Design a Digital Rights Management (DRM) System

To design a DRM system for a platform like Netflix, I would start by defining the core requirement: delivering high-quality encrypted media while preventing unauthorized redistribution. First, we encrypt all video assets using AES-128 before they enter our storage layer. These assets are distributed via a global CDN to minimize latency. When a user initiates playback, the client app contacts our Authentication Service to verify subscription status. Upon success, the client requests a license from the License Server. This server generates a unique session key, wraps it with the device's public key, and sends it back. Crucially, the private key never leaves the device's Trusted Execution Environment (TEE), ensuring keys cannot be extracted. For revocation, we implement a short-lived token strategy. If a device is compromised, we simply stop issuing new tokens or invalidate existing ones in our database, which the client checks periodically. To ensure scalability, we shard the License Server based on geographic regions and cache frequently requested licenses. We must also handle offline scenarios by allowing temporary local license caching with expiration timers. Finally, we integrate with industry standards like Widevine for Android and FairPlay for Apple to ensure cross-platform compatibility without reinventing the wheel. This architecture balances robust security with the low-latency streaming experience Netflix users expect.