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<?php
/**
* Base BigInteger Engine
*
* PHP version 5 and 7
*
* @category Math
* @package BigInteger
* @author Jim Wigginton <terrafrost@php.net>
* @copyright 2017 Jim Wigginton
* @license http://www.opensource.org/licenses/mit-license.html MIT License
* @link http://pear.php.net/package/Math_BigInteger
*/
namespace phpseclib3\Math\BigInteger\Engines;
use ParagonIE\ConstantTime\Hex;
use phpseclib3\Exception\BadConfigurationException;
use phpseclib3\Crypt\Random;
use phpseclib3\Math\BigInteger;
use phpseclib3\Common\Functions\Strings;
/**
* Base Engine.
*
* @package Engine
* @author Jim Wigginton <terrafrost@php.net>
* @access public
*/
abstract class Engine implements \Serializable
{
/**
* Holds the BigInteger's value
*
* @var mixed
*/
protected $value;
/**
* Holds the BigInteger's sign
*
* @var bool
*/
protected $is_negative;
/**
* Precision
*
* @see static::setPrecision()
*/
protected $precision = -1;
/**
* Precision Bitmask
*
* @see static::setPrecision()
*/
protected $bitmask = false;
/**
* Recurring Modulo Function
*
* @var callable
*/
protected $reduce;
/**
* Default constructor
*
* @param mixed $x integer Base-10 number or base-$base number if $base set.
* @param int $base
*/
public function __construct($x, $base)
{
if (!isset(static::$primes)) {
static::$primes = [
3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59,
61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137,
139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227,
229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313,
317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419,
421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509,
521, 523, 541, 547, 557, 563, 569, 571, 577, 587, 593, 599, 601, 607, 613, 617,
619, 631, 641, 643, 647, 653, 659, 661, 673, 677, 683, 691, 701, 709, 719, 727,
733, 739, 743, 751, 757, 761, 769, 773, 787, 797, 809, 811, 821, 823, 827, 829,
839, 853, 857, 859, 863, 877, 881, 883, 887, 907, 911, 919, 929, 937, 941, 947,
953, 967, 971, 977, 983, 991, 997
];
static::$zero = new static(0);
static::$one = new static(1);
static::$two = new static(2);
}
// '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:
case 256:
if ($base == -256 && (ord($x[0]) & 0x80)) {
$this->value = ~$x;
$this->is_negative = true;
} else {
$this->value = $x;
$this->is_negative = false;
}
static::initialize($base);
if ($this->is_negative) {
$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;
$x = Hex::encode(~Hex::decode($x));
}
$this->value = $x;
static::initialize($base);
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
$this->value = preg_replace('#(?<!^)(?:-).*|(?<=^|-)0*|[^-0-9].*#', '', $x);
if (!strlen($this->value) || $this->value == '-') {
$this->value = '0';
}
static::initialize($base);
break;
case -2:
case 2:
if ($base > 0 && $x[0] == '-') {
$this->is_negative = true;
$x = substr($x, 1);
}
$x = preg_replace('#^([01]*).*#', '$1', $x);
$temp = new static(Strings::bits2bin($x), 128 * $base); // ie. either -16 or +16
$this->value = $temp->value;
if ($temp->is_negative) {
$this->is_negative = true;
}
break;
default:
// base not supported, so we'll let $this == 0
}
}
/**
* Sets engine type.
*
* Throws an exception if the type is invalid
*
* @param string $engine
*/
public static function setModExpEngine($engine)
{
$fqengine = '\\phpseclib3\\Math\\BigInteger\\Engines\\' . static::ENGINE_DIR . '\\' . $engine;
if (!class_exists($fqengine) || !method_exists($fqengine, 'isValidEngine')) {
throw new \InvalidArgumentException("$engine is not a valid engine");
}
if (!$fqengine::isValidEngine()) {
throw new BadConfigurationException("$engine is not setup correctly on this system");
}
static::$modexpEngine = $fqengine;
}
/**
* 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.
* @return string
*/
protected function toBytesHelper()
{
$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 = $temp->toBytes();
if (!strlen($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;
}
/**
* Converts a BigInteger to a hex string (eg. base-16).
*
* @param bool $twos_compliment
* @return string
*/
public function toHex($twos_compliment = false)
{
return Hex::encode($this->toBytes($twos_compliment));
}
/**
* Converts a BigInteger to a bit string (eg. base-2).
*
* Negative numbers are saved as positive numbers, unless $twos_compliment is set to true, at which point, they're
* saved as two's compliment.
*
* @param bool $twos_compliment
* @return string
*/
public function toBits($twos_compliment = false)
{
$hex = $this->toBytes($twos_compliment);
$bits = Strings::bin2bits($hex);
$result = $this->precision > 0 ? substr($bits, -$this->precision) : ltrim($bits, '0');
if ($twos_compliment && $this->compare(new static()) > 0 && $this->precision <= 0) {
return '0' . $result;
}
return $result;
}
/**
* Calculates modular inverses.
*
* Say you have (30 mod 17 * x mod 17) mod 17 == 1. x can be found using modular inverses.
*
* {@internal See {@link http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf#page=21 HAC 14.64} for more information.}
*
* @param \phpseclib3\Math\BigInteger\Engines\Engine $n
* @return \phpseclib3\Math\BigInteger\Engines\Engine|false
*/
protected function modInverseHelper(Engine $n)
{
// $x mod -$n == $x mod $n.
$n = $n->abs();
if ($this->compare(static::$zero) < 0) {
$temp = $this->abs();
$temp = $temp->modInverse($n);
return $this->normalize($n->subtract($temp));
}
extract($this->extendedGCD($n));
/**
* @var BigInteger $gcd
* @var BigInteger $x
*/
if (!$gcd->equals(static::$one)) {
return false;
}
$x = $x->compare(static::$zero) < 0 ? $x->add($n) : $x;
return $this->compare(static::$zero) < 0 ? $this->normalize($n->subtract($x)) : $this->normalize($x);
}
/**
* Serialize
*
* Will be called, automatically, when serialize() is called on a BigInteger object.
*
* @return string
*/
public function serialize()
{
$val = ['hex' => $this->toHex(true)];
if ($this->precision > 0) {
$val['precision'] = $this->precision;
}
return serialize($val);
}
/**
* Serialize
*
* Will be called, automatically, when unserialize() is called on a BigInteger object.
*
* @param string $serialized
*/
public function unserialize($serialized)
{
$r = unserialize($serialized);
$temp = new static($r['hex'], -16);
$this->value = $temp->value;
$this->is_negative = $temp->is_negative;
if (isset($r['precision'])) {
// recalculate $this->bitmask
$this->setPrecision($r['precision']);
}
}
/**
* Converts a BigInteger to a base-10 number.
*
* @return string
*/
public function __toString()
{
return $this->toString();
}
/**
* __debugInfo() magic method
*
* Will be called, automatically, when print_r() or var_dump() are called
*/
public function __debugInfo()
{
return [
'value' => '0x' . $this->toHex(true),
'engine' => basename(static::class)
];
}
/**
* Set Precision
*
* Some bitwise operations give different results depending on the precision being used. Examples include left
* shift, not, and rotates.
*
* @param int $bits
*/
public function setPrecision($bits)
{
if ($bits < 1) {
$this->precision = -1;
$this->bitmask = false;
return;
}
$this->precision = $bits;
$this->bitmask = static::setBitmask($bits);
$temp = $this->normalize($this);
$this->value = $temp->value;
}
/**
* Get Precision
*
* Returns the precision if it exists, -1 if it doesn't
*
* @return int
*/
public function getPrecision()
{
return $this->precision;
}
/**
* Set Bitmask
* @return Engine
* @param int $bits
* @see self::setPrecision()
*/
protected static function setBitmask($bits)
{
return new static(chr((1 << ($bits & 0x7)) - 1) . str_repeat(chr(0xFF), $bits >> 3), 256);
}
/**
* Logical Not
*
* @return Engine|string
*/
public function bitwise_not()
{
// calculuate "not" without regard to $this->precision
// (will always result in a smaller number. ie. ~1 isn't 1111 1110 - it's 0)
$temp = $this->toBytes();
if ($temp == '') {
return $this->normalize(static::$zero);
}
$pre_msb = decbin(ord($temp[0]));
$temp = ~$temp;
$msb = decbin(ord($temp[0]));
if (strlen($msb) == 8) {
$msb = substr($msb, strpos($msb, '0'));
}
$temp[0] = chr(bindec($msb));
// see if we need to add extra leading 1's
$current_bits = strlen($pre_msb) + 8 * strlen($temp) - 8;
$new_bits = $this->precision - $current_bits;
if ($new_bits <= 0) {
return $this->normalize(new static($temp, 256));
}
// generate as many leading 1's as we need to.
$leading_ones = chr((1 << ($new_bits & 0x7)) - 1) . str_repeat(chr(0xFF), $new_bits >> 3);
self::base256_lshift($leading_ones, $current_bits);
$temp = str_pad($temp, strlen($leading_ones), chr(0), STR_PAD_LEFT);
return $this->normalize(new static($leading_ones | $temp, 256));
}
/**
* Logical Left Shift
*
* Shifts binary strings $shift bits, essentially multiplying by 2**$shift.
*
* @param string $x
* @param int $shift
* @return string
*/
protected static function base256_lshift(&$x, $shift)
{
if ($shift == 0) {
return;
}
$num_bytes = $shift >> 3; // eg. floor($shift/8)
$shift &= 7; // eg. $shift % 8
$carry = 0;
for ($i = strlen($x) - 1; $i >= 0; --$i) {
$temp = ord($x[$i]) << $shift | $carry;
$x[$i] = chr($temp);
$carry = $temp >> 8;
}
$carry = ($carry != 0) ? chr($carry) : '';
$x = $carry . $x . str_repeat(chr(0), $num_bytes);
}
/**
* Logical Left Rotate
*
* Instead of the top x bits being dropped they're appended to the shifted bit string.
*
* @param int $shift
* @return \phpseclib3\Math\BigInteger\Engines\Engine
*/
public function bitwise_leftRotate($shift)
{
$bits = $this->toBytes();
if ($this->precision > 0) {
$precision = $this->precision;
if (static::FAST_BITWISE) {
$mask = $this->bitmask->toBytes();
} else {
$mask = $this->bitmask->subtract(new static(1));
$mask = $mask->toBytes();
}
} else {
$temp = ord($bits[0]);
for ($i = 0; $temp >> $i; ++$i) {
}
$precision = 8 * strlen($bits) - 8 + $i;
$mask = chr((1 << ($precision & 0x7)) - 1) . str_repeat(chr(0xFF), $precision >> 3);
}
if ($shift < 0) {
$shift+= $precision;
}
$shift%= $precision;
if (!$shift) {
return clone $this;
}
$left = $this->bitwise_leftShift($shift);
$left = $left->bitwise_and(new static($mask, 256));
$right = $this->bitwise_rightShift($precision - $shift);
$result = static::FAST_BITWISE ? $left->bitwise_or($right) : $left->add($right);
return $this->normalize($result);
}
/**
* Logical Right Rotate
*
* Instead of the bottom x bits being dropped they're prepended to the shifted bit string.
*
* @param int $shift
* @return \phpseclib3\Math\BigInteger\Engines\Engine
*/
public function bitwise_rightRotate($shift)
{
return $this->bitwise_leftRotate(-$shift);
}
/**
* Returns the smallest and largest n-bit number
*
* @param int $bits
* @return \phpseclib3\Math\BigInteger\Engines\Engine[]
*/
public static function minMaxBits($bits)
{
$bytes = $bits >> 3;
$min = str_repeat(chr(0), $bytes);
$max = str_repeat(chr(0xFF), $bytes);
$msb = $bits & 7;
if ($msb) {
$min = chr(1 << ($msb - 1)) . $min;
$max = chr((1 << $msb) - 1) . $max;
} else {
$min[0] = chr(0x80);
}
return [
'min' => new static($min, 256),
'max' => new static($max, 256)
];
}
/**
* Return the size of a BigInteger in bits
*
* @return int
*/
public function getLength()
{
return strlen($this->toBits());
}
/**
* Return the size of a BigInteger in bytes
*
* @return int
*/
public function getLengthInBytes()
{
return strlen($this->toBytes());
}
/**
* Performs some pre-processing for powMod
*
* @param Engine $e
* @param Engine $n
* @return bool|Engine
*/
protected function powModOuter(Engine $e, Engine $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);
if ($temp === false) {
return false;
}
return $this->normalize($temp->powModInner($e, $n));
}
return $this->powModInner($e, $n);
}
/**
* Sliding Window k-ary Modular Exponentiation
*
* Based on {@link http://www.cacr.math.uwaterloo.ca/hac/about/chap14.pdf#page=27 HAC 14.85} /
* {@link http://math.libtomcrypt.com/files/tommath.pdf#page=210 MPM 7.7}. In a departure from those algorithims,
* however, this function performs a modular reduction after every multiplication and squaring operation.
* As such, this function has the same preconditions that the reductions being used do.
*
* @param \phpseclib3\Math\BigInteger\Engines\Engine $x
* @param \phpseclib3\Math\BigInteger\Engines\Engine $e
* @param \phpseclib3\Math\BigInteger\Engines\Engine $n
* @param string $class
* @return \phpseclib3\Math\BigInteger\Engines\Engine
*/
protected static function slidingWindow(Engine $x, Engine $e, Engine $n, $class)
{
static $window_ranges = [7, 25, 81, 241, 673, 1793]; // from BigInteger.java's oddModPow function
//static $window_ranges = [0, 7, 36, 140, 450, 1303, 3529]; // from MPM 7.3.1
$e_bits = $e->toBits();
$e_length = strlen($e_bits);
// calculate the appropriate window size.
// $window_size == 3 if $window_ranges is between 25 and 81, for example.
for ($i = 0, $window_size = 1; $i < count($window_ranges) && $e_length > $window_ranges[$i]; ++$window_size, ++$i) {
}
$n_value = $n->value;
if (method_exists(static::class, 'generateCustomReduction')) {
static::generateCustomReduction($n, $class);
}
// precompute $this^0 through $this^$window_size
$powers = [];
$powers[1] = static::prepareReduce($x->value, $n_value, $class);
$powers[2] = static::squareReduce($powers[1], $n_value, $class);
// we do every other number since substr($e_bits, $i, $j+1) (see below) is supposed to end
// in a 1. ie. it's supposed to be odd.
$temp = 1 << ($window_size - 1);
for ($i = 1; $i < $temp; ++$i) {
$i2 = $i << 1;
$powers[$i2 + 1] = static::multiplyReduce($powers[$i2 - 1], $powers[2], $n_value, $class);
}
$result = new $class(1);
$result = static::prepareReduce($result->value, $n_value, $class);
for ($i = 0; $i < $e_length;) {
if (!$e_bits[$i]) {
$result = static::squareReduce($result, $n_value, $class);
++$i;
} else {
for ($j = $window_size - 1; $j > 0; --$j) {
if (!empty($e_bits[$i + $j])) {
break;
}
}
// eg. the length of substr($e_bits, $i, $j + 1)
for ($k = 0; $k <= $j; ++$k) {
$result = static::squareReduce($result, $n_value, $class);
}
$result = static::multiplyReduce($result, $powers[bindec(substr($e_bits, $i, $j + 1))], $n_value, $class);
$i += $j + 1;
}
}
$temp = new $class();
$temp->value = static::reduce($result, $n_value, $class);
return $temp;
}
/**
* Generates a random number of a certain size
*
* Bit length is equal to $size
*
* @param int $size
* @return \phpseclib3\Math\BigInteger\Engines\Engine
*/
public static function random($size)
{
extract(static::minMaxBits($size));
/**
* @var BigInteger $min
* @var BigInteger $max
*/
return static::randomRange($min, $max);
}
/**
* Generates a random prime number of a certain size
*
* Bit length is equal to $size
*
* @param int $size
* @return \phpseclib3\Math\BigInteger\Engines\Engine
*/
public static function randomPrime($size)
{
extract(static::minMaxBits($size));
/**
* @var BigInteger $min
* @var BigInteger $max
*/
return static::randomRangePrime($min, $max);
}
/**
* Performs some pre-processing for randomRangePrime
*
* @param Engine $min
* @param Engine $max
* @return bool|Engine
*/
protected static function randomRangePrimeOuter(Engine $min, Engine $max)
{
$compare = $max->compare($min);
if (!$compare) {
return $min->isPrime() ? $min : false;
} elseif ($compare < 0) {
// if $min is bigger then $max, swap $min and $max
$temp = $max;
$max = $min;
$min = $temp;
}
$x = static::randomRange($min, $max);
return static::randomRangePrimeInner($x, $min, $max);
}
/**
* Generate a random number between a range
*
* Returns a random number between $min and $max where $min and $max
* can be defined using one of the two methods:
*
* BigInteger::randomRange($min, $max)
* BigInteger::randomRange($max, $min)
*
* @param Engine $min
* @param Engine $max
* @return Engine
*/
protected static function randomRangeHelper(Engine $min, Engine $max)
{
$compare = $max->compare($min);
if (!$compare) {
return $min;
} elseif ($compare < 0) {
// if $min is bigger then $max, swap $min and $max
$temp = $max;
$max = $min;
$min = $temp;
}
if (!isset(static::$one)) {
static::$one = new static(1);
}
$max = $max->subtract($min->subtract(static::$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);
$random = new static(Random::string($size), 256);
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(new static(Random::string(1), 256));
$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);
}
/**
* Performs some post-processing for randomRangePrime
*
* @param Engine $x
* @param Engine $min
* @param Engine $max
* @return bool|Engine
*/
protected static function randomRangePrimeInner(Engine $x, Engine $min, Engine $max)
{
if (!isset(static::$two)) {
static::$two = new static('2');
}
$x->make_odd();
if ($x->compare($max) > 0) {
// if $x > $max then $max is even and if $min == $max then no prime number exists between the specified range
if ($min->equals($max)) {
return false;
}
$x = clone $min;
$x->make_odd();
}
$initial_x = clone $x;
while (true) {
if ($x->isPrime()) {
return $x;
}
$x = $x->add(static::$two);
if ($x->compare($max) > 0) {
$x = clone $min;
if ($x->equals(static::$two)) {
return $x;
}
$x->make_odd();
}
if ($x->equals($initial_x)) {
return false;
}
}
}
/**
* Sets the $t parameter for primality testing
*
* @return int
*/
protected function setupIsPrime()
{
$length = $this->getLengthInBytes();
// see HAC 4.49 "Note (controlling the error probability)"
// @codingStandardsIgnoreStart
if ($length >= 163) { $t = 2; } // floor(1300 / 8)
else if ($length >= 106) { $t = 3; } // floor( 850 / 8)
else if ($length >= 81 ) { $t = 4; } // floor( 650 / 8)
else if ($length >= 68 ) { $t = 5; } // floor( 550 / 8)
else if ($length >= 56 ) { $t = 6; } // floor( 450 / 8)
else if ($length >= 50 ) { $t = 7; } // floor( 400 / 8)
else if ($length >= 43 ) { $t = 8; } // floor( 350 / 8)
else if ($length >= 37 ) { $t = 9; } // floor( 300 / 8)
else if ($length >= 31 ) { $t = 12; } // floor( 250 / 8)
else if ($length >= 25 ) { $t = 15; } // floor( 200 / 8)
else if ($length >= 18 ) { $t = 18; } // floor( 150 / 8)
else { $t = 27; }
// @codingStandardsIgnoreEnd
return $t;
}
/**
* Tests Primality
*
* Uses the {@link http://en.wikipedia.org/wiki/Miller%E2%80%93Rabin_primality_test Miller-Rabin primality test}.
* See {@link http://www.cacr.math.uwaterloo.ca/hac/about/chap4.pdf#page=8 HAC 4.24} for more info.
*
* @param int $t
* @return bool
*/
protected function testPrimality($t)
{
if (!$this->testSmallPrimes()) {
return false;
}
$n = clone $this;
$n_1 = $n->subtract(static::$one);
$n_2 = $n->subtract(static::$two);
$r = clone $n_1;
$s = static::scan1divide($r);
for ($i = 0; $i < $t; ++$i) {
$a = static::randomRange(static::$two, $n_2);
$y = $a->modPow($r, $n);
if (!$y->equals(static::$one) && !$y->equals($n_1)) {
for ($j = 1; $j < $s && !$y->equals($n_1); ++$j) {
$y = $y->modPow(static::$two, $n);
if ($y->equals(static::$one)) {
return false;
}
}
if (!$y->equals($n_1)) {
return false;
}
}
}
return true;
}
/**
* Checks a numer to see if it's prime
*
* Assuming the $t parameter is not set, this function has an error rate of 2**-80. The main motivation for the
* $t parameter is distributability. BigInteger::randomPrime() can be distributed across multiple pageloads
* on a website instead of just one.
*
* @param int|bool $t
* @return bool
*/
public function isPrime($t = false)
{
if (!$t) {
$t = $this->setupIsPrime();
}
return $this->testPrimality($t);
}
/**
* Performs a few preliminary checks on root
*
* @param int $n
* @return \phpseclib3\Math\BigInteger\Engines\Engine
*/
protected function rootHelper($n)
{
if ($n < 1) {
return clone static::$zero;
} // we want positive exponents
if ($this->compare(static::$one) < 0) {
return clone static::$zero;
} // we want positive numbers
if ($this->compare(static::$two) < 0) {
return clone static::$one;
} // n-th root of 1 or 2 is 1
return $this->rootInner($n);
}
/**
* Calculates the nth root of a biginteger.
*
* Returns the nth root of a positive biginteger, where n defaults to 2
*
* {@internal This function is based off of {@link http://mathforum.org/library/drmath/view/52605.html this page} and {@link http://stackoverflow.com/questions/11242920/calculating-nth-root-with-bcmath-in-php this stackoverflow question}.}
*
* @param int $n
* @return \phpseclib3\Math\BigInteger\Engines\Engine
*/
protected function rootInner($n)
{
$n = new static($n);
// g is our guess number
$g = static::$two;
// while (g^n < num) g=g*2
while ($g->pow($n)->compare($this) < 0) {
$g = $g->multiply(static::$two);
}
// if (g^n==num) num is a power of 2, we're lucky, end of job
// == 0 bccomp(bcpow($g, $n), $n->value)==0
if ($g->pow($n)->equals($this) > 0) {
$root = $g;
return $this->normalize($root);
}
// if we're here num wasn't a power of 2 :(
$og = $g; // og means original guess and here is our upper bound
$g = $g->divide(static::$two)[0]; // g is set to be our lower bound
$step = $og->subtract($g)->divide(static::$two)[0]; // step is the half of upper bound - lower bound
$g = $g->add($step); // we start at lower bound + step , basically in the middle of our interval
// while step>1
while ($step->compare(static::$one) == 1) {
$guess = $g->pow($n);
$step = $step->divide(static::$two)[0];
$comp = $guess->compare($this); // compare our guess with real number
switch ($comp) {
case -1: // if guess is lower we add the new step
$g = $g->add($step);
break;
case 1: // if guess is higher we sub the new step
$g = $g->subtract($step);
break;
case 0: // if guess is exactly the num we're done, we return the value
$root = $g;
break 2;
}
}
if ($comp == 1) {
$g = $g->subtract($step);
}
// whatever happened, g is the closest guess we can make so return it
$root = $g;
return $this->normalize($root);
}
/**
* Calculates the nth root of a biginteger.
*
* @param int $n
* @return Engine
*/
public function root($n = 2)
{
return $this->rootHelper($n);
}
/**
* Return the minimum BigInteger between an arbitrary number of BigIntegers.
*
* @param array $nums
* @return Engine
*/
protected static function minHelper(array $nums)
{
if (count($nums) == 1) {
return $nums[0];
}
$min = $nums[0];
for ($i = 1; $i < count($nums); $i++) {
$min = $min->compare($nums[$i]) > 0 ? $nums[$i] : $min;
}
return $min;
}
/**
* Return the minimum BigInteger between an arbitrary number of BigIntegers.
*
* @param array $nums
* @return Engine
*/
protected static function maxHelper(array $nums)
{
if (count($nums) == 1) {
return $nums[0];
}
$max = $nums[0];
for ($i = 1; $i < count($nums); $i++) {
$max = $max->compare($nums[$i]) < 0 ? $nums[$i] : $max;
}
return $max;
}
/**
* Create Recurring Modulo Function
*
* Sometimes it may be desirable to do repeated modulos with the same number outside of
* modular exponentiation
*
* @return callable
*/
public function createRecurringModuloFunction()
{
$class = static::class;
$fqengine = !method_exists(static::$modexpEngine, 'reduce') ?
'\\phpseclib3\\Math\\BigInteger\\Engines\\' . static::ENGINE_DIR . '\\DefaultEngine' :
static::$modexpEngine;
if (method_exists($fqengine, 'generateCustomReduction')) {
$func = $fqengine::generateCustomReduction($this, static::class);
$this->reduce = eval('return function(' . static::class . ' $x) use ($func, $class) {
$r = new $class();
$r->value = $func($x->value);
return $r;
};');
return clone $this->reduce;
}
$n = $this->value;
$this->reduce = eval('return function(' . static::class . ' $x) use ($n, $fqengine, $class) {
$r = new $class();
$r->value = $fqengine::reduce($x->value, $n, $class);
return $r;
};');
return clone $this->reduce;
}
/**
* Calculates the greatest common divisor and Bezout's identity.
*
* @param Engine $n
* @param Engine $stop (optional)
* @return Engine
*/
protected function extendedGCDHelper(Engine $n, Engine $stop = null)
{
$u = clone $this;
$v = clone $n;
$one = new static(1);
$zero = new static();
$a = clone $one;
$b = clone $zero;
$c = clone $zero;
$d = clone $one;
while (!$v->equals($zero)) {
list($q) = $u->divide($v);
$temp = $u;
$u = $v;
$v = $temp->subtract($v->multiply($q));
$temp = $a;
$a = $c;
$c = $temp->subtract($a->multiply($q));
$temp = $b;
$b = $d;
$d = $temp->subtract($b->multiply($q));
}
return [
'gcd'=> $u,
'x' => $a,
'y' => $b
];
}
/**
* Bitwise Split
*
* Splits BigInteger's into chunks of $split bits
*
* @param int $split
* @return \phpseclib3\Math\BigInteger\Engines\Engine[]
*/
public function bitwise_split($split)
{
if ($split < 1) {
throw new \RuntimeException('Offset must be greater than 1');
}
$mask = static::$one->bitwise_leftShift($split)->subtract(static::$one);
$num = clone $this;
$vals = [];
while (!$num->equals(static::$zero)) {
$vals[] = $num->bitwise_and($mask);
$num = $num->bitwise_rightShift($split);
}
return array_reverse($vals);
}
/**
* Logical And
*
* @param Engine $x
* @return Engine
*/
protected function bitwiseAndHelper(Engine $x)
{
$left = $this->toBytes(true);
$right = $x->toBytes(true);
$length = max(strlen($left), strlen($right));
$left = str_pad($left, $length, chr(0), STR_PAD_LEFT);
$right = str_pad($right, $length, chr(0), STR_PAD_LEFT);
return $this->normalize(new static($left & $right, -256));
}
/**
* Logical Or
*
* @param Engine $x
* @return Engine
*/
protected function bitwiseOrHelper(Engine $x)
{
$left = $this->toBytes(true);
$right = $x->toBytes(true);
$length = max(strlen($left), strlen($right));
$left = str_pad($left, $length, chr(0), STR_PAD_LEFT);
$right = str_pad($right, $length, chr(0), STR_PAD_LEFT);
return $this->normalize(new static($left | $right, -256));
}
/**
* Logical Exclusive Or
*
* @param Engine $x
* @return Engine
*/
protected function bitwiseXorHelper(Engine $x)
{
$left = $this->toBytes(true);
$right = $x->toBytes(true);
$length = max(strlen($left), strlen($right));
$left = str_pad($left, $length, chr(0), STR_PAD_LEFT);
$right = str_pad($right, $length, chr(0), STR_PAD_LEFT);
return $this->normalize(new static($left ^ $right, -256));
}
}
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