diff --git a/phpseclib/Crypt/RSA/PrivateKey.php b/phpseclib/Crypt/RSA/PrivateKey.php
index 4a3c288d..52abfb82 100644
--- a/phpseclib/Crypt/RSA/PrivateKey.php
+++ b/phpseclib/Crypt/RSA/PrivateKey.php
@@ -228,7 +228,7 @@ class PrivateKey extends RSA implements Common\PrivateKey
         $h = $this->hash->hash($m2);
         $ps = str_repeat(chr(0), $emLen - $sLen - $this->hLen - 2);
         $db = $ps . chr(1) . $salt;
-        $dbMask = $this->mgf1($h, $emLen - $this->hLen - 1);
+        $dbMask = $this->mgf1($h, $emLen - $this->hLen - 1); // ie. stlren($db)
         $maskedDB = $db ^ $dbMask;
         $maskedDB[0] = ~chr(0xFF << ($emBits & 7)) & $maskedDB[0];
         $em = $maskedDB . $h . chr(0xBC);