diff --git a/src/util/string-helper.hpp b/src/util/string-helper.hpp
index de0c41f..14f499e 100644
--- a/src/util/string-helper.hpp
+++ b/src/util/string-helper.hpp
@@ -16,6 +16,29 @@
 static const char *WHITESPACE_CHARS = " \n\r\t";
 
 /**
+ * Return the hex representation of the bytes in array.
+ * @param array The array of bytes.
+ * @return Hex string.
+ */
+inline std::string 
+toHex(const uint8_t* array, size_t arraySize)
+{
+  if (!&array)
+    return "";
+  
+  std::ostringstream result;
+  result.flags(std::ios::hex | std::ios::uppercase);
+  for (size_t i = 0; i < arraySize; ++i) {
+    uint8_t x = array[i];
+    if (x < 16)
+      result << '0';
+    result << (unsigned int)x;
+  }
+
+  return result.str();
+}
+
+/**
  * Modify str in place to erase whitespace on the left.
  * @param str
  */
diff --git a/src/util/time.hpp b/src/util/time.hpp
index 5d729d9..e0b3727 100644
--- a/src/util/time.hpp
+++ b/src/util/time.hpp
@@ -12,6 +12,17 @@
 
 namespace ndn {
 
+/**
+ * A time interval represented as the number of milliseconds.
+ */
+typedef int64_t Milliseconds;
+   
+/**
+ * The calendar time represented as the number of milliseconds since 1/1/1970.
+ */
+typedef int64_t MillisecondsSince1970;
+
+
 const boost::posix_time::ptime UNIX_EPOCH_TIME =
   boost::posix_time::ptime (boost::gregorian::date (1970, boost::gregorian::Jan, 1));
 
@@ -30,6 +41,11 @@
   return getNowMilliseconds();
 }
 
+inline MillisecondsSince1970
+getNow()
+{
+  return getNowMilliseconds();
+}
 
 /**
  * Convert to the ISO string representation of the time.