Which of the following best defines cryptography?

Cryptography is fundamentally about securing information, which encompasses various techniques and methodologies used to protect data from unauthorized access and modification. This definition captures the essence of cryptography, emphasizing its primary goal: ensuring confidentiality, integrity, authentication, and non-repudiation of information.

While there are elements of coding messages involved in cryptography, as stated in one of the choices, it's essential to recognize that this is just a part of what cryptography entails. The focus on securing information distinguishes it from merely altering data or coding messages, which could be part of different processes or disciplines in computer science or data handling.

The practice of securing information through cryptographic means often includes algorithms and protocols that encrypt data, making it unreadable to anyone who does not possess the appropriate keys or access rights. This aspect of cryptography is critical for various applications, such as secure communications, data protection, and identity verification.

Ultimately, defining cryptography as the practice of securing information encompasses both its theoretical foundations and practical applications, highlighting its importance in maintaining security in today's digital landscape.