量子コンピューティングの暗号リスク: 今すぐ収穫し、後で説明する復号化

Frequently asked questions

What is the harvest now decrypt later attack?

Harvest now decrypt later (HNDL) is an attack strategy where adversaries capture and store encrypted data today with the intent of decrypting it when quantum computers become powerful enough to break the encryption. For cryptocurrency, this means recording ECDSA signatures and exposed public keys from public blockchains. The harvested data sits in storage until a quantum computer running Shor's algorithm can derive private keys from those public keys. The attack is devastating because blockchain data is public, permanent, and self-documenting.

What is the quantum computing crypto risk?

The quantum computing crypto risk is the mathematical certainty that Shor's algorithm running on a fault-tolerant quantum computer will break the elliptic curve cryptography (ECDSA secp256k1, Ed25519) used by Bitcoin, Ethereum, Solana, and nearly every other cryptocurrency for transaction signing. This is not a theoretical possibility. It is a proven mathematical result. The only uncertainty is the timeline for hardware capable of running the algorithm at scale. In March 2026, Google Quantum AI, working with the Ethereum Foundation and Stanford, compiled Shor against secp256k1 down to 1,200 to 1,450 logical qubits fitting inside fewer than 500,000 physical qubits and finishing in minutes. Nobody knows when; hardware roadmaps reach the needed scale between 2028 (IonQ, on paper) and 2033 (IBM Blue Jay).

Who is harvesting cryptocurrency data right now?

Nation-state intelligence agencies, advanced persistent threat (APT) groups, and well-funded criminal organizations are the primary actors harvesting encrypted data for future quantum decryption. Leaked documents from the NSA, GCHQ, and other agencies have confirmed mass data collection programs. Blockchain data is uniquely vulnerable because it does not need to be intercepted. It is publicly broadcast, globally replicated, and permanently stored by design. Anyone with a full node has a complete copy of every Bitcoin transaction ever made.

How does harvest now decrypt later affect Bitcoin specifically?

Bitcoin is acutely vulnerable to harvest now decrypt later because every spent transaction permanently exposes the sender's secp256k1 public key on the blockchain. As of May 2026, Glassnode counts 6.04 million BTC, 30.2 percent of the entire supply and roughly 469 billion dollars, sitting in addresses with exposed public keys: 1.92 million BTC structurally exposed in P2PK outputs and 4.12 million BTC operationally exposed through address reuse. These public keys are already harvested. When a quantum computer runs Shor's algorithm, each exposed public key yields the corresponding private key. The attacker then signs transactions stealing all remaining funds from those addresses. The harvest is complete. Only the decryption phase remains.

Can I protect my crypto from harvest now decrypt later attacks?

On ECDSA-based chains like Bitcoin and Ethereum, you can reduce exposure by moving funds to fresh addresses whose public keys have never been revealed through a prior transaction. However, this is a temporary measure. The moment you spend from that address, your public key is exposed again. True protection requires moving to a blockchain that uses post-quantum cryptography for transaction signing, specifically SPHINCS+ (NIST FIPS 205) and Kyber-768 (NIST FIPS 203). SynergyX implements both from genesis with no legacy ECDSA attack surface.

What is cryptographic salt and how does SPHINCS+ use it?

Cryptographic salt is random data added to the input of a cryptographic function to ensure that identical inputs produce different outputs. SPHINCS+ uses cryptographic salt in its Merkle tree hash construction to prevent precomputation attacks. Without salt, an attacker could build rainbow tables mapping hash outputs to inputs and use them to forge signatures faster. With salt, each signature computation is uniquely randomized, making precomputation infeasible. This salt hardening is one reason SPHINCS+ is considered the most conservative post-quantum signature scheme.

Is the quantum threat to crypto real or just hype?

The quantum threat to crypto is mathematically real. Shor's algorithm provably breaks ECDSA, Ed25519, RSA, and all elliptic-curve-based cryptography. This is not disputed by any credible cryptographer. The only debate is when the hardware will exist to run it at scale. NIST concluded the threat was real enough to finalize post-quantum standards in 2024. IBM, Google, and PsiQuantum are racing to build machines with sufficient qubits: the IBM roadmap targets roughly 200 logical qubits with Starling in 2029 and over 2,000 logical qubits with Blue Jay in 2033, against a benchmark of 1,200 to 1,450 logical qubits to break secp256k1. The US government has mandated federal agencies begin transitioning to post-quantum cryptography. This is not hype. It is institutional consensus.

How does Kyber-768 protect against harvest now decrypt later?

Kyber-768 (NIST FIPS 203) is a lattice-based key encapsulation mechanism that generates shared secrets using the Module Learning With Errors problem. Unlike ECDH key exchange, which Shor's algorithm breaks, Kyber-768 key exchanges cannot be retroactively decrypted by quantum computers. Data protected by Kyber-768 today has no known quantum decryption path, which blunts harvest-now-decrypt-later. SynergyX uses Kyber-768 for all key exchanges, meaning captured SynergyX traffic has no quantum decryption path.