Final answer:
To verify if a file's content has been altered, a Digital Signature should be used. It uses public key encryption to verify a hash of the data, ensuring the file's integrity and providing non-repudiation.
Step-by-step explanation:
To determine whether the information in a file has changed, you should use a Digital Signature. A digital signature ensures the integrity of the data. It is created using a private key to encrypt the hash of the data. When a recipient wants to verify that the data has not been altered, they can decrypt the hash with the sender's public key and compare it to the hash they generate from the received data. If the hashes match, it means the data has not been altered since it was signed.
Because digital signatures use public key encryption for verification, they ensure that only the holder of the private key could have signed the data. This also provides non-repudiation since the signer cannot deny the signature without denying the ownership of the private key used to create the signature.
Although digital certificates are related to digital signatures, they are used to validate the identity of the entities involved in the communication, not specifically to verify data integrity. Private key encryption, also known as symmetric encryption, uses the same key for encryption and decryption, and thus does not inherently provide a method for signature verification or non-repudiation.