This paper presents a new way for applying a CryptoComputing method that prevents some types of attack from malicious hosts against mobile agents running on them. This method addresses the protection of the interaction protocol of each agent. In this method, encryptions of agent interaction protocols by individual keys are achieved to prevent eavesdropping by malicious hosts, while retaining the hosts? capability to execute the interaction. The method also introduces integrity check procedures to prevent such tampering as cut and paste and replay attacks by malicious hosts. We show a basic framework with which this CryptoComputing method functions and introduce a modified ElGamal encryption having a special matching function that enables this method.