hardware security module
A tamper-resistant device that keeps keys and signs with them without ever exporting them.
A hardware security module is a tamper-resistant device that generates and stores keys and performs cryptographic operations internally, exposing operations but never the keys themselves.
Examples
The factory CA's private key sits in an HSM, which signs each bench node's certificate without the key ever leaving it.
A stolen provisioning station can't leak the CA key, because the HSM never exports it.