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<?php |
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/* |
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* This file is part of the DUKPT package. |
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* |
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* Copyright (c) 2016-2017 Tonic Health <[email protected]> |
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* |
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* For the full copyright and license information, please view the LICENSE |
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* file that was distributed with this source code. |
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*/ |
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namespace TonicForHealth\DUKPT\Key; |
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use TonicForHealth\DUKPT\Helper\Encryption\DESEncryptionHelper; |
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/** |
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* Class DerivedKeyFactory |
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* |
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* @author Vitalii Ekert <[email protected]> |
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*/ |
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class DerivedKeyFactory implements KeyFactoryInterface |
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{ |
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const MODIFIED_KSN_SIZE_BYTES = 8; |
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const ENCRYPTION_KEY_SIZE_BYTES = 8; |
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/** |
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* @var DESEncryptionHelper |
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*/ |
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protected $encryptionHelper; |
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/** |
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* DerivedKeyFactory constructor. |
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* |
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* @param DESEncryptionHelper $encryptionHelper |
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*/ |
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public function __construct(DESEncryptionHelper $encryptionHelper) |
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{ |
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$this->encryptionHelper = $encryptionHelper; |
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} |
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/** |
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* {@inheritdoc} |
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* |
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* @return DerivedKey |
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*/ |
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public function createFromHexadecimal($hexKey) |
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{ |
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return new DerivedKey(hex2bin($hexKey)); |
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} |
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/** |
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* Returns a key from KSN and IPEK |
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* |
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* @param KeySerialNumber $ksn |
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* @param InitialPinEncryptionKey $ipek |
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* |
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* @throws \InvalidArgumentException If the provided key has a wrong size |
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* |
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* @return DerivedKey |
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*/ |
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public function create(KeySerialNumber $ksn, InitialPinEncryptionKey $ipek) |
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{ |
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$binKey = $ipek->toBinary(); |
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$binInitKSN = $ksn->getInitialKey(); |
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$binModifiedKSN = substr($binInitKSN, -self::MODIFIED_KSN_SIZE_BYTES); |
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$counter = hexdec(bin2hex($ksn->getEncryptionCounter())); |
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for ($mask = 0x100000; $mask > 0; $mask >>= 1) { |
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if (0 < ($value = $counter & $mask)) { |
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$hexValue = str_pad(dechex($value), DerivedKey::KEY_SIZE_BYTES, '0', STR_PAD_LEFT); |
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$binModifiedKSN |= hex2bin($hexValue); |
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$binKey = $this->calculateKey($binKey, $binModifiedKSN); |
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} |
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} |
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return new DerivedKey($binKey); |
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} |
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/** |
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* @param string $binCurrentSK |
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* @param string $binModifiedKSN |
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* |
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* @return string |
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*/ |
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protected function calculateKey($binCurrentSK, $binModifiedKSN) |
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{ |
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$binEncLowerMask = hex2bin(InitialPinEncryptionKeyFactory::ENCRYPTION_LOWER_KEY_MASK); |
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$binUpperBytes = $this->calculateKeyPart($binCurrentSK ^ $binEncLowerMask, $binModifiedKSN); |
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$binLowerBytes = $this->calculateKeyPart($binCurrentSK, $binModifiedKSN); |
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return $binUpperBytes.$binLowerBytes; |
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} |
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/** |
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* @param string $binCurrentSK |
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* @param string $binModifiedKSN |
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* |
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* @return string |
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*/ |
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protected function calculateKeyPart($binCurrentSK, $binModifiedKSN) |
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{ |
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$binUpperKey = substr($binCurrentSK, 0, self::ENCRYPTION_KEY_SIZE_BYTES); |
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$binLowerKey = substr($binCurrentSK, -self::ENCRYPTION_KEY_SIZE_BYTES); |
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$binMessage = $binLowerKey ^ $binModifiedKSN; |
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$cryptText = $this->encryptionHelper->encrypt($binUpperKey, $binMessage); |
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return $cryptText ^ $binLowerKey; |
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} |
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} |
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tonicforhealth /
dukpt
