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*/
-extern bool prf(const char *secret, size_t secretlen, char *seed, size_t seedlen, char *out, size_t outlen) __attribute__((__warn_unused_result__));
+#include "system.h"
+
+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__));
#endif