What method enables an application to protect its own data at rest according to Vault principles?

The method that enables an application to protect its own data at rest according to Vault principles is key management and high-level cryptographic offload. Vault focuses on managing secrets and protecting sensitive data through secure means, such as encryption. By leveraging a robust key management system, applications can manage encryption keys securely, ensuring that sensitive data remains protected.

Cryptographic offload refers to delegating the encryption and decryption processes to Vault rather than handling them within the application directly. This reduces the risk of exposing keys and sensitive data to the application layer, which can be more vulnerable to attacks. Therefore, using Vault for key management and cryptographic processes enhances an application's security posture by centralizing control, reducing complexity, and lowering the risk of key leakage.

In contrast, the other options do not align with the principles and functionalities provided by Vault for securing data at rest. Physical security measures and user training programs, while important, are not methods directly related to the operational capabilities of Vault. Downloading data to local storage does not offer protection to that data; instead, it could increase vulnerability if the local storage is not securely managed. Thus, the optimal approach according to Vault principles is to utilize key management and cryptographic offload.