Communication Between a CA and a TA

CA and TA API functions are executed as follows:

1. Open a session.

   After a CA calls the TEEC_OpenSession function, the secure OS calls the TA_CreateEntryPoint and TA_OpenSessionEntryPoint functions of the secure service. TEEC_OpenSession uses the TA UUID to establish a session between the CA and TA. Note that the CA must have the same UUID and command ID as the CA.

2. Execute the command.

   After the CA executes the TEEC_InvokeCommand command, the secure OS calls the TA_InvokeCommandEntryPoint API of the secure service. The secure service processes the command delivered by the CA and returns the result.

3. Close the session.

   After the CA calls the TEEC_CloseSession function, the secure OS calls the TA_CloseSessionEntryPoint function of the TA and then the TA_DestroyEntryPoint function of the secure service.

   Figure 1 TA and CA communication process