Clear hash state object once hash is finalized

puer.c

@@ -211,4 +211,8 @@ void finalize_hash(struct hashstate *state, unsigned char hash[32]) {
 	for (size_t i = 0; i < 4; i++) {
 		word2bytes(&hash[i*4 + 16], state->b[i]);
 	}
+
+	// Clear all of the hash state, in case there was sth important
+	// there
+	explicit_bzero(state, sizeof(struct hashstate));
 }