Encryption within process control is a well-established phenomenon that provides data security during various operational procedures. While more common encryption types primarily ensure data safety during transmission, homomorphic encryption provides protection within the evaluation phase, preserving data privacy. Despite the strong privacy protection, security vulnerabilities are still present in cloud-based environments. A critical yet often overlooked issue is the potential for ciphertext modifications, which can be caused by various factors. In our research, we aim to analyze these security challenges by identifying potential vulnerabilities and propose an algorithm for the CKKS cryptosystem, as it is the most commonly used in process control applications, that can detect unauthorized alterations to encrypted data. Our approach enhances the safety of encrypted process control systems, ensuring that computation results remain trustworthy despite potential threats in the cloud environment. We demonstrate the effectiveness of our method in safeguarding homomorphic encryption applications from unauthorized ciphertext manipulation using punctual analysis and experimental validation.