Which of the following best defines encryption?

Encryption is best defined as the process of transforming information to make it unreadable without a key. This means that original data is converted into a format that is not understandable to unauthorized users, providing a layer of security for sensitive information. The transformation often employs algorithms that rearrange or obscure the data, requiring a specific key or method to revert it back to its original, comprehensible state. This ensures that only individuals with the appropriate key can access the readable version of the data, thereby protecting it from unauthorized access.

The other choices refer to different concepts in data management and security. Compressing data to save storage space relates to reducing the size of files for efficient storage, but it does not involve making data unreadable. The act of converting data back to its original form pertains to decryption, which is the reverse process of encryption but does not describe encryption itself. Lastly, detecting changes in file integrity usually involves checksums or hash functions, which are methods for verifying that data has not been altered; this is not related to the transformation of data into an unreadable format.