diff -r c7c34916027a -r 177826044cd9 wp/wp-includes/sodium_compat/src/Core/Util.php
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/wp/wp-includes/sodium_compat/src/Core/Util.php	Mon Oct 14 18:28:13 2019 +0200
@@ -0,0 +1,921 @@
+<?php
+
+if (class_exists('ParagonIE_Sodium_Core_Util', false)) {
+    return;
+}
+
+/**
+ * Class ParagonIE_Sodium_Core_Util
+ */
+abstract class ParagonIE_Sodium_Core_Util
+{
+    /**
+     * @param int $integer
+     * @param int $size (16, 32, 64)
+     * @return int
+     */
+    public static function abs($integer, $size = 0)
+    {
+        /** @var int $realSize */
+        $realSize = (PHP_INT_SIZE << 3) - 1;
+        if ($size) {
+            --$size;
+        } else {
+            /** @var int $size */
+            $size = $realSize;
+        }
+
+        $negative = -(($integer >> $size) & 1);
+        return (int) (
+            ($integer ^ $negative)
+                +
+            (($negative >> $realSize) & 1)
+        );
+    }
+
+    /**
+     * Convert a binary string into a hexadecimal string without cache-timing
+     * leaks
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $binaryString (raw binary)
+     * @return string
+     * @throws TypeError
+     */
+    public static function bin2hex($binaryString)
+    {
+        /* Type checks: */
+        if (!is_string($binaryString)) {
+            throw new TypeError('Argument 1 must be a string, ' . gettype($binaryString) . ' given.');
+        }
+
+        $hex = '';
+        $len = self::strlen($binaryString);
+        for ($i = 0; $i < $len; ++$i) {
+            /** @var array<int, int> $chunk */
+            $chunk = unpack('C', $binaryString[$i]);
+            /** @var int $c */
+            $c = $chunk[1] & 0xf;
+            /** @var int $b */
+            $b = $chunk[1] >> 4;
+            $hex .= pack(
+                'CC',
+                (87 + $b + ((($b - 10) >> 8) & ~38)),
+                (87 + $c + ((($c - 10) >> 8) & ~38))
+            );
+        }
+        return $hex;
+    }
+
+    /**
+     * Convert a binary string into a hexadecimal string without cache-timing
+     * leaks, returning uppercase letters (as per RFC 4648)
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $bin_string (raw binary)
+     * @return string
+     * @throws TypeError
+     */
+    public static function bin2hexUpper($bin_string)
+    {
+        $hex = '';
+        $len = self::strlen($bin_string);
+        for ($i = 0; $i < $len; ++$i) {
+            /** @var array<int, int> $chunk */
+            $chunk = unpack('C', $bin_string[$i]);
+            /**
+             * Lower 16 bits
+             *
+             * @var int $c
+             */
+            $c = $chunk[1] & 0xf;
+
+            /**
+             * Upper 16 bits
+             * @var int $b
+             */
+            $b = $chunk[1] >> 4;
+
+            /**
+             * Use pack() and binary operators to turn the two integers
+             * into hexadecimal characters. We don't use chr() here, because
+             * it uses a lookup table internally and we want to avoid
+             * cache-timing side-channels.
+             */
+            $hex .= pack(
+                'CC',
+                (55 + $b + ((($b - 10) >> 8) & ~6)),
+                (55 + $c + ((($c - 10) >> 8) & ~6))
+            );
+        }
+        return $hex;
+    }
+
+    /**
+     * Cache-timing-safe variant of ord()
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $chr
+     * @return int
+     * @throws SodiumException
+     * @throws TypeError
+     */
+    public static function chrToInt($chr)
+    {
+        /* Type checks: */
+        if (!is_string($chr)) {
+            throw new TypeError('Argument 1 must be a string, ' . gettype($chr) . ' given.');
+        }
+        if (self::strlen($chr) !== 1) {
+            throw new SodiumException('chrToInt() expects a string that is exactly 1 character long');
+        }
+        /** @var array<int, int> $chunk */
+        $chunk = unpack('C', $chr);
+        return (int) ($chunk[1]);
+    }
+
+    /**
+     * Compares two strings.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $left
+     * @param string $right
+     * @param int $len
+     * @return int
+     * @throws SodiumException
+     * @throws TypeError
+     */
+    public static function compare($left, $right, $len = null)
+    {
+        $leftLen = self::strlen($left);
+        $rightLen = self::strlen($right);
+        if ($len === null) {
+            $len = max($leftLen, $rightLen);
+            $left = str_pad($left, $len, "\x00", STR_PAD_RIGHT);
+            $right = str_pad($right, $len, "\x00", STR_PAD_RIGHT);
+        }
+
+        $gt = 0;
+        $eq = 1;
+        $i = $len;
+        while ($i !== 0) {
+            --$i;
+            $gt |= ((self::chrToInt($right[$i]) - self::chrToInt($left[$i])) >> 8) & $eq;
+            $eq &= ((self::chrToInt($right[$i]) ^ self::chrToInt($left[$i])) - 1) >> 8;
+        }
+        return ($gt + $gt + $eq) - 1;
+    }
+
+    /**
+     * If a variable does not match a given type, throw a TypeError.
+     *
+     * @param mixed $mixedVar
+     * @param string $type
+     * @param int $argumentIndex
+     * @throws TypeError
+     * @throws SodiumException
+     * @return void
+     */
+    public static function declareScalarType(&$mixedVar = null, $type = 'void', $argumentIndex = 0)
+    {
+        if (func_num_args() === 0) {
+            /* Tautology, by default */
+            return;
+        }
+        if (func_num_args() === 1) {
+            throw new TypeError('Declared void, but passed a variable');
+        }
+        $realType = strtolower(gettype($mixedVar));
+        $type = strtolower($type);
+        switch ($type) {
+            case 'null':
+                if ($mixedVar !== null) {
+                    throw new TypeError('Argument ' . $argumentIndex . ' must be null, ' . $realType . ' given.');
+                }
+                break;
+            case 'integer':
+            case 'int':
+                $allow = array('int', 'integer');
+                if (!in_array($type, $allow)) {
+                    throw new TypeError('Argument ' . $argumentIndex . ' must be an integer, ' . $realType . ' given.');
+                }
+                $mixedVar = (int) $mixedVar;
+                break;
+            case 'boolean':
+            case 'bool':
+                $allow = array('bool', 'boolean');
+                if (!in_array($type, $allow)) {
+                    throw new TypeError('Argument ' . $argumentIndex . ' must be a boolean, ' . $realType . ' given.');
+                }
+                $mixedVar = (bool) $mixedVar;
+                break;
+            case 'string':
+                if (!is_string($mixedVar)) {
+                    throw new TypeError('Argument ' . $argumentIndex . ' must be a string, ' . $realType . ' given.');
+                }
+                $mixedVar = (string) $mixedVar;
+                break;
+            case 'decimal':
+            case 'double':
+            case 'float':
+                $allow = array('decimal', 'double', 'float');
+                if (!in_array($type, $allow)) {
+                    throw new TypeError('Argument ' . $argumentIndex . ' must be a float, ' . $realType . ' given.');
+                }
+                $mixedVar = (float) $mixedVar;
+                break;
+            case 'object':
+                if (!is_object($mixedVar)) {
+                    throw new TypeError('Argument ' . $argumentIndex . ' must be an object, ' . $realType . ' given.');
+                }
+                break;
+            case 'array':
+                if (!is_array($mixedVar)) {
+                    if (is_object($mixedVar)) {
+                        if ($mixedVar instanceof ArrayAccess) {
+                            return;
+                        }
+                    }
+                    throw new TypeError('Argument ' . $argumentIndex . ' must be an array, ' . $realType . ' given.');
+                }
+                break;
+            default:
+                throw new SodiumException('Unknown type (' . $realType .') does not match expect type (' . $type . ')');
+        }
+    }
+
+    /**
+     * Evaluate whether or not two strings are equal (in constant-time)
+     *
+     * @param string $left
+     * @param string $right
+     * @return bool
+     * @throws SodiumException
+     * @throws TypeError
+     */
+    public static function hashEquals($left, $right)
+    {
+        /* Type checks: */
+        if (!is_string($left)) {
+            throw new TypeError('Argument 1 must be a string, ' . gettype($left) . ' given.');
+        }
+        if (!is_string($right)) {
+            throw new TypeError('Argument 2 must be a string, ' . gettype($right) . ' given.');
+        }
+
+        if (is_callable('hash_equals')) {
+            return hash_equals($left, $right);
+        }
+        $d = 0;
+        /** @var int $len */
+        $len = self::strlen($left);
+        if ($len !== self::strlen($right)) {
+            return false;
+        }
+        for ($i = 0; $i < $len; ++$i) {
+            $d |= self::chrToInt($left[$i]) ^ self::chrToInt($right[$i]);
+        }
+
+        if ($d !== 0) {
+            return false;
+        }
+        return $left === $right;
+    }
+
+    /**
+     * Convert a hexadecimal string into a binary string without cache-timing
+     * leaks
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $hexString
+     * @param bool $strictPadding
+     * @return string (raw binary)
+     * @throws RangeException
+     * @throws TypeError
+     */
+    public static function hex2bin($hexString, $strictPadding = false)
+    {
+        /* Type checks: */
+        if (!is_string($hexString)) {
+            throw new TypeError('Argument 1 must be a string, ' . gettype($hexString) . ' given.');
+        }
+
+        /** @var int $hex_pos */
+        $hex_pos = 0;
+        /** @var string $bin */
+        $bin = '';
+        /** @var int $c_acc */
+        $c_acc = 0;
+        /** @var int $hex_len */
+        $hex_len = self::strlen($hexString);
+        /** @var int $state */
+        $state = 0;
+        if (($hex_len & 1) !== 0) {
+            if ($strictPadding) {
+                throw new RangeException(
+                    'Expected an even number of hexadecimal characters'
+                );
+            } else {
+                $hexString = '0' . $hexString;
+                ++$hex_len;
+            }
+        }
+
+        $chunk = unpack('C*', $hexString);
+        while ($hex_pos < $hex_len) {
+            ++$hex_pos;
+            /** @var int $c */
+            $c = $chunk[$hex_pos];
+            /** @var int $c_num */
+            $c_num = $c ^ 48;
+            /** @var int $c_num0 */
+            $c_num0 = ($c_num - 10) >> 8;
+            /** @var int $c_alpha */
+            $c_alpha = ($c & ~32) - 55;
+            /** @var int $c_alpha0 */
+            $c_alpha0 = (($c_alpha - 10) ^ ($c_alpha - 16)) >> 8;
+            if (($c_num0 | $c_alpha0) === 0) {
+                throw new RangeException(
+                    'hex2bin() only expects hexadecimal characters'
+                );
+            }
+            /** @var int $c_val */
+            $c_val = ($c_num0 & $c_num) | ($c_alpha & $c_alpha0);
+            if ($state === 0) {
+                $c_acc = $c_val * 16;
+            } else {
+                $bin .= pack('C', $c_acc | $c_val);
+            }
+            $state ^= 1;
+        }
+        return $bin;
+    }
+
+    /**
+     * Turn an array of integers into a string
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param array<int, int> $ints
+     * @return string
+     */
+    public static function intArrayToString(array $ints)
+    {
+        /** @var array<int, int> $args */
+        $args = $ints;
+        foreach ($args as $i => $v) {
+            $args[$i] = (int) ($v & 0xff);
+        }
+        array_unshift($args, str_repeat('C', count($ints)));
+        return (string) (call_user_func_array('pack', $args));
+    }
+
+    /**
+     * Cache-timing-safe variant of ord()
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param int $int
+     * @return string
+     * @throws TypeError
+     */
+    public static function intToChr($int)
+    {
+        return pack('C', $int);
+    }
+
+    /**
+     * Load a 3 character substring into an integer
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $string
+     * @return int
+     * @throws RangeException
+     * @throws TypeError
+     */
+    public static function load_3($string)
+    {
+        /* Type checks: */
+        if (!is_string($string)) {
+            throw new TypeError('Argument 1 must be a string, ' . gettype($string) . ' given.');
+        }
+
+        /* Input validation: */
+        if (self::strlen($string) < 3) {
+            throw new RangeException(
+                'String must be 3 bytes or more; ' . self::strlen($string) . ' given.'
+            );
+        }
+        /** @var array<int, int> $unpacked */
+        $unpacked = unpack('V', $string . "\0");
+        return (int) ($unpacked[1] & 0xffffff);
+    }
+
+    /**
+     * Load a 4 character substring into an integer
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $string
+     * @return int
+     * @throws RangeException
+     * @throws TypeError
+     */
+    public static function load_4($string)
+    {
+        /* Type checks: */
+        if (!is_string($string)) {
+            throw new TypeError('Argument 1 must be a string, ' . gettype($string) . ' given.');
+        }
+
+        /* Input validation: */
+        if (self::strlen($string) < 4) {
+            throw new RangeException(
+                'String must be 4 bytes or more; ' . self::strlen($string) . ' given.'
+            );
+        }
+        /** @var array<int, int> $unpacked */
+        $unpacked = unpack('V', $string);
+        return (int) ($unpacked[1] & 0xffffffff);
+    }
+
+    /**
+     * Load a 8 character substring into an integer
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $string
+     * @return int
+     * @throws RangeException
+     * @throws SodiumException
+     * @throws TypeError
+     */
+    public static function load64_le($string)
+    {
+        /* Type checks: */
+        if (!is_string($string)) {
+            throw new TypeError('Argument 1 must be a string, ' . gettype($string) . ' given.');
+        }
+
+        /* Input validation: */
+        if (self::strlen($string) < 4) {
+            throw new RangeException(
+                'String must be 4 bytes or more; ' . self::strlen($string) . ' given.'
+            );
+        }
+        if (PHP_VERSION_ID >= 50603 && PHP_INT_SIZE === 8) {
+            /** @var array<int, int> $unpacked */
+            $unpacked = unpack('P', $string);
+            return (int) $unpacked[1];
+        }
+
+        /** @var int $result */
+        $result  = (self::chrToInt($string[0]) & 0xff);
+        $result |= (self::chrToInt($string[1]) & 0xff) <<  8;
+        $result |= (self::chrToInt($string[2]) & 0xff) << 16;
+        $result |= (self::chrToInt($string[3]) & 0xff) << 24;
+        $result |= (self::chrToInt($string[4]) & 0xff) << 32;
+        $result |= (self::chrToInt($string[5]) & 0xff) << 40;
+        $result |= (self::chrToInt($string[6]) & 0xff) << 48;
+        $result |= (self::chrToInt($string[7]) & 0xff) << 56;
+        return (int) $result;
+    }
+
+    /**
+     * @internal You should not use this directly from another application
+     *
+     * @param string $left
+     * @param string $right
+     * @return int
+     * @throws SodiumException
+     * @throws TypeError
+     */
+    public static function memcmp($left, $right)
+    {
+        if (self::hashEquals($left, $right)) {
+            return 0;
+        }
+        return -1;
+    }
+
+    /**
+     * Multiply two integers in constant-time
+     *
+     * Micro-architecture timing side-channels caused by how your CPU
+     * implements multiplication are best prevented by never using the
+     * multiplication operators and ensuring that our code always takes
+     * the same number of operations to complete, regardless of the values
+     * of $a and $b.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param int $a
+     * @param int $b
+     * @param int $size Limits the number of operations (useful for small,
+     *                  constant operands)
+     * @return int
+     */
+    public static function mul($a, $b, $size = 0)
+    {
+        if (ParagonIE_Sodium_Compat::$fastMult) {
+            return (int) ($a * $b);
+        }
+
+        static $defaultSize = null;
+        /** @var int $defaultSize */
+        if (!$defaultSize) {
+            /** @var int $defaultSize */
+            $defaultSize = (PHP_INT_SIZE << 3) - 1;
+        }
+        if ($size < 1) {
+            /** @var int $size */
+            $size = $defaultSize;
+        }
+        /** @var int $size */
+
+        $c = 0;
+
+        /**
+         * Mask is either -1 or 0.
+         *
+         * -1 in binary looks like 0x1111 ... 1111
+         *  0 in binary looks like 0x0000 ... 0000
+         *
+         * @var int
+         */
+        $mask = -(($b >> ((int) $defaultSize)) & 1);
+
+        /**
+         * Ensure $b is a positive integer, without creating
+         * a branching side-channel
+         *
+         * @var int $b
+         */
+        $b = ($b & ~$mask) | ($mask & -$b);
+
+        /**
+         * Unless $size is provided:
+         *
+         * This loop always runs 32 times when PHP_INT_SIZE is 4.
+         * This loop always runs 64 times when PHP_INT_SIZE is 8.
+         */
+        for ($i = $size; $i >= 0; --$i) {
+            $c += (int) ($a & -($b & 1));
+            $a <<= 1;
+            $b >>= 1;
+        }
+
+        /**
+         * If $b was negative, we then apply the same value to $c here.
+         * It doesn't matter much if $a was negative; the $c += above would
+         * have produced a negative integer to begin with. But a negative $b
+         * makes $b >>= 1 never return 0, so we would end up with incorrect
+         * results.
+         *
+         * The end result is what we'd expect from integer multiplication.
+         */
+        return (int) (($c & ~$mask) | ($mask & -$c));
+    }
+
+    /**
+     * Convert any arbitrary numbers into two 32-bit integers that represent
+     * a 64-bit integer.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param int|float $num
+     * @return array<int, int>
+     */
+    public static function numericTo64BitInteger($num)
+    {
+        $high = 0;
+        /** @var int $low */
+        $low = $num & 0xffffffff;
+
+        if ((+(abs($num))) >= 1) {
+            if ($num > 0) {
+                /** @var int $high */
+                $high = min((+(floor($num/4294967296))), 4294967295);
+            } else {
+                /** @var int $high */
+                $high = ~~((+(ceil(($num - (+((~~($num)))))/4294967296))));
+            }
+        }
+        return array((int) $high, (int) $low);
+    }
+
+    /**
+     * Store a 24-bit integer into a string, treating it as big-endian.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param int $int
+     * @return string
+     * @throws TypeError
+     */
+    public static function store_3($int)
+    {
+        /* Type checks: */
+        if (!is_int($int)) {
+            if (is_numeric($int)) {
+                $int = (int) $int;
+            } else {
+                throw new TypeError('Argument 1 must be an integer, ' . gettype($int) . ' given.');
+            }
+        }
+        /** @var string $packed */
+        $packed = pack('N', $int);
+        return self::substr($packed, 1, 3);
+    }
+
+    /**
+     * Store a 32-bit integer into a string, treating it as little-endian.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param int $int
+     * @return string
+     * @throws TypeError
+     */
+    public static function store32_le($int)
+    {
+        /* Type checks: */
+        if (!is_int($int)) {
+            if (is_numeric($int)) {
+                $int = (int) $int;
+            } else {
+                throw new TypeError('Argument 1 must be an integer, ' . gettype($int) . ' given.');
+            }
+        }
+
+        /** @var string $packed */
+        $packed = pack('V', $int);
+        return $packed;
+    }
+
+    /**
+     * Store a 32-bit integer into a string, treating it as big-endian.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param int $int
+     * @return string
+     * @throws TypeError
+     */
+    public static function store_4($int)
+    {
+        /* Type checks: */
+        if (!is_int($int)) {
+            if (is_numeric($int)) {
+                $int = (int) $int;
+            } else {
+                throw new TypeError('Argument 1 must be an integer, ' . gettype($int) . ' given.');
+            }
+        }
+
+        /** @var string $packed */
+        $packed = pack('N', $int);
+        return $packed;
+    }
+
+    /**
+     * Stores a 64-bit integer as an string, treating it as little-endian.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param int $int
+     * @return string
+     * @throws TypeError
+     */
+    public static function store64_le($int)
+    {
+        /* Type checks: */
+        if (!is_int($int)) {
+            if (is_numeric($int)) {
+                $int = (int) $int;
+            } else {
+                throw new TypeError('Argument 1 must be an integer, ' . gettype($int) . ' given.');
+            }
+        }
+
+        if (PHP_INT_SIZE === 8) {
+            if (PHP_VERSION_ID >= 50603) {
+                /** @var string $packed */
+                $packed = pack('P', $int);
+                return $packed;
+            }
+            return self::intToChr($int & 0xff) .
+                self::intToChr(($int >>  8) & 0xff) .
+                self::intToChr(($int >> 16) & 0xff) .
+                self::intToChr(($int >> 24) & 0xff) .
+                self::intToChr(($int >> 32) & 0xff) .
+                self::intToChr(($int >> 40) & 0xff) .
+                self::intToChr(($int >> 48) & 0xff) .
+                self::intToChr(($int >> 56) & 0xff);
+        }
+        if ($int > PHP_INT_MAX) {
+            list($hiB, $int) = self::numericTo64BitInteger($int);
+        } else {
+            $hiB = 0;
+        }
+        return
+            self::intToChr(($int      ) & 0xff) .
+            self::intToChr(($int >>  8) & 0xff) .
+            self::intToChr(($int >> 16) & 0xff) .
+            self::intToChr(($int >> 24) & 0xff) .
+            self::intToChr($hiB & 0xff) .
+            self::intToChr(($hiB >>  8) & 0xff) .
+            self::intToChr(($hiB >> 16) & 0xff) .
+            self::intToChr(($hiB >> 24) & 0xff);
+    }
+
+    /**
+     * Safe string length
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @ref mbstring.func_overload
+     *
+     * @param string $str
+     * @return int
+     * @throws TypeError
+     */
+    public static function strlen($str)
+    {
+        /* Type checks: */
+        if (!is_string($str)) {
+            throw new TypeError('String expected');
+        }
+
+        return (int) (
+        self::isMbStringOverride()
+            ? mb_strlen($str, '8bit')
+            : strlen($str)
+        );
+    }
+
+    /**
+     * Turn a string into an array of integers
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $string
+     * @return array<int, int>
+     * @throws TypeError
+     */
+    public static function stringToIntArray($string)
+    {
+        if (!is_string($string)) {
+            throw new TypeError('String expected');
+        }
+        /**
+         * @var array<int, int>
+         */
+        $values = array_values(
+            unpack('C*', $string)
+        );
+        return $values;
+    }
+
+    /**
+     * Safe substring
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @ref mbstring.func_overload
+     *
+     * @param string $str
+     * @param int $start
+     * @param int $length
+     * @return string
+     * @throws TypeError
+     */
+    public static function substr($str, $start = 0, $length = null)
+    {
+        /* Type checks: */
+        if (!is_string($str)) {
+            throw new TypeError('String expected');
+        }
+
+        if ($length === 0) {
+            return '';
+        }
+
+        if (self::isMbStringOverride()) {
+            if (PHP_VERSION_ID < 50400 && $length === null) {
+                $length = self::strlen($str);
+            }
+            $sub = (string) mb_substr($str, $start, $length, '8bit');
+        } elseif ($length === null) {
+            $sub = (string) substr($str, $start);
+        } else {
+            $sub = (string) substr($str, $start, $length);
+        }
+        if ($sub !== '') {
+            return $sub;
+        }
+        return '';
+    }
+
+    /**
+     * Compare a 16-character byte string in constant time.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $a
+     * @param string $b
+     * @return bool
+     * @throws SodiumException
+     * @throws TypeError
+     */
+    public static function verify_16($a, $b)
+    {
+        /* Type checks: */
+        if (!is_string($a)) {
+            throw new TypeError('String expected');
+        }
+        if (!is_string($b)) {
+            throw new TypeError('String expected');
+        }
+        return self::hashEquals(
+            self::substr($a, 0, 16),
+            self::substr($b, 0, 16)
+        );
+    }
+
+    /**
+     * Compare a 32-character byte string in constant time.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $a
+     * @param string $b
+     * @return bool
+     * @throws SodiumException
+     * @throws TypeError
+     */
+    public static function verify_32($a, $b)
+    {
+        /* Type checks: */
+        if (!is_string($a)) {
+            throw new TypeError('String expected');
+        }
+        if (!is_string($b)) {
+            throw new TypeError('String expected');
+        }
+        return self::hashEquals(
+            self::substr($a, 0, 32),
+            self::substr($b, 0, 32)
+        );
+    }
+
+    /**
+     * Calculate $a ^ $b for two strings.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @param string $a
+     * @param string $b
+     * @return string
+     * @throws TypeError
+     */
+    public static function xorStrings($a, $b)
+    {
+        /* Type checks: */
+        if (!is_string($a)) {
+            throw new TypeError('Argument 1 must be a string');
+        }
+        if (!is_string($b)) {
+            throw new TypeError('Argument 2 must be a string');
+        }
+
+        return (string) ($a ^ $b);
+    }
+
+    /**
+     * Returns whether or not mbstring.func_overload is in effect.
+     *
+     * @internal You should not use this directly from another application
+     *
+     * @return bool
+     */
+    protected static function isMbStringOverride()
+    {
+        static $mbstring = null;
+
+        if ($mbstring === null) {
+            $mbstring = extension_loaded('mbstring')
+                &&
+            ((int) (ini_get('mbstring.func_overload')) & MB_OVERLOAD_STRING);
+        }
+        /** @var bool $mbstring */
+
+        return $mbstring;
+    }
+}