Rewrite Add_Secret to be more correct
Rewrite Add_Secret to be more correct

Use real routines rather than faking them

cose-wg/COSE-C,cose-wg/COSE-C,cose-wg/COSE-C,hildjj/COSE-C,hildjj/COSE-C,jimsch/COSE-C,jimsch/COSE-C,hildjj/COSE-C,jimsch/COSE-C