diff --git a/src/main/java/io/twentysixty/sa/client/util/Aes256cbc.java b/src/main/java/io/twentysixty/sa/client/util/Aes256cbc.java
index e4ad753..3de2893 100644
--- a/src/main/java/io/twentysixty/sa/client/util/Aes256cbc.java
+++ b/src/main/java/io/twentysixty/sa/client/util/Aes256cbc.java
@@ -59,6 +59,6 @@ private static String randomKey(int size) throws Exception {
     KeyGenerator keyGen = KeyGenerator.getInstance(alg);
     keyGen.init(size * 8);
     SecretKey secretKey = keyGen.generateKey();
-    return ISOUtil.dumpString(secretKey.getEncoded());
+    return ISOUtil.hexString(secretKey.getEncoded());
   }
 }