Dart

AES Encrypt and Decrypt a File

_LANGUAGE_ demonstrates how to AES encrypt a file of any size, and then decrypt. 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.

  final crypt = CkCrypt2();

  crypt.cryptAlgorithm = 'aes';

  // CipherMode may be "ecb" or "cbc"
  crypt.cipherMode = 'cbc';

  // KeyLength may be 128, 192, 256
  crypt.keyLength = 256;

  // The padding scheme determines the contents of the bytes
  // that are added to pad the result to a multiple of the
  // encryption algorithm's block size.  AES has a block
  // size of 16 bytes, so encrypted output is always
  // a multiple of 16.
  crypt.paddingScheme = 0;

  // An initialization vector is required if using CBC mode.
  // ECB mode does not use an IV.
  // The length of the IV is equal to the algorithm's block size.
  // It is NOT equal to the length of the key.
  final ivHex = '000102030405060708090A0B0C0D0E0F';
  crypt.setEncodedIV(ivHex, 'hex');

  // The secret key must equal the size of the key.  For
  // 256-bit encryption, the binary secret key is 32 bytes.
  // For 128-bit encryption, the binary secret key is 16 bytes.
  final keyHex = '000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F';
  crypt.setEncodedKey(keyHex, 'hex');

  // Encrypt a file, producing the .aes as output.
  // The input file is unchanged, the output .aes contains the encrypted
  // contents of the input file.

  // Note: The .aes output file has no file format.  It is simply a stream
  // of bytes that resembles random binary data.
  var inFile = '/Users/chilkat/testData/pdf/sample.pdf';
  var outFile = '/Users/chilkat/testData/p7m/sample.pdf.aes';
  try {
    crypt.ckEncryptFile(inFile, outFile);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // For demonstration purposes, a different instance of the object will be used
  // for decryption.
  final decrypt = CkCrypt2();

  // All settings must match to be able to decrypt:
  decrypt.cryptAlgorithm = 'aes';
  decrypt.cipherMode = 'cbc';
  decrypt.keyLength = 256;
  decrypt.paddingScheme = 0;
  decrypt.setEncodedIV(ivHex, 'hex');
  decrypt.setEncodedKey(keyHex, 'hex');

  // Decrypt the .aes
  inFile = '/Users/chilkat/testData/p7m/sample.pdf.aes';
  outFile = '/Users/chilkat/testData/pdf/recovered.pdf';
  try {
    decrypt.ckDecryptFile(inFile, outFile);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Success!');
}