Security you can verify

Hybrid post-quantum cryptography combines a classical algorithm (X25519) with a post-quantum algorithm (ML-KEM-768), so an attacker must break both to compromise the shared secret. StenVault combines the two shared secrets using HKDF-SHA256 to derive a single file-encryption key. This protects against current attacks on the classical side and future quantum attacks on it, without relying on the post-quantum algorithm alone — important because post-quantum standards are newer and have had less time under peer review than classical cryptography.

NIST defines five post-quantum security levels. Level 1 is roughly equivalent to AES-128, Level 3 to AES-192, and Level 5 to AES-256. StenVault uses ML-KEM-768 (Level 3) because it provides a strong margin over Level 1 — where most post-quantum deployments currently sit — while keeping keys and ciphertexts small enough for fast file upload and key wrapping. Level 5 would add another margin at the cost of larger keys and slower operations, with no credible near-term threat that Level 3 would fail to stop.

StenVault has not yet undergone a formal third-party cryptographic audit. In the absence of an audit, the transparency mechanism is the open-source code: every primitive, parameter, and data flow is visible under GPL-3.0 at github.com/StenVault/stenvault. The security whitepaper documents exact algorithms, parameters, and design rationale with direct links to the source files. An independent audit is planned as the user base grows.

Because StenVault uses hybrid encryption, a break in ML-KEM-768 alone does not compromise your files. The classical X25519 component continues to protect the shared secret under its own security assumption, giving you time to migrate to a new post-quantum algorithm. The reverse is also true: if a quantum computer breaks X25519 first, ML-KEM-768 still protects you. This dual-protection property is the reason StenVault chose a true hybrid KEM over single-algorithm post-quantum.

Yes. Grover's algorithm — the best-known quantum attack on symmetric ciphers — reduces the effective security of a symmetric key by roughly half, so AES-256 offers approximately 128 bits of post-quantum security, well above the threshold NIST considers secure. The NSA's Commercial National Security Algorithm Suite 2.0 (CNSA 2.0) includes AES-256 alongside ML-KEM and ML-DSA for classified systems, confirming that AES-256 remains appropriate in a post-quantum world.

An adversary who cannot break today's encryption can still collect encrypted traffic and storage now, then decrypt it later, once a cryptographically relevant quantum computer exists. For sensitive long-lived data — legal documents, medical records, intellectual property, personal archives — encryption needs to be quantum-resistant today, not tomorrow. Deferring the upgrade until quantum computers arrive would be too late for data with a decade or more of confidentiality requirements. StenVault adopts post-quantum cryptography now so files encrypted today stay safe decades from now.

The most visible comparison is Internxt, which states on its homepage: “Internxt uses AES-256 combined with post-quantum Kyber-512.” Based on this description, the two primitives operate at different layers — AES-256 for symmetric file encryption and Kyber-512 for key exchange. Neither backstops the other at the same cryptographic level.

StenVault uses a true hybrid KEM: ML-KEM-768 and X25519 both operate at the key-encapsulation level, and their shared secrets are combined via HKDF-SHA256 before deriving the file-encryption key. An attacker must break both to compromise the shared secret.

The NIST security level also differs. Internxt's own blog describes Kyber-512 as “roughly equivalent to AES-128” (NIST Level 1). StenVault uses ML-KEM-768, which is NIST Level 3 — roughly equivalent to AES-192.

Finally, StenVault includes post-quantum signatures (ML-DSA-65 + Ed25519 hybrid) for file integrity. Internxt has no documented post-quantum signature scheme.