Open design would seem to favor the attacker, because it certainly opens the implementation and perhaps also the design for the attacker to study. Justify that open design overrides this seeming advantage and actually leads to solid security.

Explanation:

Open  design  allows  for  much  closer  inspection  of  the  security  system—more  awareness  of  the  security  practices  in  place  is  more  likely  to  reveal  vulnerabilities  to  enable  resolving  those  vulnerabilities  rather  than  their  exploitation.  Obscurity  is  an  insufficient  security  mechanism,  open  design  allows  a  more  thorough  inspection,  and  knowing  that  a  design  will  be  open  should  make  designers  more  careful