VPN Works 0.10.0 signs the Ledger. The kernel holds a signing key, one per machine, and signs each checkpoint and the end of a run’s sealed record; Ledger asks for signatures through a new sign permission and never sees the key. Anyone with the public key can check a ledger with vpnw verify --key.
In the tests, a real run’s ledger with one event changed after its first checkpoint and the whole hash chain computed again failed at checkpoint 2. Stripped signatures, a ledger re-signed with another key and one written unsigned failed too. The untouched ledger checked out on a second machine given only the public key.
Two rounds of independent review found six problems, all fixed with tests. The release post has the details and the limits. Open source, with releases for Linux and macOS.