Risks of backdoors in software are evident ever since Ken Thompson's Turing Award Lecture "Reflections on Trusting Trust". Certainly this applies to hardware just as well.
Limiting ourselves here to software, what are the genuinely good solutions of protection against backdoors? Owing to certain recent reports in the media on global Internet surveillance by nation-states, the fear of potential backdoors in software that are destined to secure the IT-securitry once again surfaces, e.g. in http://www.golem.de/news/prism-skandal-furcht-vor-hintertueren-in-us-software-und-hardware-1306-100012.html (in German).
Long ago I learned that for standard conformity of programming language compilers there are test centres of the diverse national standard bodies that verify the software and issue certificates to those compiler producers that apply for certification. Could an analogous procedure eventually be a practically realizable solution or at least a good compromise?