Specification 11 — Mode 2: TC PKI replacement (drop-in)

Definition

Existing PKI consumers (web servers, code signers, email signers, VPN gateways, PKCS#11 applications) replace single-party keys with threshold keys without changing their surrounding ecosystem.

The killer feature: PKCS#11 dispatch

The application sees a normal PKCS#11 token. The PKCS#11 module (confium-pkcs11-server) routes each call to a coordinator, which runs the threshold protocol with the quorum and returns the result.

Existing apps work unchanged:

• OpenSSL (C_Sign, C_Decrypt)
• OpenSSH (agent protocol via PKCS#11)
• Java KeyStore (via JCE provider)
• nginx, Apache (via OpenSSL)
• Any PKCS#11 v3.0 consumer

PQC migration

Mode 2 provides the PQ migration path that doesn’t require replacing HSMs:

1. Today: deploy confium-pkcs11-server with classical algorithm (Ed25519, ECDSA P-256)
2. Tomorrow: software upgrade to composite signatures (classical + PQ)
3. When ecosystem ready: software upgrade to PQ-only

The PKCS#11 interface stays the same throughout. No app re-issuance, no HSM replacement.

Components

Component	Purpose	Status
confium-pkcs11-server	PKCS#11 v3.0 dispatch to threshold	Dispatch layer shipped
confium-openssl-provider	OpenSSL 3.0 provider	Interface
confium-tls-signer	TLS 1.3 signature callback	Interface
confium-jce-provider	Java Cryptography Extension	Interface
confium-composite	Multi-alg composite signatures	Real Ed25519 verifier shipped

Deployment pattern

1. Deploy coordinator service (one per quorum)
2. Deploy Confium share daemons on threshold party machines
3. Install confium-pkcs11-server shared library on app machines
4. Configure app’s PKCS#11 module path
5. App continues working unchanged

Implementation source

• Crates: confium-pkcs11-server, confium-openssl-provider, confium-tls-signer, confium-jce-provider
• Example: confium-examples/src/bin/pkcs11_server_demo.rs