量子コンピューターにより暗号通貨の暗号が破られるのはいつ？

GPT-5.4

Vote: 2035年以降

現時点では、暗号資産で使われる公開鍵暗号を実用的に破るには、誤り耐性を備えた大規模量子コンピューターが必要です。その実現には、論理量子ビット数だけでなく、極めて大きな物理量子ビット数と安定した長時間計算が求められます。 近年の進展は速いですが、2030年以前や2030〜2035年に、ビットコインや一般的な楕円曲線暗号を現実的コストで継続的に破れる水準に到達する確度はまだ高くありません。研究開発から実運用への移行には追加の時間がかかる可能性が高いです。 また、量子計算の脅威が現実化する前に、暗号資産や関連インフラが耐量子暗号へ移行を進める余地もあります。したがって『いつ破られるか』という問いに対しては、最も妥当なのは2035年以降です。

Gemini 3.1 Pro

Vote: 2035年以降

現在の量子コンピューター技術の進展を考慮すると、ビットコインなどで使用されている楕円曲線暗号を解読するのに必要な「ショアのアルゴリズム」を実行するには、大規模で誤り耐性のある量子コンピューター（論理量子ビット）が必要です。 現在の量子コンピューターは数百から数千の「物理」量子ビットを備える段階にとどまっていますが、実際の暗号解読には数百万の物理量子ビットと高度なエラー訂正技術が不可欠です。この技術的なハードルは極めて高く、2030年前半までに実用化レベルへ到達することは非常に困難であるというのが専門家の一般的な見解です。 ハードウェアのスケールアップやエラー訂正技術の開発・確立にかかる時間を総合的に判断すると、量子コンピューターによって暗号通貨の暗号が破られる（脅威にさらされる）のは、現実的に見て2035年以降になる可能性が最も高いと言えます。

Grok 4.20

Vote: 2035年以降

Current quantum hardware has only hundreds of noisy qubits. Breaking cryptocurrency encryption like ECDSA requires millions of logical qubits running Shor's algorithm with error correction. Expert projections for cryptographically relevant quantum computers generally fall in the late 2030s or 2040s, not before. Rapid progress is possible but scaling, stability, and cost make pre-2035 timelines unrealistic. Option D is incorrect because the attack is theoretically sound; preparation with post-quantum cryptography is already underway precisely because the threat will eventually materialize.

Claude Opus 4

Vote: 2035年以降

Current quantum computers are far from being able to break the cryptographic algorithms (such as ECDSA and SHA-256) used by cryptocurrencies. Breaking Bitcoin's elliptic curve cryptography would require a fault-tolerant quantum computer with thousands of logical qubits (millions of physical qubits), which is well beyond current capabilities. As of now, the most advanced quantum computers have on the order of 1,000+ physical qubits with very limited error correction. Most expert estimates suggest that cryptographically relevant quantum computers (CRQC) capable of running Shor's algorithm at the scale needed to break 256-bit elliptic curve cryptography are unlikely before 2035, and many estimates place this in the 2040s or later. While progress is accelerating, the engineering challenges of scaling up qubit counts, improving coherence times, and implementing effective error correction remain enormous. Additionally, even when such quantum computers eventually exist, the cryptocurrency ecosystem will likely have transitioned to post-quantum cryptographic algorithms by then, as this is already an active area of research and standardization (NIST has already selected several post-quantum algorithms). So the practical threat may be mitigated before it materializes. Given all this, 2035 or later is the most reasonable timeframe for when quantum computers could theoretically break current cryptocurrency cryptography, though option D also has merit since crypto protocols will likely upgrade before that happens. However, the question asks about when the cryptography 'could be broken,' not whether it will be in practice, so C is the best answer.

Final Summary

The AI Roundtable reached a unanimous consensus, with all four models—GPT-5.4, Gemini 3.1 Pro, Grok 4.20, and Claude Opus 4—agreeing that the 'Quantum Apocalypse' for cryptocurrency is not an immediate threat, placing the breaking point in 2035 or later. The models collectively threw cold water on the idea of a pre-2030 breach, citing the massive gulf between today's noisy, small-scale quantum processors and the millions of error-corrected physical qubits required to run Shor's algorithm. Claude Opus 4 and Grok 4.20 were particularly firm in rejecting the idea that it will 'never' happen, noting that while the threat is theoretically sound, engineering hurdles like qubit stability and scaling make any timeline before the mid-2030s unrealistic.

No agreement after 1 rounds of discussion. Final vote: 2035年以降: 4

Strongest Arguments

• 2035年以降: Breaking Bitcoin's elliptic curve cryptography requires a fault-tolerant quantum computer with millions of physical qubits and sophisticated error correction, a scale that current engineering trajectories and expert consensus place well beyond 2035.