This sealing example is only for illustration purpose. It generates a random number inside the enclave and calls the sealing api to seal it. Then it unseals the sealed data structure to verify the number. Code is available at https://github.com/sangfansh/SGX101_sample_code.
Original unmodified version is at https://github.com/digawp/hello-enclave.
The application first initializes the enclave in the main function. Then it makes an ECall into the enclave to generate a random number (a fake random number just for simplicity).
In order to seal the number, the application first has to allocate memory for sealed data block (line 30 at App.cpp). Then it makes another ECall into the enclave to seal the random secret.
The seal() function is an ECall wrapper function of the trusted SGX sealing api. It passes the required parameters into function sgx_seal_data() provided by SGX SDK (Sealing.cpp). If this ECall returns successfully, the random secret will be securely sealed in (sgx_sealed_data_t*)sealed_data.
After the random secret is successfully sealed, the application makes another ECall unseal() to unseal the sealed_data. Function unseal() is also a wrapper function of the trusted SGX sealing api sgx_unseal_data(). If this ECall returns successfully, the unsealed content of sealed_data will be stored into int unsealed.
Finally the application verifies the result by printing out and comparing the unsealed secret with the original generated random number (line 50 at App.cpp).
To compile and run this example, run make inside the example directory and type ./app to run the application. It should produce some output like this: