title: RSA and exponent not relatively prime with Euler Phi
body: <p>I would like to know which drawbacks are there if the public exponent (e) is not coprime with the Euler phi (phi(N)) in RSA. That is to say GCD(e, phi(n)) != 1.</p>
  
  <p>As far as I know the drawback is that in this way we are not sure that there exists a d such that e*d = 1 mod phi. Are there any other drawbacks?</p>