KEM Question about restoring encapsulated secret by decapsulation

[sungmin-net]

Dear OQS team,
I'm newbie in OQS then please understand my questions.

I tried the sample KEM code in "https://openquantumsafe.org/liboqs/examples/kem.html".
In my understanding, the variable 'shared_secret_d' should have same value with the variable 'shared_secret_e' after OQS_KEM_frodokem_640_aes_decaps() because the variable 'ciphtertext' is the encapsulated value for 'shared_secret_d'.

In my trial, I gave 0xC0, 0xC1, 0xC2, ... , 0xCF to 'shared_secret_e' and printed 'shared_secret_d' after OQS_KEM_frodokem_640_aes_decaps(). I expected that 'shared_secret_d' has 0xC0, 0xC1, 0xC2, ... , 0xCF but printing 'shared_secret_d' showed 0xCA, 0xB9, 0x43, 0x43, 0x32, 0x28, 0x29, 0xEB, 0x81 , 0x94, 0x73, 0xB2, 0x1C, 0x1B, 0x0E, 0x2B.

Would you please let me know how I can restore original value 0xC0, 0xC1, 0xC2, ... , 0xCF after decapsulation?

Thanks in advance,
Sungmin.

[baentsch]

Can you please share the complete code you're running? Looking at this statement

In my trial, I gave 0xC0, 0xC1, 0xC2, ... , 0xCF to 'shared_secret_e' and printed 'shared_secret_d' after OQS_KEM_frodokem_640_aes_decaps().

it seems you are not using encaps/decaps as a pair (as it needs to be). See a complete example highlighting identity test here.

[sungmin-net]

Thank you very much @baentsch
I misunderstood that shared_secret_e is an input value for encaps() API to produce ciphertext.
Now I understand that shared_secret_e is output value from encaps() API and decaps() makes shared_secret_d to be same with shared_secret_e using the ciphertext.
Thanks again!