title: Developing a kernel patch or driver for windows?
body: <p>How long, approximately, would it take to develop a kernel patch or driver for the windows NT kernel/series of kernels, that would introduce new functionality, or replace existing functionality? </p>
  
  <p>For example, to add in a different encryption algorithm, or to implement some sort of new security model.</p>
  
  <p>What are the advantages/disadvantages between actually writing a kernel patch, and a driver?</p>
  
  <p>Can a driver be theoretically bypassed, in a way a kernel patch cannot?</p>
  
  <p>I understand the windows kernel is proprietary and it is hard to write a kernel patch for it, but this is exactly what several companies, notably AV companies do, without cooperation from Microsoft, so it is possible...</p>