BigInteger::modPow() - Code Metrics - Inspection of "Useless statements removed" - Spomky-Labs/jose - Measure and Improve Code Quality continuously with Scrutinizer

Failed Conditions
Push — PHPSecLib_Rid ( 32d4bc...6a2b08 )

by Florent
created 2016-07-29 07:49 UTC
BigInteger::modPow() B

↳ Parent: BigInteger
Complexity

Conditions	5
Paths	12
Size

Total Lines	20
Code Lines	11
Duplication

Lines	0
Ratio	0 %
Importance

Changes	4
Bugs	1	Features	0
Metric	Value
c	4
b	1
f	0
dl	0
loc	20
rs	8.8571
cc	5
eloc	11
nc	12
nop	2
<?php

/*
 * The MIT License (MIT)
 *
 * Copyright (c) 2014-2016 Spomky-Labs
 *
 * This software may be modified and distributed under the terms
 * of the MIT license.  See the LICENSE file for details.
 */

namespace Jose\Util;

final class BigInteger
{
    /**
     * Holds the BigInteger's value.
     *
     * @var resource
     */
    private $value;

    /**
     * Holds the BigInteger's magnitude.
     *
     * @var bool
     */
    private $is_negative = false;

    /**
     * Precision.
     */
    private $precision = -1;

    /**
     * Precision Bitmask.
     */
    private $bitmask = false;

    /**
     * Converts base-2, base-10, base-16, and binary strings (base-256) to BigIntegers.
     *
     * If the second parameter - $base - is negative, then it will be assumed that the number's are encoded using
     * two's compliment.  The sole exception to this is -10, which is treated the same as 10 is.
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\in base-16
     *
     *    echo $a->toString(); // outputs 50
     * ?>
     * </code>
     *
     * @param $x base-10 number or base-$base number if $base set.
     * @param int $base
     */
    public function __construct($x = 0, $base = 10)
    {
        if(is_resource($x) && get_resource_type($x) == 'GMP integer') {
            $this->value = $x;
            
            return;
        }
        
        $this->value = gmp_init(0);


        // '0' counts as empty() but when the base is 256 '0' is equal to ord('0') or 48
        // '0' is the only value like this per http://php.net/empty
        if (empty($x) && (abs($base) != 256 || $x !== '0')) {

            return;
        }

        switch ($base) {
            case -256:
                if (ord($x[0]) & 0x80) {
                    $x = ~$x;
                    $this->is_negative = true;
                }
            case 256:
                $sign = $this->is_negative ? '-' : '';
                $this->value = gmp_init($sign.'0x'.bin2hex($x));


                if ($this->is_negative) {
                    $this->is_negative = false;
                    $temp = $this->add(new static('-1'));
                    $this->value = $temp->value;
                }
                break;
            case 16:
            case -16:
                if ($base > 0 && $x[0] == '-') {
                    $this->is_negative = true;
                    $x = substr($x, 1);
                }

                $x = preg_replace('#^(?:0x)?([A-Fa-f0-9]*).*#', '$1', $x);

                $is_negative = false;
                if ($base < 0 && hexdec($x[0]) >= 8) {
                    $this->is_negative = $is_negative = true;
                    $x = bin2hex(~hex2bin($x));
                }

            $temp = $this->is_negative ? '-0x'.$x : '0x'.$x;
            $this->value = gmp_init($temp);

            $this->is_negative = false;

                if ($is_negative) {
                    $temp = $this->add(new static('-1'));
                    $this->value = $temp->value;
                }
                break;
            case 10:
            case -10:
                // (?<!^)(?:-).*: find any -'s that aren't at the beginning and then any characters that follow that
                // (?<=^|-)0*: find any 0's that are preceded by the start of the string or by a - (ie. octals)
                // [^-0-9].*: find any non-numeric characters and then any characters that follow that
                $x = preg_replace('#(?<!^)(?:-).*|(?<=^|-)0*|[^-0-9].*#', '', $x);

                $this->value = gmp_init($x);

                break;
            case 2: // base-2 support originally implemented by Lluis Pamies - thanks!
            case -2:
                if ($base > 0 && $x[0] == '-') {
                    $this->is_negative = true;
                    $x = substr($x, 1);
                }

                $x = preg_replace('#^([01]*).*#', '$1', $x);
                $x = str_pad($x, strlen($x) + (3 * strlen($x)) % 4, 0, STR_PAD_LEFT);

                $str = '0x';
                while (strlen($x)) {
                    $part = substr($x, 0, 4);
                    $str .= dechex(bindec($part));
                    $x = substr($x, 4);
                }

                if ($this->is_negative) {
                    $str = '-'.$str;
                }

                $temp = new static($str, 8 * $base); // ie. either -16 or +16
                $this->value = $temp->value;
                $this->is_negative = $temp->is_negative;

                break;
            default:
                // base not supported, so we'll let $this == 0
        }
    }

    /**
     * Converts a BigInteger to a byte string (eg. base-256).
     *
     * Negative numbers are saved as positive numbers, unless $twos_compliment is set to true, at which point, they're
     * saved as two's compliment.
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\ger('65');
     *
     *    echo $a->toBytes(); // outputs chr(65)
     * ?>
     * </code>
     *
     * @param bool $twos_compliment
     *
     * @return string
     *
     */
    public function toBytes($twos_compliment = false)
    {
        if ($twos_compliment) {
            $comparison = $this->compare(new static());
            if ($comparison == 0) {
                return $this->precision > 0 ? str_repeat(chr(0), ($this->precision + 1) >> 3) : '';
            }

            $temp = $comparison < 0 ? $this->add(new static(1)) : $this;
            $bytes = $temp->toBytes();

            if (empty($bytes)) { // eg. if the number we're trying to convert is -1
                $bytes = chr(0);
            }

            if (ord($bytes[0]) & 0x80) {
                $bytes = chr(0).$bytes;
            }

            return $comparison < 0 ? ~$bytes : $bytes;
        }

        if (gmp_cmp($this->value, gmp_init(0)) == 0) {
            return $this->precision > 0 ? str_repeat(chr(0), ($this->precision + 1) >> 3) : '';
        }

        $temp = gmp_strval(gmp_abs($this->value), 16);
        $temp = (strlen($temp) & 1) ? '0'.$temp : $temp;
        $temp = hex2bin($temp);

        return $this->precision > 0 ?
            substr(str_pad($temp, $this->precision >> 3, chr(0), STR_PAD_LEFT), -($this->precision >> 3)) :
            ltrim($temp, chr(0));
    }

    /**
     * Adds two BigIntegers.
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\ger('10');
     *    $b = new \Jose\Util\ger('20');
     *
     *    $c = $a->add($b);
     *
     *    echo $c->toString(); // outputs 30
     * ?>
     * </code>
     *
     * @param \Jose\Util\BigInteger $y
     *
     * @return \Jose\Util\BigInteger
     *
     */
    public function add(BigInteger $y)
    {
        $temp = new static();
        $temp->value = gmp_add($this->value, $y->value);

        return $this->_normalize($temp);
    }

    /**
     * Subtracts two BigIntegers.
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\ger('10');
     *    $b = new \Jose\Util\ger('20');
     *
     *    $c = $a->subtract($b);
     *
     *    echo $c->toString(); // outputs -10
     * ?>
     * </code>
     *
     * @param \Jose\Util\BigInteger $y
     *
     * @return \Jose\Util\BigInteger
     *
     */
    public function subtract(BigInteger $y)
    {
        $temp = new static();
        $temp->value = gmp_sub($this->value, $y->value);

        return $this->_normalize($temp);
    }

    /**
     * Multiplies two BigIntegers.
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\ger('10');
     *    $b = new \Jose\Util\ger('20');
     *
     *    $c = $a->multiply($b);
     *
     *    echo $c->toString(); // outputs 200
     * ?>
     * </code>
     *
     * @param \Jose\Util\BigInteger $x
     *
     * @return \Jose\Util\BigInteger
     */
    public function multiply(BigInteger $x)
    {
        $temp = new static();
        $temp->value = gmp_mul($this->value, $x->value);

        return $this->_normalize($temp);
    }

    /**
     * Divides two BigIntegers.
     *
     * Returns an array whose first element contains the quotient and whose second element contains the
     * "common residue".  If the remainder would be positive, the "common residue" and the remainder are the
     * same.  If the remainder would be negative, the "common residue" is equal to the sum of the remainder
     * and the divisor (basically, the "common residue" is the first positive modulo).
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\ger('10');
     *    $b = new \Jose\Util\ger('20');
     *
     *    list($quotient, $remainder) = $a->divide($b);
     *
     *    echo $quotient->toString(); // outputs 0
     *    echo "\r\n";
     *    echo $remainder->toString(); // outputs 10
     * ?>
     * </code>
     * @param \Jose\Util\BigInteger $y
     *
     * @return \Jose\Util\BigInteger[]
     *
     */
    public function divide(BigInteger $y)
    {
        $quotient = new static();
        $remainder = new static();

        list($quotient->value, $remainder->value) = gmp_div_qr($this->value, $y->value);

        if (gmp_sign($remainder->value) < 0) {
            $remainder->value = gmp_add($remainder->value, gmp_abs($y->value));
        }

        return [$this->_normalize($quotient), $this->_normalize($remainder)];
    }

    /**
     * Performs modular exponentiation.
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\ger('10');
     *    $b = new \Jose\Util\ger('20');
     *    $c = new \Jose\Util\ger('30');
     *
     *    $c = $a->modPow($b, $c);
     *
     *    echo $c->toString(); // outputs 10
     * ?>
     * </code>
     *
     * @param \Jose\Util\BigInteger $e
     * @param \Jose\Util\BigInteger $n
     *
     * @return \Jose\Util\BigInteger
     *
     *    and although the approach involving repeated squaring does vastly better, it, too, is impractical
     *    for our purposes.  The reason being that division - by far the most complicated and time-consuming
     *    of the basic operations (eg. +,-,*,/) - occurs multiple times within it.
     *
     *    Modular reductions resolve this issue.  Although an individual modular reduction takes more time
     *    then an individual division, when performed in succession (with the same modulo), they're a lot faster.
     *
     *    The two most commonly used modular reductions are Barrett and Montgomery reduction.  Montgomery reduction,
     *    although faster, only works when the gcd of the modulo and of the base being used is 1.  In RSA, when the
     *    base is a power of two, the modulo - a product of two primes - is always going to have a gcd of 1 (because
     *    the product of two odd numbers is odd), but what about when RSA isn't used?
     *
     *    In contrast, Barrett reduction has no such constraint.  As such, some bigint implementations perform a
     *    Barrett reduction after every operation in the modpow function.  Others perform Barrett reductions when the
     *    modulo is even and Montgomery reductions when the modulo is odd.  BigInteger.java's modPow method, however,
     *    uses a trick involving the Chinese Remainder Theorem to factor the even modulo into two numbers - one odd and
     *    the other, a power of two - and recombine them, later.  This is the method that this modPow function uses.
     *    {@link http://islab.oregonstate.edu/papers/j34monex.pdf Montgomery Reduction with Even Modulus} elaborates.
     */
    public function modPow(BigInteger $e, BigInteger $n)
    {
        $n = $this->bitmask !== false && $this->bitmask->compare($n) < 0 ? $this->bitmask : $n->abs();


        if ($e->compare(new static()) < 0) {
            $e = $e->abs();

            $temp = $this->modInverse($n);
/**
 * @return array|string
 */
function returnsDifferentValues($x) {
    if ($x) {
        return 'foo';
    }

    return array();
}

$x = returnsDifferentValues($y);
if (is_array($x)) {
    // $x is an array.
}
            if ($temp === false) {
                return false;
class Author {
    private $name;

    public function __construct($name) {
        $this->name = $name;
    }

    public function getName() {
        return $this->name;
    }
}

abstract class Post {
    public function getAuthor() {
        return 'Johannes';
    }
}

class BlogPost extends Post {
    public function getAuthor() {
        return new Author('Johannes');
    }
}

class ForumPost extends Post { /* ... */ }

function my_function(Post $post) {
    echo strtoupper($post->getAuthor());
}
            }

            return $this->_normalize($temp->modPow($e, $n));
/**
 * @return array|string
 */
function returnsDifferentValues($x) {
    if ($x) {
        return 'foo';
    }

    return array();
}

$x = returnsDifferentValues($y);
if (is_array($x)) {
    // $x is an array.
}
        }

            $temp = new static();
            $temp->value = gmp_powm($this->value, $e->value, $n->value);

            return $this->_normalize($temp);
    }

    /**
     * Calculates modular inverses.
     *
     * Say you have (30 mod 17 * x mod 17) mod 17 == 1.  x can be found using modular inverses.
     *
     * Here's an example:
     * <code>
     * <?php
     *    $a = new \Jose\Util\teger(30);
     *    $b = new \Jose\Util\teger(17);
     *
     *    $c = $a->modInverse($b);
     *    echo $c->toString(); // outputs 4
     *
     *    echo "\r\n";
     *
     *    $d = $a->multiply($c);
     *    list(, $d) = $d->divide($b);
     *    echo $d; // outputs 1 (as per the definition of modular inverse)
     * ?>
     * </code>
     *
     * @param \Jose\Util\BigInteger $n
     *
     * @return \Jose\Util\BigInteger|bool
     *
     */
    public function modInverse(BigInteger $n)
    {
        $temp = new static();
        $temp->value = gmp_invert($this->value, $n->value);

        return ($temp->value === false) ? false : $this->_normalize($temp);
    }

    /**
     * Absolute value.
     *
     * @return \Jose\Util\BigInteger
     */
    public function abs()
    {
        $temp = new static();

        $temp->value = gmp_abs($this->value);

        return $temp;
    }

    /**
     * Compares two numbers.
     *
     * Although one might think !$x->compare($y) means $x != $y, it, in fact, means the opposite.  The reason for this is
     * demonstrated thusly:
     *
     * $x  > $y: $x->compare($y)  > 0
     * $x  < $y: $x->compare($y)  < 0
     * $x == $y: $x->compare($y) == 0
     *
     * Note how the same comparison operator is used.  If you want to test for equality, use $x->equals($y).
     *
     * @param \Jose\Util\BigInteger $y
     *
     * @return int < 0 if $this is less than $y; > 0 if $this is greater than $y, and 0 if they are equal.
     *
     */
    public function compare(BigInteger $y)
    {
        return gmp_cmp($this->value, $y->value);
    }

    /**
     * Logical Left Shift.
     *
     * Shifts BigInteger's by $shift bits, effectively multiplying by 2**$shift.
     *
     * @param int $shift
     *
     * @return \Jose\Util\BigInteger
     *
     */
    public function bitwise_leftShift($shift)
    {
        $temp = new static();

        static $two;

        if (!isset($two)) {
            $two = gmp_init('2');
        }

        $temp->value = gmp_mul($this->value, gmp_pow($two, $shift));

        return $this->_normalize($temp);
    }

    /**
     * Generates a random BigInteger.
     *
     * Byte length is equal to $length. Uses \phpseclib\Crypt\Random if it's loaded and mt_rand if it's not.
     *
     * @param int $size
     *
     * @return \Jose\Util\BigInteger
     */
    private static function _random_number_helper($size)
    {
        return new static(random_bytes($size), 256);
    }

    /**
     * Generate a random number.
     *
     * Returns a random number between $min and $max where $min and $max
     * can be defined using one of the two methods:
     *
     * BigInteger::random($min, $max)
     * BigInteger::random($max, $min)
     *
     * @param \Jose\Util\BigInteger $min
     * @param \Jose\Util\BigInteger $max
     *
     * @return \Jose\Util\BigInteger
     */
    public static function random(BigInteger $min, BigInteger $max)
    {
        $compare = $max->compare($min);

        if (!$compare) {
            return $this->_normalize($min);

        } elseif ($compare < 0) {
            // if $min is bigger then $max, swap $min and $max
            $temp = $max;
            $max = $min;
            $min = $temp;
        }

        static $one;
        if (!isset($one)) {
            $one = new static(1);
        }

        $max = $max->subtract($min->subtract($one));
        $size = strlen(ltrim($max->toBytes(), chr(0)));

        /*
            doing $random % $max doesn't work because some numbers will be more likely to occur than others.
            eg. if $max is 140 and $random's max is 255 then that'd mean both $random = 5 and $random = 145
            would produce 5 whereas the only value of random that could produce 139 would be 139. ie.
            not all numbers would be equally likely. some would be more likely than others.

            creating a whole new random number until you find one that is within the range doesn't work
            because, for sufficiently small ranges, the likelihood that you'd get a number within that range
            would be pretty small. eg. with $random's max being 255 and if your $max being 1 the probability
            would be pretty high that $random would be greater than $max.

            phpseclib works around this using the technique described here:

            http://crypto.stackexchange.com/questions/5708/creating-a-small-number-from-a-cryptographically-secure-random-string
        */
        $random_max = new static(chr(1).str_repeat("\0", $size), 256);
        $random = self::_random_number_helper($size);

        list($max_multiple) = $random_max->divide($max);
        $max_multiple = $max_multiple->multiply($max);

        while ($random->compare($max_multiple) >= 0) {
            $random = $random->subtract($max_multiple);
            $random_max = $random_max->subtract($max_multiple);
            $random = $random->bitwise_leftShift(8);
            $random = $random->add(self::_random_number_helper(1));
            $random_max = $random_max->bitwise_leftShift(8);
            list($max_multiple) = $random_max->divide($max);
            $max_multiple = $max_multiple->multiply($max);
        }
        list(, $random) = $random->divide($max);

        return $random->add($min);
    }

    /**
     * Normalize.
     *
     * Removes leading zeros and truncates (if necessary) to maintain the appropriate precision
     *
     * @param \Jose\Util\BigInteger $result
     *
     * @return \Jose\Util\BigInteger
     */
    private function _normalize($result)
    {
        $result->precision = $this->precision;
        $result->bitmask = $this->bitmask;

        if ($this->bitmask !== false) {
            $result->value = gmp_and($result->value, $result->bitmask->value);
        }

        return $result;
    }
}

Spomky-Labs / jose

Push — PHPSecLib_Rid ( 32d4bc...6a2b08 )

BigInteger::modPow() B

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