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<?php
namespace Aws\Crypto\Cipher;
use Aws\Exception\CryptoException;
trait CipherBuilderTrait
{
/**
* Returns an identifier recognizable by `openssl_*` functions, such as
* `aes-256-cbc` or `aes-128-ctr`.
*
* @param string $cipherName Name of the cipher being used for encrypting
* or decrypting.
* @param int $keySize Size of the encryption key, in bits, that will be
* used.
*
* @return string
*/
protected function getCipherOpenSslName($cipherName, $keySize)
{
return "aes-{$keySize}-{$cipherName}";
}
/**
* Constructs a CipherMethod for the given name, initialized with the other
* data passed for use in encrypting or decrypting.
*
* @param string $cipherName Name of the cipher to generate for encrypting.
* @param string $iv Base Initialization Vector for the cipher.
* @param int $keySize Size of the encryption key, in bits, that will be
* used.
*
* @return CipherMethod
*
* @internal
*/
protected function buildCipherMethod($cipherName, $iv, $keySize)
{
switch ($cipherName) {
case 'cbc':
return new Cbc(
$iv,
$keySize
);
default:
return null;
}
}
/**
* Performs a reverse lookup to get the openssl_* cipher name from the
* AESName passed in from the MetadataEnvelope.
*
* @param $aesName
*
* @return string
*
* @internal
*/
protected function getCipherFromAesName($aesName)
{
switch ($aesName) {
case 'AES/GCM/NoPadding':
return 'gcm';
case 'AES/CBC/PKCS5Padding':
return 'cbc';
default:
throw new CryptoException('Unrecognized or unsupported'
. ' AESName for reverse lookup.');
}
}
}
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