The proposed solution does not meet the goal because it recommends using Microsoft-managed keys (MMK). While Azure Storage encryption uses AES-256 by default, the key rotation schedule for MMKs is managed entirely by Microsoft and cannot be configured by the customer to occur on a specific monthly basis. To achieve a user-defined rotation schedule, such as monthly, customer-managed keys (CMK) stored in Azure Key Vault must be used. CMKs provide full control over the key lifecycle, including the ability to rotate keys on demand or on a set schedule by creating a new key version and updating the storage account configuration.

A. Yes: This is incorrect. The solution fails to meet the requirement for a customer-controlled monthly key rotation, as this capability is only available with customer-managed keys (CMK), not Microsoft-managed keys (MMK).

1. Microsoft Learn: Azure Storage encryption for data at rest. Under the section "About encryption key management," it states for Microsoft-managed keys: "Microsoft is responsible for key management, including key creation, rotation, and disabling keys." For customer-managed keys, it states: "You have full control over the key lifecycle, including rotating keys and disabling and revoking access to keys." This distinction is critical to the question.

2. Microsoft Learn: Customer-managed keys for Azure Storage encryption. The section "Rotate customer-managed keys" explicitly details the process: "You can rotate a customer-managed key in Azure Key Vault at any time... To rotate a key, you can create a new version of the key in Azure Key Vault." This confirms that only CMK allows for a user-defined rotation schedule.

3. Microsoft Learn: Encryption scopes for Blob storage. In the "About encryption scopes" section, it clarifies that an encryption scope can use either a Microsoft-managed key or a customer-managed key. However, if configured with a Microsoft-managed key, "Microsoft manages the encryption key," which includes the rotation schedule.