Final answer:
Symmetric-key encryption can be used for message authentication by checking the integrity of a message upon decryption, or through the use of Message Authentication Codes (MACs) like HMAC which uses a secret key to verify the message's authenticity.
Step-by-step explanation:
Symmetric-key encryption can indeed be used to provide message authentication. This is true because symmetric encryption uses the same key for both encrypting and decrypting a message, which means that if a message has been altered during transmission, it will not decrypt correctly. This property can be exploited to verify that a message has not been tampered with, hence providing authentication. Additionally, specific Message Authentication Codes (MACs) can be created using symmetric encryption algorithms to verify the integrity and authenticity of a message.
For example, a Hash-based Message Authentication Code (HMAC) utilizes a cryptographic hash function and a secret symmetric key to generate a value that is appended to the message. When the receiver gets the message and the HMAC, they can use the same secret key to generate an HMAC for the received message. If the generated HMAC matches the received HMAC, this verifies that the message hasn't been altered and that it is authentic.