Common Interface

Common Interface

Cabot’s Common Interface (CI) solutions are called Hercules and Keystone.

Additional Information


Hercules provides the core CI functionality providing compatibility with CI compliant modules, allowing users to view protected content.  Keystone builds on Hercules, adding support for the latest CI+ compliant modules, providing an enhanced security system which uses key exchange cryptography to protect content across unsecured data links.  The data itself is encrypted with triple-DES or AES-128 algorithms using keys that cycle periodically.  This protects the high value content broadcasters want to offer viewers and means that at no stage in the broadcast, from transmission to display, is unencrypted content accessible. 

Keystone successfully completed a rigorous testing regime based upon CI+ LLP requirements which included tests for:

  • Secure channel negotiation and authentication
  • Diffie-Hellman key exchange
  • Certificate exchange and verification
  • Successful video decryption
  • Application MMI (MHEG) display and interaction


As Cabot recognises the importance of reliable and consistent interoperability between all CI and CI+ products, Keystone is also continually tested with third party test tools such as SmarDTV, Neotion and SMiT and against both legacy and state of the art CAMs from a wide variety of manufacturers.  Keystone is also exercised on a number of different host platforms to ensure consistent interoperability across all deployments.  As Keystone’s architecture enables any platform to be supported, Cabot also maintains a strict testing regime across a range of environments such as STB, DVR and IDTV, as well as hybrid and IPTV solutions.

As part of the testing process Cabot also developed a bespoke CI+ CAM emulator in the Python programming language.  This allowed Cabot to generate custom tests scenarios, including advanced Application MMI (MHEG) interaction using downloadable fonts and data pipes.  The emulator has proved to be hugely valuable in accelerating Cabot's CI+ stack development and was even used to help validate prototype CI+ CAMs.  This has now been integrated into our automated test environment, known as Robotester.

Due to the enhanced CI+ specification profile, Keystone also offers a rich user interface by using MHEG-5 applications.  This enables content providers and CAM manufacturers to present more professional and dynamic interfaces to the user than was possible with the original CI specification.  The downloadable font capability enables better broadcaster branding in the market, and therefore easy differentiation from other providers.  This also means that users benefit from a high quality dynamic user interface that is tailored to the content/CAM provider's offering.  In addition, a range of additional capabilities can be enabled with CI+ driving the solution, including VOD video streaming over a network and live internet widgets.