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BigInteger
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BCMath
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Base.php
90 lines
| 1 | <?php |
| 2 | |
| 3 | /** |
| 4 | * Modular Exponentiation Engine |
| 5 | * |
| 6 | * PHP version 5 and 7 |
| 7 | * |
| 8 | * @author Jim Wigginton <terrafrost@php.net> |
| 9 | * @copyright 2017 Jim Wigginton |
| 10 | * @license http://www.opensource.org/licenses/mit-license.html MIT License |
| 11 | * @link http://pear.php.net/package/Math_BigInteger |
| 12 | */ |
| 13 | |
| 14 | declare(strict_types=1); |
| 15 | |
| 16 | namespace phpseclib3\Math\BigInteger\Engines\BCMath; |
| 17 | |
| 18 | use phpseclib3\Math\BigInteger\Engines\BCMath; |
| 19 | |
| 20 | /** |
| 21 | * Sliding Window Exponentiation Engine |
| 22 | * |
| 23 | * @author Jim Wigginton <terrafrost@php.net> |
| 24 | */ |
| 25 | abstract class Base extends BCMath |
| 26 | { |
| 27 | /** |
| 28 | * Cache constants |
| 29 | * |
| 30 | * $cache[self::VARIABLE] tells us whether or not the cached data is still valid. |
| 31 | */ |
| 32 | public const VARIABLE = 0; |
| 33 | /** |
| 34 | * $cache[self::DATA] contains the cached data. |
| 35 | */ |
| 36 | public const DATA = 1; |
| 37 | |
| 38 | /** |
| 39 | * Test for engine validity |
| 40 | */ |
| 41 | public static function isValidEngine(): bool |
| 42 | { |
| 43 | return static::class != __CLASS__; |
| 44 | } |
| 45 | |
| 46 | /** |
| 47 | * Performs modular exponentiation. |
| 48 | */ |
| 49 | protected static function powModHelper(BCMath $x, BCMath $e, BCMath $n, string $class): BCMath |
| 50 | { |
| 51 | if (empty($e->value)) { |
| 52 | $temp = new $class(); |
| 53 | $temp->value = '1'; |
| 54 | return $x->normalize($temp); |
| 55 | } |
| 56 | |
| 57 | return $x->normalize(static::slidingWindow($x, $e, $n, $class)); |
| 58 | } |
| 59 | |
| 60 | /** |
| 61 | * Modular reduction preparation |
| 62 | * |
| 63 | * @see self::slidingWindow() |
| 64 | */ |
| 65 | protected static function prepareReduce(string $x, string $n, string $class): string |
| 66 | { |
| 67 | return static::reduce($x, $n); |
| 68 | } |
| 69 | |
| 70 | /** |
| 71 | * Modular multiply |
| 72 | * |
| 73 | * @see self::slidingWindow() |
| 74 | */ |
| 75 | protected static function multiplyReduce(string $x, string $y, string $n, string $class): string |
| 76 | { |
| 77 | return static::reduce(bcmul($x, $y), $n); |
| 78 | } |
| 79 | |
| 80 | /** |
| 81 | * Modular square |
| 82 | * |
| 83 | * @see self::slidingWindow() |
| 84 | */ |
| 85 | protected static function squareReduce(string $x, string $n, string $class): string |
| 86 | { |
| 87 | return static::reduce(bcmul($x, $x), $n); |
| 88 | } |
| 89 | } |
| 90 |