Challenge-response cable set-top-box system to securely authenticate software application program interfaces (APIs)
View Patent ↗A system for securely authenticating software Application Program Interfaces (APIs) includes a handshake protocol provided between a Conditional Access System (CAS) and Middleware running on a Set-Top-Box. The handshake is a Challenge-Response protocol that includes several steps. The CAS or the Middleware can either act as a Claimant or Verifier in Challenge-Response process. First, a Claimant sends a request to a Verifier requesting access to a function F through the API. The Verifier reacts to the request by outputting a Challenge that is sent to the Claimant The Challenge is also retained by the Verifier for use in its internal calculation to verify the Claimant's response. The Claimant next processes the Challenge using components under a patent License Agreement, known as Hook IP, and issues a Response to the Verifier. The Verifier can then verify the Response to allow the Claimant access to the API.
1. A method for providing handshaking between a (Conditional Access System) CAS application program, middleware and a set top box to allow secure access to an Application Program Interface (API), the secure access being controlled by the CAS, the method comprising:
submitting by middleware a request for support service from the CAS in order to facilitate access of the CAS content by a subscriber;
receiving from the CAS a challenge comprising a random number or a non-repeating numerical value that had not been previously used by the CAS;
calculating a challenge response using a function over the challenge value using the middleware, where that function is controlled by intellectual property (IP) rights and referred to here as Hook IP, and wherein the calculated output of said function is provided as a response from the middleware to the CAS; and
returning an acknowledgement from the CAS to the middleware when the response is verified indicating that the support service for accessing the API is enabled.
2. The system of claim 1 , wherein after the CAS has granted access to CAS support service APIs to the middleware, the CAS proceeds to provide keys for use by a SoC or other component in the set-top-box by making corresponding API calls to the Middleware.
3. The system of claim 1 , wherein the middleware is an EPG Application that provides a program guide after the acknowledgement is returned from the CAS to the EPG middleware indicating the support service of the CAS is enabled after the Challenge and Response.
4. The system of claim 1 , wherein in calculating the response, the middleware determines if a License Agreement has been executed by an app provider for the specific API to access content for a channel of the set-top-box.
5. A method for providing handshaking between a (conditional access system) CAS application program, middleware and a set top box to allow secure access to an Application Program Interface (API), the secure access being controlled by the middleware, the method comprising:
by the CAS a request to the middleware to access content decryption related APIs used by the CAS;
receiving from the middleware at the CAS a challenge including a random number or a non-repeating numerical value that has not been used by the middleware;
calculating a function over the challenge value in the CAS, where that function is controlled by intellectual property (IP) rights and referred to here as Hook IP, and wherein the output of the calculated function is provided as a response from the CAS to the middleware; and
receiving an acknowledgement at the CAS provided by the middleware when the response is verified by the middleware indicating that content decryption related APIs are enabled.
6. The method of claim 5 , wherein as part of the received acknowledgement, the middleware also returns an API handle or token that the CAS may subsequently pass to the middleware in order to prove it has been authorized.
7. The method of claim 6 , wherein the API handle or token is an encrypted value that can only be decrypted and verified by the middleware.
8. The method of claim 5 , wherein an encrypted content comes into the set top box from a cable head end.
9. The method of claim 8 , wherein decryption keys are also delivered by the cable head end to the CAS to enable decryption of data received.
10. The method of claim 9 ,
wherein the CAS passes the decryption keys, which are encrypted, to a System on a Chip (Soc) or other hardware device in the set top box via the middleware, and
wherein the middleware will pass the decryption keys to the Soc or other hardware device along with the API Handle or token after the step of verifying by the middleware.
11. The system of claim 5 , wherein the response from the CAS is calculated as:
Response=F(Challenge, APP-Class), wherein the function F( ) Challenge value is the calculated challenge value, and wherein the function F( ) APP-Class value indicates what data class content available through one of the APIs for the channel the set top box will be allowed access to.
12. The system of claim 11 , wherein in calculating the response, the CAS determines if an agreement has been executed by an app provider for a specific APP-Class, and if the agreement has been executed for the specific APP-Class, the CAS will obtain corresponding secret parameters for accessing the API identified by the specific APP-Class for computing the response.
13. The system of claim 11 , wherein for the APP-Class, CAS Applications are given one set of secret parameters, while applications with access to user private data have a different set of secret parameters.
14. The method of claim 11 , wherein in the verification check by the middleware for the Response and the App Class, the middleware further has to check permissions or restrictions for the specific set-top-box device.
15. The method of claim 14 , wherein during the check of permissions or restrictions for the specific set-top-box, the middleware must provide a request to an external service for the device.
16. The method of claim 14 , wherein during the check of permissions or restrictions for the specific set-top-box, the middleware looks up authorizations from an object file or a file that has been delivered from an external server.