The Active Directory Rights Management Services (AD RMS) Client is a vital software component that acts as the direct bridge between an end-user’s applications and the centralized AD RMS Server Infrastructure.
While the AD RMS server establishes identities, handles overall system licensing, and manages policy templates, it is the client software installed on the local device that executes the actual mathematical encryption, decryption, and hard enforcement of document permissions. Core Roles and Functions
The AD RMS Client functions entirely behind the scenes inside the Windows operating system architecture (via standard libraries like Msdrm.dll or Msipc.dll). It is responsible for five primary operational tasks: 1. Device and User Activation
Machine Certification: The client sends information about the local computer to the AD RMS server’s activation service. It then acquires a unique Security Processor Certificate (SPC). This effectively binds that specific computer to the organization’s trusted RMS security hierarchy.
User Certification: The client requests a Rights Account Certificate (RAC) from the server. This links the employee’s logged-in Active Directory credentials to that specific trusted machine. 2. Persistent Document Encryption (Publishing)
When a user creates a sensitive file (e.g., an Information Rights Management (IRM) protected email or Excel sheet), the client creates a unique symmetric key.
It uses that key to encrypt the content locally on the device.
It attaches an Issuance License (IL) directly into the document’s file header. This ensures that protection stays embedded inside the document permanently—even if the file is copied to an unmanaged flash drive or external cloud storage. 3. License Acquisition (Consumption)
When a recipient opens an encrypted document, the local client automatically intercepts the process.
It reads the embedded header and securely contacts the AD RMS server.
It presents the user’s RAC and requests an End-User License (EUL). 4. Document Decryption
If the server verifies that the recipient is authorized, it securely transmits the decryption key inside the EUL.
The AD RMS client receives this token and decrypts the document in memory so the user can see it. 5. Strict Permission Enforcement
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