-extern bool prf(const char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, size_t outlen) __attribute__ ((__warn_unused_result__));
+extern bool prf(const uint8_t *secret, size_t secretlen, uint8_t *seed, size_t seedlen, uint8_t *out, size_t outlen) __attribute__((__warn_unused_result__));