What is the primary function of a hash function?

The primary function of a hash function is to ensure data integrity. A hash function takes an input (or message) and produces a fixed-size string of characters, which is typically a digest that represents the data. This process is deterministic, meaning that the same input will always produce the same hash output, allowing users to verify that the data has not been altered or corrupted.

When data is transmitted or stored, a hash can be generated for the original data. If the data is later accessed, the hash can be recalculated and compared to the original hash. If the two hashes match, it confirms that the data remains unchanged, thereby ensuring its integrity. This is crucial in various applications such as file verification, digital signatures, and data integrity checks.

In terms of the other options, while hash functions are related to authentication (by verifying the identity of a data source) and non-repudiation (which can be supported by hashing in digital signatures), their primary purpose focuses on ensuring that the data has not been altered, thereby directly addressing the concept of data integrity. Confidentiality is achieved through encryption, which is unrelated to hashing.