As explained elsewhere, there are multiple levels of security in any type of commercial service deployment. One of the layers, used particularly on live stream implementations, is the periodic rotation (i.e update) of the encryption keys used for video scrambling. Rotation here simply means a change in the base encryption key in use – a new random number generated to replace the prior key. This type of change is often forced on an hourly or daily time boundary when live streaming. One reason for making these periodic changes in a continuous streaming presentation is to force a new license acquisition request from each client – a process that ensures that the client has continuing access to the content as time and content rights change. In a streaming architecture based around continuous content delivery, such as the HTTP Live Streaming (HLS) format, the requirement for a new key, and therefore a new license, is initiated by the content encoder in communication to the DRM service. The change in the encryption of stream being delivered is signaled to the client device at least 3 segment periods before the change actually occurs. This timing is critical and must be sufficient for the client to request and receive a new license (containing the new decryption key) before there is any disruption in the viewing experience. In many ways, this type of key rotation is a parallel to the techniques used in linear broadcast systems where it is important to validate content channel licenses at each and every program boundary and at the start of each billing cycle. One additional term, sometimes used in the same context as key rotation, is key renewal. Key renewal is the periodic re-encoding of on-demand stream content assets to refresh the encryption keys used to protect those assets. Again, the change in the base level video scrambling requires the generation of a new DRM license that is associated with that content asset. Key renewal is used as a hedge against the potential for a brute force cracking of the base AES encryption algorithm used on content – a process that in theory can be achieved with significant time and computing power. Another term to be aware of is “license renewal.” This is where periodically in a stream the player is required to asks for a renewed license to continue playback. If a stream is 60 minutes long, live or vod, the service operator can initially issue a 10 minute DRM license and use the “License renewal” option to have the player call for a new license to continue playback each 10 minute mark. This use case is often tied with validating the concurrent access to a stream to insure the viewer still has access to the content.