A cryptosystem consists of which of the following?

A cryptosystem is a comprehensive framework that encompasses various elements essential for the secure encryption and decryption of data. The correct choice highlights that a cryptosystem consists of the algorithm used for encryption, the keys that secure the information, and all associated plaintexts (the original data before encryption) and ciphertexts (the transformed data after encryption).

This broad inclusion is crucial because the strength and effectiveness of a cryptosystem are not just determined by the encryption algorithm and the keys but also how these components interact with the actual data being encrypted and decrypted. Knowing the plaintexts and ciphertexts helps in assessing the system's vulnerability and overall security posture.

The other options focus on limited components, which does not accurately reflect the full scope of what constitutes a cryptosystem. For instance, mentioning only the algorithms or just the key management omits crucial factors that are pivotal for understanding how data security is maintained in practice. Thus, the full context provided by the correct answer outlines the complete nature of a cryptosystem.