diff --git a/phpseclib/Crypt/Blowfish.php b/phpseclib/Crypt/Blowfish.php
index cc885114..6b7ff76e 100644
--- a/phpseclib/Crypt/Blowfish.php
+++ b/phpseclib/Crypt/Blowfish.php
@@ -479,18 +479,83 @@ class Crypt_Blowfish extends Crypt_Base
         $l = $in[1];
         $r = $in[2];
 
-        for ($i = 0; $i < 16; $i+= 2) {
-            $l^= $p[$i];
-            $r^= $this->safe_intval(($this->safe_intval($sb_0[$l >> 24 & 0xff]  + $sb_1[$l >> 16 & 0xff]) ^
-                  $sb_2[$l >>  8 & 0xff]) +
-                  $sb_3[$l       & 0xff]);
+        list($r, $l) = CRYPT_BASE_USE_SAFE_INTVAL ?
+            $this->_encryptBlockHelperFast($l, $r, $sb_0, $sb_1, $sb_2, $sb_3, $p) :
+            $this->_encryptBlockHelperSlow($l, $r, $sb_0, $sb_1, $sb_2, $sb_3, $p);
 
-            $r^= $p[$i + 1];
-            $l^= $this->safe_intval(($this->safe_intval($sb_0[$r >> 24 & 0xff]  + $sb_1[$r >> 16 & 0xff]) ^
-                  $sb_2[$r >>  8 & 0xff]) +
-                  $sb_3[$r       & 0xff]);
-        }
-        return pack("N*", $r ^ $p[17], $l ^ $p[16]);
+        return pack("N*", $r, $l);
+    }
+
+    /**
+     * Fast helper function for block encryption
+     *
+     * @access private
+     * @param int $x0
+     * @param int $x1
+     * @param int[] $sbox0
+     * @param int[] $sbox1
+     * @param int[] $sbox2
+     * @param int[] $sbox3
+     * @param int[] $p
+     * @return int[]
+     */
+    function _encryptBlockHelperFast($x0, $x1, $sbox0, $sbox1, $sbox2, $sbox3, $p)
+    {
+        $x0 ^= $p[0];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[1];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[2];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[3];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[4];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[5];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[6];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[7];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[8];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[9];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[10];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[11];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[12];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[13];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[14];
+        $x1 ^= ((($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[15];
+        $x0 ^= ((($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[16];
+
+        return [$x1 & 0xFFFFFFFF ^ $p[17], $x0 & 0xFFFFFFFF];
+    }
+
+    /**
+     * Slow helper function for block encryption
+     *
+     * @access private
+     * @param int $x0
+     * @param int $x1
+     * @param int[] $sbox0
+     * @param int[] $sbox1
+     * @param int[] $sbox2
+     * @param int[] $sbox3
+     * @param int[] $p
+     * @return int[]
+     */
+    function _encryptBlockHelperSlow($x0, $x1, $sbox0, $sbox1, $sbox2, $sbox3, $p)
+    {
+        $x0^= $p[0];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[1];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[2];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[3];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[4];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[5];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[6];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[7];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[8];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[9];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[10];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[11];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[12];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[13];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[14];
+        $x1^= $this->safe_intval(($this->safe_intval($sbox0[($x0 & 0xFF000000) >> 24] + $sbox1[($x0 & 0xFF0000) >> 16]) ^ $sbox2[($x0 & 0xFF00) >> 8]) + $sbox3[$x0 & 0xFF]) ^ $p[15];
+        $x0^= $this->safe_intval(($this->safe_intval($sbox0[($x1 & 0xFF000000) >> 24] + $sbox1[($x1 & 0xFF0000) >> 16]) ^ $sbox2[($x1 & 0xFF00) >> 8]) + $sbox3[$x1 & 0xFF]) ^ $p[16];
+
+        return [$x1 & 0xFFFFFFFF ^ $p[17], $x0 & 0xFFFFFFFF];
     }
 
     /**