anchor.diff:  
   (* ------------------------------------------------------------------------------- *)
   let remove self sid role hint =
  -    let key = bytes_of_key (sid,role,hint) in
  +    let key = bytes_of_key (Bytes.cbytes sid, role, hint) in
       let db  = DB.opendb self.filename in
   
       try
  
positive.code: (* ------------------------------------------------------------------------------- *)
  type StorableSession = SessionInfo * PRF.masterSecret
  type SessionIndex = sessionID * Role * Cert.hint
  #if ideal
  type entry = sessionID * Role * Cert.hint * StorableSession
  type t = entry list  
  
negative.code:         | Some x -> None
  
  (* ------------------------------------------------------------------------------- *)
  let bytes_of_key (k : byte[] * Role * string) =
      let bf = new BinaryFormatter () in
      let m  = new MemoryStream () in
          bf.Serialize(m, k); m.ToArray ()
  