PHP

Duplicate PHP's openssl_encrypt and openssl_random_pseudo_bytes

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Demonstrates how to duplicate PHP's openssl_encrypt function. (https://www.php.net/manual/en/function.openssl-encrypt.php) Chilkat2 PHP

<?php

use Chilkat2\BinData;
use Chilkat2\Crypt2;

// This example requires the Chilkat API to have been previously unlocked.
// See Global Unlock Sample for sample code.

// Duplicates thw following PHP script:

// $text = "This is a test";
// $passphrase = "my password";
// $iv = openssl_random_pseudo_bytes(openssl_cipher_iv_length("AES-256-CBC"));
// $crypted = base64_encode($iv.openssl_encrypt($text, "AES-256-CBC", $passphrase, OPENSSL_RAW_DATA, $iv));
// echo $crypted;

$crypt = new Crypt2();

$text = 'This is a test';
$passphrase = 'my password';

// AES is a block cipher.  The IV size for any block cipher is the size of the block, which is defined by the encryption algorithm.
// For AES, the block size is always 16 bytes, regardless of key size (i.e. 128-bits, 192-bits, or 256-bits).
// Therefore, generate 16 random bytes for the IV.
$crypt->EncodingMode = 'base64';
$ivBase64 = $crypt->GenRandomBytesENC(16);

echo 'Generated IV = ', $ivBase64, "\n";

// Because we're doing AES-256-CBC, the key length must be 256-bits (i.e. 32 bytes).
// Given that our passphrase is a us-ascii string that can be shorter or longer than 32-bytes, we need to
// somehow transform the passphrase to a 32-byte secret key.  We need to know what openssl_encrypt does.
// Here's the answer from the openssl_encrypt documentation:
//
// "If the passphrase is shorter than expected, it is silently padded with NUL characters;
// if the passphrase is longer than expected, it is silently truncated."

// OK.... so let's pad or shorten to get a 32-byte key.
$bdKey = new BinData();
$bdKey->AppendString($passphrase, 'utf-8');

$sz = $bdKey->NumBytes;
if ($sz > 32) {
    $bdKey->RemoveChunk(32, $sz - 32);
} else {
    $bdKey->Clear();
    $bdKey->AppendPadded($passphrase, 'utf-8', false, 32);
}

// Setup for encryption.
$crypt->CryptAlgorithm = 'aes';
$crypt->KeyLength = 256;
$crypt->SetEncodedIV($ivBase64, 'base64');
$crypt->SetEncodedKey($bdKey->GetEncoded('base64'), 'base64');

// Encrypt and base64 encode.
$cipherText64 = $crypt->EncryptStringENC($text);

// The PHP code fragment above returns the base64 encoded bytes of the IV and the encrypted text.
// So let's do that..
$bd = new BinData();
$bd->AppendEncoded($ivBase64, 'base64');
$bd->AppendEncoded($cipherText64, 'base64');
$result = $bd->GetEncoded('base64');

echo 'result = ', $result, "\n";

// Sample output:
// dN0vS1O0cWi5BbLAAY+NTf7bs3S27xzPf11RkG47sjs=

// Now let's decrypt from the output...

// Setup for decryption.
$crypt->CryptAlgorithm = 'aes';
$crypt->KeyLength = 256;
$crypt->SetEncodedKey($bdKey->GetEncoded('base64'), 'base64');

$bdResult = new BinData();
$bdResult->AppendEncoded($result, 'base64');
$crypt->SetEncodedIV($bdResult->GetEncodedChunk(0, 16, 'base64'), 'base64');

// Remove the IV (first 16 bytes) from the result.
$bdResult->RemoveChunk(0, 16);
$crypt->DecryptBd($bdResult);
$originalText = $bdResult->GetString('utf-8');

echo 'original text = ', $originalText, "\n";