title: How do I prevent the "The package was signed with an invalid certificate" warning when installing my signed application in Mountain Lion?
body: <p>I have an application which I have signed using <code>[path]/PackageMaker --sign [MyPackage].pkg -c "3rd Party Mac Developer Installer: [MyCompany]" -o [MyPackage]-signed.pkg</code>.</p>
  
  <p>This succeeds and <code>spctl --assess --type install [MyPackage]-signed.pkg</code> also succeeds.</p>
  
  <p>But when I try to install it on a computer running OS X 10.8 Mountain Lion I get a warning:</p>
  
  <blockquote>
    <p>The package was signed with an invalid certificate. This package might not install what you expect. Do you want to continue with the installation anyway?</p>
  </blockquote>
  
  <p>If I show the certificate, the name is "3rd Party Mac Developer Installer: [MyCompany]" and it is listed as issued by "Apple Worldwide Developer Relations Certification Authority". A warning is displayed that "This certificate was signed by an unknown authority."</p>
  
  <p>The computer's security settings are set to "Allow applications downloaded from: Mac App Store and identified developers".</p>
  
  <p>I've tried both packagemaker (from Xcode 3.2.4) and PackageMaker (3.0.6 from the auxiliary tools download) with the same result.</p>
  
  <p>The certificate was requested from within Xcode 4 and appears to be correct from what I can tell. It shows up correctly in Keychain Access with a private key nested underneath it.</p>
  
  <p>What do I need to do to get my application's installer package to run without displaying this warning in Mountain Lion?</p>