A clinical research organization is processing highly sensitive personal data including numerical attributes, from medical trial results. The organization needs to manipulate the data without revealing the contents to data users. This can be achieved by utilizing?
The correct answer is **D. Homomorphic encryption**. Homomorphic encryption allows data to be processed and manipulated while it remains encrypted, ensuring that the contents of the data are not revealed to the data users. This is particularly useful when dealing with highly sensitive personal data, such as medical trial results, where privacy and confidentiality are paramount.