Security APIs are used to define the boundary between trusted and untrusted code. The security properties of existing API are not always clear. In this paper, we give a new generic API for managing symmetric keys on a trusted cryptographic device. We state and prove security properties for the API. In particular, our API offers a high level of security even when the host machine is controlled by an attacker. Our API is generic in the sense that it can implement a wide variety of (symmetric key) protocols. As a proof of concept, we give an algorithm for automatically instantiating the API commands for a given key management protocol. We demonstrate the algorithm on a set of key establishment protocols from the Clark-Jacob suite.