extern bool prf(const char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, size_t outlen) __attribute__((__warn_unused_result__));
#endif
extern bool prf(const char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, size_t outlen) __attribute__((__warn_unused_result__));
#endif