Harvest Now, Decrypt Later:
Why Your Secrets Need Quantum-Safe Protection Today

1. Executive Summary

This is not a theoretical risk. Intelligence agencies have publicly acknowledged harvest-now-decrypt-later (HNDL) programs. The data you encrypt today has a shelf life — and for many organizations, that shelf life is shorter than they think.

NIST finalized three post-quantum cryptographic standards in 2024 (FIPS 203, 204, 205). The EU published its Post-Quantum Cryptography Roadmap in June 2025, setting a 2030 deadline for critical infrastructure migration. The window to act is now.

This whitepaper explains the threat, the standards, the regulatory landscape, and provides a practical migration path using QuantumAPI — the European platform for quantum-safe identity, secrets, and encryption.

2. The Quantum Threat to Encrypted Data

Modern encryption relies on two mathematical problems that classical computers cannot solve efficiently:

• RSA / Diffie-Hellman: Integer factorization and discrete logarithm
• ECC (Elliptic Curve): Elliptic curve discrete logarithm

In 1994, mathematician Peter Shor published an algorithm that, running on a sufficiently powerful quantum computer, solves both problems in polynomial time. This means:

Symmetric algorithms like AES-256 are not directly threatened by quantum computers. Grover’s algorithm reduces AES-256 to the equivalent security of AES-128, which remains computationally infeasible. The real vulnerability lies in asymmetric cryptography — the key exchange, digital signatures, and public-key encryption that protect virtually every internet connection and stored secret.

3. Timeline: When Will Quantum Computers Break RSA?

The honest answer: nobody knows exactly. But the estimates are converging:

The critical insight is not the exact year — it’s the data lifespan. If your data needs to remain confidential for 10 years, and quantum computers might break RSA in 5-9 years, then your data is already at risk today.

4. Harvest Now, Decrypt Later: The Attack Model

The Harvest Now, Decrypt Later (HNDL) attack is deceptively simple:

1. Intercept — Capture encrypted traffic and data at rest (via network taps, compromised infrastructure, insider access, or supply chain attacks)
2. Store — Archive the encrypted data. Storage is cheap — a petabyte costs under $20,000/year
3. Wait — Continue collecting until quantum computers are available
4. Decrypt — Run Shor’s algorithm to recover the private keys, then decrypt everything retroactively

This is not speculative. In 2023, the European Parliament’s ITRE Committee acknowledged HNDL as an active threat. The Five Eyes intelligence alliance has explicitly cited this attack model in guidance documents.

The economic calculus is overwhelmingly in favor of the attacker: the cost of storage drops every year, while the value of the data remains constant or increases. There is zero downside to hoarding encrypted data if you believe quantum decryption will eventually be possible.

5. What TLS 1.3 Does Not Protect

A common response we hear: “TLS 1.3 already supports post-quantum key exchange (X25519Kyber768). Problem solved, right?”

Wrong. TLS only protects data in transit — the moment between sending and receiving. Once your data arrives, TLS has done its job and the protection ends. Consider what happens next:

TLS is necessary but not sufficient. Your secrets vault, key management system, and identity platform must independently use post-quantum algorithms to protect data at rest and key material.

6. NIST Post-Quantum Standards

In August 2024, NIST published three post-quantum cryptographic standards after an 8-year evaluation process involving submissions from researchers worldwide:

QuantumAPI implements all three standards via BouncyCastle Cryptography, with ML-KEM-768 as the default key encapsulation mechanism and ML-DSA-65 as the default digital signature algorithm. Data encryption uses AES-256-GCM (symmetric, already quantum-resistant) with keys encapsulated via ML-KEM.

7. EU Regulatory Landscape

The European Union has taken an aggressive stance on post-quantum migration:

Organizations that begin migration now will have a significant compliance advantage. Those that wait until regulations mandate PQC will face rushed, expensive migrations under regulatory pressure.

8. QuantumAPI: Architecture for Quantum-Safe Protection

QuantumAPI is the European platform that provides quantum-safe protection across three layers:

Encryption Architecture

QuantumAPI uses a two-layer envelope encryption model:

1. Data Encryption Key (DEK): Each secret is encrypted with a unique AES-256-GCM key using a QRNG-generated nonce
2. Key Encryption Key (KEK): The DEK is encapsulated using ML-KEM-768, producing a quantum-safe ciphertext that wraps the symmetric key

This means: even if an attacker obtains the encrypted data and the wrapped DEK, they cannot recover the plaintext without breaking ML-KEM — which is designed to resist quantum attacks at NIST Security Level 3.

Quantum Random Number Generation (QRNG)

Cryptographic security depends on the quality of randomness. Classical pseudo-random number generators (PRNGs) are deterministic — given enough output, the internal state can theoretically be reconstructed.

QuantumAPI uses real quantum random numbers generated by Quantum Blockchains quantum hardware located in Poland (EU). This provides true entropy derived from quantum mechanical phenomena, ensuring nonces and key material are genuinely unpredictable.

EU Sovereignty

All QuantumAPI infrastructure runs on Scaleway (French cloud provider) in EU data centers. No data is processed or stored outside the European Union. There are no dependencies on US cloud providers (AWS, Azure, GCP) for any customer data processing.

9. Practical Migration Guide

Migrating to post-quantum cryptography does not require replacing your entire stack overnight. Here is a pragmatic, phased approach:

10. Conclusion & Call to Action

The harvest-now-decrypt-later threat is real, active, and growing. Every day that passes, more encrypted data is being collected by adversaries who are patient enough to wait for quantum decryption.

The good news: the solution exists today. NIST standards are finalized. EU regulations are clear. And QuantumAPI provides a complete, European platform to migrate your identity, secrets, and encryption to post-quantum cryptography — without rebuilding your stack.