diff --git a/tools/binman/README.entries b/tools/binman/README.entries
index 31bc725..5cb52a9 100644
--- a/tools/binman/README.entries
+++ b/tools/binman/README.entries
@@ -546,6 +546,11 @@
     - kernelkey: Name of the kernel key to use (inside keydir)
     - preamble-flags: Value of the vboot preamble flags (typically 0)
 
+Output files:
+    - input.<unique_name> - input file passed to futility
+    - vblock.<unique_name> - output file generated by futility (which is
+        used as the entry contents)
+
 Chromium OS signs the read-write firmware and kernel, writing the signature
 in this block. This allows U-Boot to verify that the next firmware stage
 and kernel are genuine.
diff --git a/tools/binman/entry.py b/tools/binman/entry.py
index 77cfab9..e671a2e 100644
--- a/tools/binman/entry.py
+++ b/tools/binman/entry.py
@@ -456,3 +456,21 @@
         if missing:
             raise ValueError('Documentation is missing for modules: %s' %
                              ', '.join(missing))
+
+    def GetUniqueName(self):
+        """Get a unique name for a node
+
+        Returns:
+            String containing a unique name for a node, consisting of the name
+            of all ancestors (starting from within the 'binman' node) separated
+            by a dot ('.'). This can be useful for generating unique filesnames
+            in the output directory.
+        """
+        name = self.name
+        node = self._node
+        while node.parent:
+            node = node.parent
+            if node.name == 'binman':
+                break
+            name = '%s.%s' % (node.name, name)
+        return name
diff --git a/tools/binman/entry_test.py b/tools/binman/entry_test.py
index 6fa735e..4100bcc 100644
--- a/tools/binman/entry_test.py
+++ b/tools/binman/entry_test.py
@@ -54,6 +54,17 @@
         self.assertIn("Unknown entry type 'invalid-name' in node "
                       "'invalid-path'", str(e.exception))
 
+    def testUniqueName(self):
+        """Test Entry.GetUniqueName"""
+        import entry
+        Node = collections.namedtuple('Node', ['name', 'parent'])
+        base_node = Node('root', None)
+        base_entry = entry.Entry(None, None, base_node, read_node=False)
+        self.assertEqual('root', base_entry.GetUniqueName())
+        sub_node = Node('subnode', base_node)
+        sub_entry = entry.Entry(None, None, sub_node, read_node=False)
+        self.assertEqual('root.subnode', sub_entry.GetUniqueName())
+
 
 if __name__ == "__main__":
     unittest.main()
diff --git a/tools/binman/etype/vblock.py b/tools/binman/etype/vblock.py
index 595af54..c4d970e 100644
--- a/tools/binman/etype/vblock.py
+++ b/tools/binman/etype/vblock.py
@@ -25,6 +25,11 @@
         - kernelkey: Name of the kernel key to use (inside keydir)
         - preamble-flags: Value of the vboot preamble flags (typically 0)
 
+    Output files:
+        - input.<unique_name> - input file passed to futility
+        - vblock.<unique_name> - output file generated by futility (which is
+            used as the entry contents)
+
     Chromium OS signs the read-write firmware and kernel, writing the signature
     in this block. This allows U-Boot to verify that the next firmware stage
     and kernel are genuine.
@@ -53,8 +58,9 @@
                 return False
             input_data += data
 
-        output_fname = tools.GetOutputFilename('vblock.%s' % self.name)
-        input_fname = tools.GetOutputFilename('input.%s' % self.name)
+        uniq = self.GetUniqueName()
+        output_fname = tools.GetOutputFilename('vblock.%s' % uniq)
+        input_fname = tools.GetOutputFilename('input.%s' % uniq)
         tools.WriteFile(input_fname, input_data)
         prefix = self.keydir + '/'
         args = [
@@ -69,6 +75,5 @@
         ]
         #out.Notice("Sign '%s' into %s" % (', '.join(self.value), self.label))
         stdout = tools.Run('futility', *args)
-        #out.Debug(stdout)
         self.SetContents(tools.ReadFile(output_fname))
         return True
diff --git a/tools/binman/ftest.py b/tools/binman/ftest.py
index 3f4f5f3..c406555 100644
--- a/tools/binman/ftest.py
+++ b/tools/binman/ftest.py
@@ -1316,7 +1316,7 @@
         """Fake calls to the futility utility"""
         if pipe_list[0][0] == 'futility':
             fname = pipe_list[0][3]
-            with open(fname, 'w') as fd:
+            with open(fname, 'wb') as fd:
                 fd.write(VBLOCK_DATA)
             return command.CommandResult()