Dart

Duplicate PHP's openssl_encrypt and openssl_random_pseudo_bytes

See more OpenSSL Examples

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

import 'package:chilkat/chilkat.dart';

void main() {
  // 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;

  final crypt = CkCrypt2();

  final text = 'This is a test';
  final 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';
  final ivBase64 = crypt.genRandomBytesENC(16);

  print('Generated IV = $ivBase64');

  // 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.
  final bdKey = CkBinData();
  bdKey.appendString(passphrase, 'utf-8');

  final 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.
  final 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..
  final bd = CkBinData();
  bd.appendEncoded(ivBase64, 'base64');
  bd.appendEncoded(cipherText64, 'base64');
  final result = bd.getEncoded('base64');

  print('result = $result');

  // 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');

  final bdResult = CkBinData();
  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);
  final originalText = bdResult.getString('utf-8');

  print('original text = $originalText');
}