Bio-cryptographic key derivation from cardiac signals

Abstract

We present SOMA, a bio-cryptographic identity system that derives ephemeral cryptographic keys from real-time cardiac electrical signals. Keys exist for the duration of a signing operation (typically < 100ms) and are immediately destroyed. Unlike stored biometrics, SOMA keys are generated fresh from living physiological state, making them resistant to replay attacks, database breaches, and — critically — post-quantum cryptanalysis when combined with lattice-based signature schemes.

Introduction

Digital identity faces two existential threats:

Deepfakes and AI impersonation make knowledge-based and appearance-based identity unreliable
Quantum computing threatens the mathematical foundations of current public-key cryptography

SOMA addresses both by anchoring identity in something that cannot be faked, stolen, or computed: the unique electrical signature of a living human heart, used ephemerally.

Key Derivation Process

ECG Signal → R-peak Detection → Inter-beat Interval Extraction
    → Fuzzy Commitment Scheme → CRYSTALS-Dilithium Key Pair
    → Sign → Destroy Key Material

The critical innovation is the fuzzy commitment scheme that tolerates natural cardiac variation (heart rate changes with activity, stress, time of day) while maintaining cryptographic binding. We use a BCH error-correcting code with parameters tuned to cardiac biometric variance.

Security Properties

Ephemeral by design: Keys exist for < 100ms. Nothing persists to steal.
Liveness guarantee: Dead tissue produces no valid signal. Recorded signals fail the variance check.
Post-quantum: CRYSTALS-Dilithium is a NIST-standardized post-quantum signature scheme.
PUF-equivalent: The heart functions as a biological Physical Unclonable Function.

Open Questions

Long-term cardiac drift: does the fuzzy commitment tolerance hold over years?
Medical conditions that alter ECG morphology significantly
Sensor standardization across consumer hardware

Conclusion