What is the main risk associated with full-disk encryption if the key is not adequately managed?

The main risk associated with full-disk encryption when the encryption key is not adequately managed is indeed data loss. In a scenario where the encryption key is lost or not properly secured, the data on the disk becomes inaccessible. This is because the encryption process renders the data unreadable without the correct key.

If a user or an organization fails to back up the encryption key or loses it due to mismanagement, there is no way to decrypt the data, resulting in irreversible data loss. This risk emphasizes the importance of having robust key management practices, including secure storage of the keys and regular backups.

While unauthorized access, increased processing time, and reduced storage space are considerations in the context of encryption, they do not directly address the critical issue that arises when the encryption key is lost or mishandled. Unauthorized access can occur through other means, increased processing time relates to performance issues rather than data integrity, and reduced storage space is generally a function of the encryption method used rather than a direct risk associated with key management.