Calls from an application in an emulated environment to a module in the operating system hosting the emulated environment may be combined to reduce the overhead of accessing the module. An application handling secure shell (SSH) communications may execute multiple calls to a cryptographic module in the host operating system. Because many calls to the cryptographic module during SSH communications follow patterns, two or more related calls may be combined into a single combined call to the cryptographic module. For example, a call to generate a server-to-client key and a call to generate a client-to-server key may be combined into a single call.