Maybe Poor Johnny Really Cannot Encrypt – The Case for a Complexity Theory for Usable Security

Psychology and neuroscience literature shows the existance of upper bounds on the human capacity for executing cognitive tasks and for information processing. These bounds are where, demonstrably, people start experiencing cognitive strain and consequently committing errors in the tasks execution. We argue that the usable security discipline should scientifically understand such bounds in order to have realistic expectations about what people can or cannot attain when coping with security tasks. This may shed light on whether Johnny will be ever be able to encrypt. We propose a conceptual framework for evaluation of human capacities in security that also assigns systems to complexity categories according to their security and usability. From what we have initiated in this paper, we ultimately aim at providing designers of security mechanisms and policies with the ability to say: "This feature of the security mechanism X or this security policy element Y is inappropriate, because this evidence shows that it is beyond the capacity of its target community".