diff --git a/gui/Claim.py b/gui/Claim.py
index 641e351..43c4411 100644
--- a/gui/Claim.py
+++ b/gui/Claim.py
@@ -6,7 +6,7 @@ import Term
 
 class Claim(object):
     def __init__(self):
-        self.id = None          # a unique id string, like 'ns3,r,r3'
+        self.id = None          # a unique id string, consisting of 'protocol,label'
         self.claimtype = None
         self.label = None
         self.shortlabel = None
@@ -36,7 +36,7 @@ class Claim(object):
         self.shortlabel = label
 
         # determine id
-        self.id = "%s,%s,%s" % (self.protocol,self.role,self.shortlabel)
+        self.id = "%s,%s" % (self.protocol,self.shortlabel)
 
         # some additional properties
         if str(self.claimtype) == 'Reachable':
diff --git a/gui/bin/scyther b/gui/bin/scyther
index 971ea52..96dad86 100755
Binary files a/gui/bin/scyther and b/gui/bin/scyther differ
diff --git a/gui/mpa.py b/gui/mpa.py
index 48dc07c..6add6cd 100755
--- a/gui/mpa.py
+++ b/gui/mpa.py
@@ -8,9 +8,16 @@ Test script to execute multi-protocol attacks on some test set.
 
 import Scyther
 
-def MyScyther(protocollist):
+def MyScyther(protocollist,filter=None):
+    """
+    Evaluate the composition of the protocols in protocollist.
+    If there is a filter, i.e. "ns3,I1" then only this specific claim
+    will be evaluated.
+    """
     s = Scyther.Scyther()
-    s.options = "-m2"
+    s.options = "--match=2"
+    if filter:
+        s.options += " --filter=%s" % (filter)
     for protocol in protocollist:
         s.addFile(protocol)
     s.verify()
@@ -20,48 +27,52 @@ def getCorrectIsolatedClaims(protocolset):
     """
     Given a set of protocols, determine the correct claims when run in
     isolation.
-    Returns a list of tuples (protocol,claimid)
+    Returns a tuple, consisting of
+    - a list of compiling protocols
+    - a list of tuples (protocol,claimid) wich denote correct claims
     """
-    correct = []
+    correctclaims = []
+    goodprotocols = []
     for protocol in protocolset:
         # verify protocol in isolation
         s = MyScyther([protocol])
         # investigate the results
-        for claim in s.claims:
-            if claim.okay:
-                correct.append((protocol,claim.id))
-    return correct
+        if not s.errors:
+            goodprotocols.append(protocol)
+            for claim in s.claims:
+                if claim.okay:
+                    correctclaims.append((protocol,claim.id))
+    return (goodprotocols,correctclaims)
 
 def findMPA(protocolset,protocol,claimid,maxcount=3):
     """
     The protocol claim is assumed to be correct. When does it break?
     """
     count = 2
+    if len(protocolset) < maxcount:
+        maxcount = len(protocolset)
 
     def verifyMPAlist(mpalist):
         # This should be a more restricted verification
-        print "verifying %s" % mpalist
-        s = MyScyther(mpalist)
+        s = MyScyther(mpalist,claimid)
         cl = s.getClaim(claimid)
         if cl:
             if not cl.okay:
                 # This is an MPA attack!
-                print "Attack!"
+                print "I've found a multi-protocol attack on claim %s in the context %s." % (claimid,str(mpalist))
                 return mpalist
-        return None
 
-    def constructMPAlist(mpalist,callback):
+    def constructMPAlist(mpalist,start,callback):
         if len(mpalist) < count:
-            for p in protocolset:
+            for pn in range(start,len(protocolset)):
+                p = protocolset[pn]
                 if p not in mpalist:
-                    return constructMPAlist(mpalist + [p],callback)
+                    constructMPAlist(mpalist + [p],pn+1,callback)
         else:
-            return callback(mpalist)
+            callback(mpalist)
 
     while count <= maxcount:
-        mpalist = constructMPAlist([protocol],verifyMPAlist)
-        if mpalist:
-            return mpalist
+        constructMPAlist([protocol],0,verifyMPAlist)
         count += 1
     return None
 
@@ -69,7 +80,7 @@ def findAllMPA(protocolset,maxcount=3):
     """
     Given a set of protocols, find multi-protocol attacks
     """
-    correct = getCorrectIsolatedClaims(protocolset)
+    (protocolset,correct) = getCorrectIsolatedClaims(protocolset)
     print correct
     for (protocol,claimid) in correct:
         mpalist = findMPA(protocolset,protocol,claimid,maxcount=3)