Check expectedProofPurpose before checking signature.

index.html

@@ -1735,6 +1735,11 @@ <h3>Verify Proof</h3>
 MUST be raised.
           </li>
           <li>
+If the <var>proof</var>.<var>proofPurpose</var> value does not match
+<var>options</var>.<var>expectedProofPurpose</var>, a
+`MISMATCHED_PROOF_PURPOSE_ERROR` MUST be raised.
+          </li>
+          <li>
 Let <var>unsecuredDocument</var> be a copy of <var>securedDocument</var> with
 the `proof` value removed.
           </li>
@@ -1762,11 +1767,6 @@ <h3>Verify Proof</h3>
 parameters provided as inputs to the algorithm.
           </li>
           <li>
-If the <var>proof</var>.<var>proofPurpose</var> value does not match
-<var>options</var>.<var>proofPurpose</var>, a `MISMATCHED_PROOF_PURPOSE_ERROR`
-MUST be raised.
-          </li>
-          <li>
 If the <var>proof</var>.<var>created</var> is set and it deviates more than
 <var>options</var>.<var>acceptableCreatedTimeDeviationInSeconds</var> seconds, a
 `CREATED_TIME_DEVIATION_ERROR` MUST be raised.