diff --git a/sys/crypto/rijndael/rijndael-api-fst.c b/sys/crypto/rijndael/rijndael-api-fst.c
--- a/sys/crypto/rijndael/rijndael-api-fst.c
+++ b/sys/crypto/rijndael/rijndael-api-fst.c
@@ -63,6 +63,7 @@
 		key->Nr = rijndaelKeySetupDec(key->rk, cipherKey, keyLen);
 	}
 	rijndaelKeySetupEnc(key->ek, cipherKey, keyLen);
+	explicit_bzero(cipherKey, sizeof(cipherKey));
 	return TRUE;
 }