Which method can be employed to ensure data confidentiality?

Encryption is a critical method for ensuring data confidentiality. By transforming readable data into an unreadable format using cryptographic algorithms, encryption protects sensitive information from unauthorized access. Only individuals or systems that possess the correct decryption key can convert this encrypted data back into its original form, thus maintaining the confidentiality of the information.

In contrast, while compression is aimed at reducing the size of data for efficient storage or transmission, it does not inherently protect the data's confidentiality. Redundancy refers to the duplication of critical systems or data to ensure reliability and availability, rather than protecting confidentiality. Logging generally involves creating records of system activity, which is important for auditing and monitoring but does not directly address the need to keep data confidential. Therefore, encryption is the most effective method among the options listed for ensuring that data remains confidential.