--- loncom/interface/loncommon.pm	2016/08/07 20:56:23	1.1075.2.105
+++ loncom/interface/loncommon.pm	2016/08/11 00:15:06	1.1075.2.106
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common routines
 #
-# $Id: loncommon.pm,v 1.1075.2.105 2016/08/07 20:56:23 raeburn Exp $
+# $Id: loncommon.pm,v 1.1075.2.106 2016/08/11 00:15:06 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -16264,11 +16264,19 @@ sub des_decrypt {
     } else {
         $cypher=new DES $keybin;
     }
-    my $plaintext=
-        $cypher->decrypt(unpack("a8",pack("H16",substr($cyphertext,0,16))));
-    $plaintext.=
-        $cypher->decrypt(unpack("a8",pack("H16",substr($cyphertext,16,16))));
-    $plaintext=substr($plaintext,1,ord(substr($plaintext,0,1)) );
+    my $plaintext='';
+    my $cypherlength = length($cyphertext);
+    my $numchunks = int($cypherlength/32);
+    for (my $j=0; $j<$numchunks; $j++) {
+        my $start = $j*32;
+        my $cypherblock = substr($cyphertext,$start,32);
+        my $chunk =
+            $cypher->decrypt(unpack("a8",pack("H16",substr($cypherblock,0,16))));
+        $chunk .=
+            $cypher->decrypt(unpack("a8",pack("H16",substr($cypherblock,16,16))));
+        $chunk=substr($chunk,1,ord(substr($chunk,0,1)) );
+        $plaintext .= $chunk;
+    }
     return $plaintext;
 }