Techniques are disclosed relating to relating to a public key infrastructure (PKI). In one embodiment, an integrated circuit is disclosed that includes at least one processor and a secure circuit isolated from access by the processor except through a mailbox mechanism. In some embodiments, the secure circuit is configured to generate a public key and a private key for an application, and receive, from the application via an API, a request to perform a cryptographic operation using the private key. The secure circuit is further configured to perform the cryptographic operation in response to the request.