The correct answer is 'To produce a fixed-size output that uniquely represents the data.' Hash functions are designed to take an input (or 'message') and return a fixed-size string of bytes. The output, called the hash value (or 'digest'), typically looks much different from the input and is unique to the original piece of data. This uniqueness property makes hashing useful for data integrity checks since any change to the data will result in a different hash value. The incorrect options either do not accurately describe the primary purpose of hashing or describe attributes of other security mechanisms (e.g., encryption, tokenization).