--+++ Crititcal Bugs

   * soph segfaults at no switch or -r4 (-r3 is okay??) using non-debug version.
   * './scyther -a ../spdl/nsl3.spdl --increment-runs' segfaults. The main reason is that the Archne engine uses runs in a different way.
     Maybe it is best to disable --increment rules for non-ModelChecker verification.

---+++ Bugs

   * Problem with goal bindings: instantiation of variable with a tuple might
  introduce a tuple goal, which is forbidden. We must find a way to deal with this. This typically occurs in type flaw searches.
   * Arachne seems to trip over claims with empty prec sets. Maybe we
  simply should not test these.
   * Splice/AS does not work well because priority key search stumbles over the
  public key search stuff. That is a flaw in the heuristic: we should not look
  for anything that is in the intruder knowledge already. In fact, it is a
  problem with branching. We should not look for PK(X), even if X is a
  variable. Priority should go to keys of which the constructor is not in M_0,
  maybe that heuristic works.
  However, there seems to be an infinite loop for this in the algorithm, which
  I did not anticipate. Investigate!
  <br>
  Maybe self-loops are the problem. This has to do with tuple alternation
  decoding. Consider re-introducing explicit intruder strands OR self-loop
  pruning.

---+++ Would like to have

---++++ ArachneEngine

   * There is no good test on the correct workings of
     add_goals/destruction of these. We can test this if after
     termination, we have 0 goals; for this we need to store the
     initially added goals as well. Furthermore, we can generate an
     error when <0 goals occur.
   * Consider where in Arachne dependency graph is used. If this is only for
     pruning states, we can construct it there only. However, the base 'role
     defs/bindings' graph might be re-used.
   * Add switch for arachne to prune encryption levels when using -m2.
   * To store attacks for arachne, maybe the following is needed:
      * The roles for each run
      * The variable bindings for all (local) variables
      * The goal bindings
   * Agent terms must have keylevel 0; enforce this!
   * Select_goal should consider, for singular variables, whether their
     type can be found in M_0. If so, the goal can be ignored.
   * Fix 'never sent secrets' list, that are e.g. secret keys of regular agents
     and such. The intruder can never learn these, we need this for pruning.
     If a goal is such a term, we prune. Investigate how this can be incorporated.
     Investigate also whether this actually makes a difference.
   * Make 'generate_trace_bindings' to create the bindings for a given trace.
     Note that there can be multiple solutions; for now, simply try to take the
     shortest one.

---++++ ModelChecker

   * For secrecy, one trusted agent and one untrusted agent suffices.
     Implement this in the modelchecker.
   * Implement delayed protocol compiler (on run demand only) for the modelchecker?

---++++ Misc

   * Make different error codes for compilation error/ other error. This can be
     useful for scripts. However, it might shift some constants for the Elegast
     scripts.
   * Rewrite termMguTerm such that it iterates and adapt all functions
     using it. This is to allow for associative tupling later.
   * Fix constants in intruder knowledge. Auto add single one of each type,
     when typed expl. Add single constant when untyped. Fix this also in
     semantics, and add proof to establish sufficiency.
   * Fix function handling (signatures).
   * Move initial intruder knowledge maybe into the title of the MSC.
   * Implement run knowledge, and use this in protocol compiler.
   * Introduce 'Ticket' default type in the compiler, along with some
     handling for that.
   * The 'choose' operator must always be typed, I think. Yes.
   * The woolam-ce is incorrect because it is illegal to have a variable
     term in a key that is read, by CMV semantics. I don't know what it
     means for CE semantics (yet).
   * Idea: run bla.bla(params) [compromised <localterm> [,<localterm>] ];
      1. These local terms are given to the intruder. Technically this
         should only happen _after_ they are first sent in the run. Maybe add
         this to send semantics: if termOccurs(sendterm, compromisedterm) then
         add compromisedterm to M, remove compromisedterm from list of terms to
         compromise.
      1. All claims in the run are ignored (add untrusted flag to run)
         Alternative: run x.x(x) untrusted; or just compromised, to give up
         all constants.
         Note this is not sufficient yet, because it does not consider any
         partner runs. Maybe declare a 'compromised' section first; other runs
         will only activate after these have completed. Note this is much more
         expensive.
   * Woolam-ce gives nothing. But then again, it's a wrong impl.
   * Global/protocol variables should not exist in the current system.
   * run nsl.initiator(alice, all Agent) constructs?
      * 'all' would generate the roles with the corresponding type.
      * or maybe for clarity/complexity control: use 'runs' for constructs
        with 'all' in it.
   * Maybe function application ought to be a different basic term type.
   * After role construction, msc consistency can be checked.
   * Reduce knowledge to a simple term list? That would simplify a number
     of things, and also allow for easier addition of stuff.
   * How is % notation handled in Casper?
   * Vernam encryption?

---++++ ConstraintLogic (and thus obsolete)

   * CLP: variables in keys must be branched: maybe even in three situations
     (have key and contents, have inverse key and content, nothing)
   * How should claims behave (trusted/untrusted) wrt uninstantiated
     agents? Branch again? That's what is causing the nsl3-var problem.
   * Constraints might be a part of a knowledge thing, because with we
     might now have a number of local knowledge sets, each with their own
     constraint sets. That doesn't make it easier though :( and will cause
     some performance loss I suppose. Each local set has to remain
     solveable as well.
   * Issue: how do untrusted claims work in the context of an intruder?
     Claim must be checked if it can be solved such that at least one of
     the agents is trusted.