Which statement best describes the function of cryptography?

The function of cryptography is primarily to secure data by making it unreadable to unauthorized individuals. This is achieved through the use of algorithms and keys that transform plain text into an encrypted format, ensuring that only those with the correct key can access or interpret the information. This process protects sensitive information from eavesdropping, tampering, and various cyber threats, thereby maintaining the confidentiality and integrity of the data.

In a broader context, while monitoring network performance, ensuring data availability, and retrieving lost information are important aspects of overall information security and management, they do not directly describe the core purpose of cryptography. Cryptography's primary role revolves around securing data, which is essential in today’s digital landscape where data privacy and security are paramount. Thus, the assertion that cryptography makes data unreadable is a clear and accurate representation of its fundamental function.