psa_destroy_key: return SUCCESS on an empty slot
Do wipe the slot even if it doesn't contain a key, to erase any metadata.
diff --git a/include/psa/crypto.h b/include/psa/crypto.h
index c880586..982cca7 100644
--- a/include/psa/crypto.h
+++ b/include/psa/crypto.h
@@ -539,7 +539,17 @@
size_t data_length);
/**
- * \brief Destroy a key.
+ * \brief Destroy a key and restore the slot to its default state.
+ *
+ * This function destroys the content of the key slot from both volatile
+ * memory and, if applicable, non-volatile storage. Implementations shall
+ * make a best effort to ensure that any previous content of the slot is
+ * unrecoverable.
+ *
+ * This function also erases any metadata such as policies. It returns the
+ * specified slot to its default state.
+ *
+ * \param key The key slot to erase.
*
* \retval PSA_SUCCESS
* The slot's content, if any, has been erased.