shared_secret_cache_key
struct shared_secret_cache_key* ssk = (struct shared_secret_cache_key*)k;
size_t key_size = sizeof(struct shared_secret_cache_key)
struct shared_secret_cache_key* ssk = (struct shared_secret_cache_key*)k;
struct shared_secret_cache_key* k =
(struct shared_secret_cache_key*)calloc(1, sizeof(*k));