A system, method, and computer program product for establishing mutual trust on a per-deployment basis between two software modules. For example, the first software module may be a Websphere (WS) Information Integrator (II) deployment instance, and the second software module may be a plugin instance. By executing for this deployment an initial handshake between the software modules, both modules identify themselves and exchange digital certificates received from a trusted certification authority and respective public keys. Subsequent communications for this deployment between the software modules proceed with each module encrypting its communications with the public key of the other module; thereby establishing mutual trust between the software modules for each deployment.