diff --git a/src/hash-helper.h b/src/hash-helper.h
index 638a93a..4224860 100644
--- a/src/hash-helper.h
+++ b/src/hash-helper.h
@@ -39,6 +39,7 @@
 public:
   static unsigned char _origin;
   static HashPtr Origin;
+
   Hash (const void *buf, unsigned int length)
     : m_length (length)
   {
@@ -49,18 +50,43 @@
       }
   }
 
+  Hash (const Hash &otherHash)
+  : m_length (otherHash.m_length)
+  {
+    if (m_length != 0)
+      {
+        m_buf = new unsigned char [m_length];
+        memcpy (m_buf, otherHash.m_buf, otherHash.m_length);
+      }
+  }
+
   static HashPtr
   FromString (const std::string &hashInTextEncoding);
 
   static HashPtr
   FromFileContent (const boost::filesystem::path &fileName);
-  
+
   ~Hash ()
   {
     if (m_length != 0)
       delete [] m_buf;
   }
-  
+
+  Hash &
+  operator = (const Hash &otherHash)
+  {
+    if (m_length != 0)
+      delete [] m_buf;
+
+    m_length = otherHash.m_length;
+    if (m_length != 0)
+      {
+        m_buf = new unsigned char [m_length];
+        memcpy (m_buf, otherHash.m_buf, otherHash.m_length);
+      }
+    return *this;
+  }
+
   bool
   IsZero () const
   {
@@ -73,10 +99,27 @@
   {
     if (m_length != otherHash.m_length)
       return false;
-    
+
     return memcmp (m_buf, otherHash.m_buf, m_length) == 0;
   }
 
+  bool operator < (const Hash &otherHash) const
+  {
+    if (m_length < otherHash.m_length)
+      return true;
+
+    if (m_length > otherHash.m_length)
+      return false;
+
+    for (int i = 0; i < m_length; i++)
+      {
+        if (m_buf [i] > otherHash.m_buf [i])
+          return false;
+      }
+
+    return true;
+  }
+
   const void *
   GetHash () const
   {
@@ -88,14 +131,11 @@
   {
     return m_length;
   }
-  
+
 private:
   unsigned char *m_buf;
   unsigned int m_length;
 
-  Hash (const Hash &) { }
-  Hash & operator = (const Hash &) { return *this; }
-  
   friend std::ostream &
   operator << (std::ostream &os, const Hash &digest);
 };