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Post-quantum security

Built for the post-quantum era.

A crypto-agile architecture designed for hybrid classical + post-quantum cryptography, following NIST's post-quantum standards — explained without the hype.

See the architectureSecurity overview
Hybrid key establishmentYour device and the recipient run X25519 and ML-KEM-768 in parallel. Both shared secrets enter a key derivation function to produce one session key.Your deviceRecipient / serviceX25519 · classicalML-KEM-768 · FIPS 203ss₁ss₂ss₁ss₂KDFKDFSession key = KDF(ss₁ ‖ ss₂ ‖ transcript)Breaking one algorithm alone is not enough to recover the key.

The threat

Harvest now, decrypt later.

An adversary can record encrypted traffic today and wait for a cryptographically relevant quantum computer. For credentials and identity data with a long lifetime, that is a present-day risk.

Quantum algorithms affect cryptography unevenly. Shor's algorithm would break today's public-key key exchange and signatures (RSA, elliptic curves). Grover's algorithm offers at most a quadratic speed-up against symmetric ciphers, so AES-256 keeps a large security margin.

That is why ARKCRON concentrates post-quantum work where the risk is: key establishment for sync and sharing, and signatures for device enrollment and policy integrity.

In August 2024 NIST published its first post-quantum standards: FIPS 203 (ML-KEM), FIPS 204 (ML-DSA) and FIPS 205 (SLH-DSA). ARKCRON's design is built around them.

Architecture

Six steps from your device to the vault.

Classical and post-quantum algorithms run side by side. An attacker would need to break both.

Algorithms
PurposeDesign
Symmetric encryptionAES-256-GCM
Password-based KDFArgon2id (RFC 9106)
Key establishmentHybrid X25519 + ML-KEM-768 (FIPS 203)
Digital signaturesHybrid Ed25519 + ML-DSA (FIPS 204)
TransportTLS 1.3 with hybrid PQC key exchange where supported
  1. 01

    User device

    Where your secret and keys live.

  2. 02

    Local encryption

    AES-256-GCM

    Items sealed with AES-256-GCM.

  3. 03

    Key derivation

    Argon2id

    Argon2id derives the key-encryption key.

  4. 04

    Hybrid cryptographic layer

    FIPS 203 · 204

    X25519 + ML-KEM-768 for sharing and sync; Ed25519 + ML-DSA for signatures.

  5. 05

    Encrypted ARKCRON Cloud

    Ciphertext over TLS 1.3, stored encrypted at rest.

  6. 06

    Zero-knowledge vault

    Only your devices can open it.

Crypto agility

Ready to change algorithms without drama.

Standards will evolve. ARKCRON is designed so a migration is a software update, not a data rescue.

Versioned ciphertext

Every blob carries an algorithm and version header, so old and new formats can coexist.

Re-wrappable keys

Keys can be re-wrapped under new algorithms on your device, without you re-entering anything.

Policy-driven algorithms

Algorithm choices come from a signed policy, not hard-coded constants.

Hybrid by default

Post-quantum algorithms are combined with proven classical ones during the transition.

Implementation hygiene

Constant-time libraries, test vectors and independent review before any algorithm ships.

Long-lived data first

Sharing keys and recovery material — data with the longest life — move to hybrid first.

Encrypt for the next decade, not the last one.

Free for individuals. No card required. Your keys stay on your devices from the first minute.

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