It's not really a temporal relationship

wiki/src/install/inc/steps/download.inline.html

@@ -457,7 +457,7 @@ attack.</p>
 
 <p>OpenPGP verification is the only technique that protects you if
 our website is compromised or if you are a victim of a man-in-the-middle
-attack. But, you first need to authenticate the Tails signing key
+attack. But, for that you need to authenticate the Tails signing key
 through the OpenPGP Web of Trust.</p>
 
 <div class="note">