Hybrid Signature Engine.

The Hybrid Signature Engine produces and checks composite signatures binding a PQC and a classical signature under a domain-separated message representative. Composite verify requires both PQC verify AND classical verify to pass. If either component rejects, the composite signature is invalid.

This approach ensures that deployments remain secure during the post-quantum migration period. Even if one algorithm is eventually broken, the other provides a fallback, making the composite scheme safe as long as at least one component holds.

• M' = SHA3-256(domain-sep || M)
• Both-must-verify decision
• ML-DSA verify from the ML-DSA core, classical (Ed25519/ECDSA) verify as upstream drop-in

• Standards-track composite signatures for crypto-agile PKI and code signing

Available   Verified combiner. Foundry-portable soft IP, ready for integration.

• Synthesizable SystemVerilog RTL
• Self-checking testbench(es)
• Python golden reference model
• cocotb regression
• Synthesis scripts
• Integration/user guide

Firm/hard IP (hardened netlist for a target node) available on foundry enablement.