Defining Authentication:

Authentication is the process of verifying a user's identity to ensure they are who they claim to be.

This is commonly achieved through knowledge factors (passwords), possession factors (tokens), or biometric factors (fingerprints).

Why Other Options Are Incorrect:

Option A (Information secrecy): Focuses on protecting data, not identity confirmation.

Option B (Public key encryption): A method of encryption, not directly tied to user identity verification.

Option D (Authorization): Deals with granting access to resources after authentication.