk” into Portfolio Design
For those seeking new crypto assets, income opportunities and blockchain use cases, the quantum risk opens up strategic pathways:
- Consider diversifying into cryptos or platforms designed with quantum-resistance in mind (for example Quantum Resistant Ledger, QRL) as a hedge.
- Within Bitcoin holdings, limit concentration risk; a portfolio overly skewed to BTC may ignore the possibility that its security assumptions are breached.
- Stay abreast of developments in post-quantum cryptography, protocol-upgrade schedules, and how major ecosystems (Bitcoin, Ethereum, etc.) respond. Having insights into the progress of community readiness is critical.
- Treat Bitcoin not as a static asset but as one that may require significant “upgrade risk” or network transition risk in the medium term.
4. What Investors Can Do Today: Self-Defence Moves for Crypto Holders
4.1 Fundamentals of Wallet Hygiene Against Quantum Exposure
Even before large-scale network upgrades occur, individual holders can take concrete steps to reduce their quantum-attack surface:
- Avoid re-using public keys. Once you broadcast from an address, your public key is revealed and may become vulnerable if quantum computing advances.
- Use wallet addresses that have not revealed their public keys (i.e., stay with P2PKH or P2SH addresses where only the hash has been revealed). Some of the more exposed coins are those sitting in addresses that have already spent (and thus revealed) their public keys.
- When in possession of large holdings, consider migrating coins from older or exposed addresses to “quantum-resilient” addresses (once supported) or addresses with no prior transactions, to reduce risk.
- Regularly monitor developments in quantum-safe cryptography and wallet software updates, since once a protocol transition occurs, older wallets may require migration.
4.2 The Most Important One Step: Audit Your Public-Key Exposure
For many investors, the simplest but most critical step right now is to review your wallet structure and ask: Have I ever spent from a given address? If yes, that address’s public key has been revealed, and thus the risk is non-zero. Even if quantum computers are still immature, the window for response is finite. As one expert put it:
“Within two to eight years, the quantum machine will break the existing elliptic-curve cryptography of Bitcoin.”
Therefore, proactively auditing your wallet addresses and preparing for transition is far better than assuming “we’ll handle it later.”
Conclusion: Time to Embrace “Asset-Backed Representation” and “Autonomous Trust Tender” in the Two-Extremes Model
In line with the framework you’ve developed in your white paper—the “Two-Extremes Model” wherein one extreme is Asset-Backed Representation (traditional finance extension) and the other is Autonomous Trust Tender (decentralised value based on blockchain)—the quantum-computing threat highlights how the trust layer underlying decentralized assets is not static. Even in the autonomous trust model, the cryptographic assumptions can be challenged by technological evolution.
For Bitcoin, often viewed as the leading example of autonomous trust tender, the quantum threat forces a reconsideration of its “immortality”. It doesn’t mean immediate doom, but it does mean the narrative must adjust: security is not an immutable given, but a function of evolving cryptography, community action, and investor awareness.
For practitioners and investors alike, the path forward is clear:
- Monitor the progress of quantum computing and post-quantum implementations.
- Evaluate your holdings and structure with the possibility of cryptographic transition in mind.
- Incorporate the risk of protocol upgrades, wallet migration and technological disruption into your asset allocation.
- Recognize that, in the long term, true resilience means preparedness—and preparedness begins now.
If you like, I can also produce a bespoke graph or figure illustrating timelines of quantum-threat readiness, or highlight specific altcoins designed for quantum-resistance with investment potential. Would you like that?
