Skeletal systems exploit algorithmical skeletons technology to provide the user very high level, efficient parallel programming environments. They have been recently demonstrated to be suitable for highly distributed architectures, such as workstation clusters, networks and grids. However, when using skeletal system for grid programming care must be taken to secure data and code transfers across nondedicated, non-secure network links. In this work we take into account the cost of security introduction in muskel, a Java based skeletal system exploiting macro data flow implementation technology. We consider the adoption of mechanisms that allow securing all the communications taking place between remote, unreliable nodes and we evaluate the cost of such mechanisms. In particular, we consider the implications on the computational grains needed to scale secure and insecure skeletal computations.