Mode 2 — PKI Drop-in

Mode 2 is for existing PKI consumers that need to migrate from single-party keys to threshold keys without touching the application layer. The application keeps talking PKCS#11, OpenSSL, JCE, or a TLS callback — Confium translates every operation into a threshold session behind the scenes.

When to choose Mode 2

  • You have an existing TLS terminator, code signer, document signer, KMS, or HSM-backed service.
  • You want threshold-key security without rewriting the consumer.
  • You want to migrate to post-quantum algorithms via composite signatures.

The integration surface

Confium ships four adapters:

Adapter What it speaks What it replaces
confium-pkcs11-server PKCS#11 v3.0 HSM
confium-openssl-provider OpenSSL 3.0 provider OpenSSL EVP_PKEY backend
confium-jce-provider JCE provider Java KeyStore / Cipher / Signature
confium-tls-signer TLS 1.3 signature callback TLS private-key operations

Each adapter exposes the standard API; under the hood it dispatches to a Confium coordinator that runs a threshold session per operation.

Deployment shape

[ Existing consumer ] --- PKCS#11 / OpenSSL / JCE ---> [ Confium adapter ]
                                                                |
                                                                v
                                                        [ Coordinator ]
                                                                |
                                                       [ Party 1 ] [ Party 2 ] [ Party N ]

The consumer doesn’t know about threshold keys, quorum, or sessions. It calls C_Sign() (or EVP_DigestSign(), or Signature.sign()) and gets back a signature. The adapter handles the rest.

Post-quantum migration

Mode 2 is the natural home for PQ migration via composite signatures:

  1. The deployment adds an ML-DSA-65 component to the existing classical algorithm (Ed25519 or ECDSA-P256).
  2. The composite signature is published alongside the existing single-algorithm signature.
  3. Upgraded verifiers check both components; legacy verifiers check only the classical component and continue to accept.
  4. Once all verifiers are upgraded, the classical component can be removed.

This is a software upgrade, not an HSM replacement. No new hardware, no re-issuance of every certificate, no flag day.

See also