diff --git a/phpseclib/Common/Functions/Strings.php b/phpseclib/Common/Functions/Strings.php
index 6a024c36..e6483e91 100644
--- a/phpseclib/Common/Functions/Strings.php
+++ b/phpseclib/Common/Functions/Strings.php
@@ -308,7 +308,7 @@ abstract class Strings
      * @param string $x
      * @return string
      */
-    public static function bin2bits($x)
+    public static function bin2bits($x, $trim = true)
     {
         /*
         // the pure-PHP approach is slower than the GMP approach BUT
@@ -337,7 +337,7 @@ abstract class Strings
             }
         }
 
-        return ltrim($bits, '0');
+        return $trim ? ltrim($bits, '0') : $bits;
     }
 
     /**
@@ -350,14 +350,21 @@ abstract class Strings
     public static function switchEndianness($x)
     {
         $r = '';
-        // from http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith32Bits
         for ($i = strlen($x) - 1; $i >= 0; $i--) {
             $b = ord($x[$i]);
-            $p1 = ($b * 0x0802) & 0x22110;
-            $p2 = ($b * 0x8020) & 0x88440;
-            $r.= chr(
-                (($p1 | $p2) * 0x10101) >> 16
-            );
+            if (PHP_INT_SIZE === 8) {
+                // 3 operations
+                // from http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith64BitsDiv
+                $r.= chr((($b * 0x0202020202) & 0x010884422010) % 1023);
+            } else {
+                // 7 operations
+                // from http://graphics.stanford.edu/~seander/bithacks.html#ReverseByteWith32Bits
+                $p1 = ($b * 0x0802) & 0x22110;
+                $p2 = ($b * 0x8020) & 0x88440;
+                $r.= chr(
+                    (($p1 | $p2) * 0x10101) >> 16
+                );
+            }
         }
         return $r;
     }