void contrac_get_tracing_key_base64(Contrac const * data, char * base64);
void contrac_set_tracing_key(Contrac * data, unsigned char const * tracing_key);
bool contrac_set_tracing_key_base64(Contrac * data, char const * tracing_key);
void contrac_get_tracing_key_base64(Contrac const * data, char * base64);
void contrac_set_tracing_key(Contrac * data, unsigned char const * tracing_key);
bool contrac_set_tracing_key_base64(Contrac * data, char const * tracing_key);