--- a/services/common/utils.js
+++ b/services/common/utils.js
@@ -208,17 +208,25 @@ this.CommonUtils = {
     return bytes.map(byte => String.fromCharCode(byte)).join("");
   },
 
   stringToByteArray: function stringToByteArray(bytesString) {
     return Array.prototype.slice.call(bytesString).map(c => c.charCodeAt(0));
   },
 
   bytesAsHex: function bytesAsHex(bytes) {
-    return Array.prototype.slice.call(bytes).map(c => ("0" + c.charCodeAt(0).toString(16)).slice(-2)).join("");
+    let s = "";
+    for (let i = 0, len = bytes.length; i < len; i++) {
+      let c = (bytes[i].charCodeAt(0) & 0xff).toString(16);
+      if (c.length == 1) {
+        c = "0" + c;
+      }
+      s += c;
+    }
+    return s;
   },
 
   stringAsHex: function stringAsHex(str) {
     return CommonUtils.bytesAsHex(CommonUtils.encodeUTF8(str));
   },
 
   stringToBytes: function stringToBytes(str) {
     return CommonUtils.hexToBytes(CommonUtils.stringAsHex(str));