API in conjunction with a bridge chip and first and second hosts having first and second memories respectively. The bridge chip connects the memories. The API comprises key identifier registration functionality to register a key identifier for each of plural computer processes performed by the first host, thereby to define plural key identifiers; and/or access control functionality to provide at least computer process P1 performed by the first host with access, typically via the bridge chip, to at least local memory buffer M2 residing in the second memory, typically after the access control functionality first validates that process P1 has a key identifier which has been registered, e.g., via the key identifier registration functionality. Typically, the access control functionality also prevents at least computer process P2, performed by the first host, which has not registered a key identifier, from accessing local memory buffer M2, e.g., via the bridge chip.