HSM Cryptographic Key Sharding Enclave

A hardened, constant-time C++20 threshold-signing system. Its defining property: the complete private key is born split across n nodes and is never reconstructed — not at generation, not at signing, not at backup. Any quorum of t nodes jointly produces a standard, externally-verifiable signature (Ed25519 or ECDSA/secp256k1) without the whole key ever existing in any address space.

The security thesis is single-failure containment. A trusted-execution break is treated as realistic, not impossible — and because no node holds a usable key, one compromised node, even a leaked enclave, is not a key compromise. Signing is gated by hardware attestation woven into the protocol itself: every message is cryptographically bound to a fresh, attested session key, so a non-attested node cannot participate in a signing round.

Delivered as source: ~3,600 lines of core C++, ~90 adversarial tests green on two compilers, and an assurance toolchain — independent constant-time verifiers, fuzzing, sanitizers, and binary hardening — held to a bar above commercial norms. Every security property ships with a test that attacks it.