diff --git a/phpseclib/Crypt/Random.php b/phpseclib/Crypt/Random.php
index 8f53eb31..e0961a72 100644
--- a/phpseclib/Crypt/Random.php
+++ b/phpseclib/Crypt/Random.php
@@ -151,7 +151,10 @@ class Random
                 (isset($_POST) ? phpseclib_safe_serialize($_POST) : '') .
                 (isset($_GET) ? phpseclib_safe_serialize($_GET) : '') .
                 (isset($_COOKIE) ? phpseclib_safe_serialize($_COOKIE) : '') .
-                phpseclib_safe_serialize($GLOBALS) .
+                // as of PHP 8.1 $GLOBALS cann't be accessed by reference, which eliminates
+                // the need for phpseclib_safe_serialize. see https://wiki.php.net/rfc/restrict_globals_usage
+                // for more info
+                (version_compare(PHP_VERSION, '8.1.0', '>=') ? serialize($GLOBALS) : phpseclib_safe_serialize($GLOBALS)) .
                 phpseclib_safe_serialize($_SESSION) .
                 phpseclib_safe_serialize($_OLD_SESSION)
             ));
diff --git a/phpseclib/Math/BigInteger.php b/phpseclib/Math/BigInteger.php
index 7c0b0a8d..8d1291db 100644
--- a/phpseclib/Math/BigInteger.php
+++ b/phpseclib/Math/BigInteger.php
@@ -372,7 +372,7 @@ class BigInteger
                         break;
                     case self::MODE_BCMATH:
                         // round $len to the nearest 4 (thanks, DavidMJ!)
-                        $len = (strlen($x) + 3) & 0xFFFFFFFC;
+                        $len = (strlen($x) + 3) & ~3;
 
                         $x = str_pad($x, $len, chr(0), STR_PAD_LEFT);
 
diff --git a/phpseclib/Net/SFTP.php b/phpseclib/Net/SFTP.php
index ade0ea5c..e0561c74 100644
--- a/phpseclib/Net/SFTP.php
+++ b/phpseclib/Net/SFTP.php
@@ -422,7 +422,7 @@ class SFTP extends SSH2
             // yields inconsistent behavior depending on how php is compiled.  so we left shift -1 (which, in
             // two's compliment, consists of all 1 bits) by 31.  on 64-bit systems this'll yield 0xFFFFFFFF80000000.
             // that's not a problem, however, and 'anded' and a 32-bit number, as all the leading 1 bits are ignored.
-            (-1 << 31) & 0xFFFFFFFF => 'NET_SFTP_ATTR_EXTENDED'
+            (PHP_INT_SIZE == 4 ? -1 : 0xFFFFFFFF) => 'NET_SFTP_ATTR_EXTENDED'
         );
         $this->open_flags = array(
             0x00000001 => 'NET_SFTP_OPEN_READ',