Dart

AES and CHACHA20 Encrypt/Decrypt Text

See more Encryption Examples

Demonstrates the use of the new EncryptSb and DecryptSb methods introduced in Chilkat v9.5.0.67 to encrypt/decrypt the contents of StringBuilder objects.

Note: This example requires Chilkat v9.5.0.67 or greater.

Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example assumes the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  // First build a string to be encrypted
  final sb = CkStringBuilder();
  var i = 1;
  while (i < 10) {
    sb.appendInt(i);
    sb.append(' the quick brown fox jumped over the lazy dog.\r\n');
    i++;
  }

  print(sb.getAsString());

  // The string to be encrypted looks like this:

  // 1 the quick brown fox jumped over the lazy dog.
  // 2 the quick brown fox jumped over the lazy dog.
  // 3 the quick brown fox jumped over the lazy dog.
  // 4 the quick brown fox jumped over the lazy dog.
  // 5 the quick brown fox jumped over the lazy dog.
  // 6 the quick brown fox jumped over the lazy dog.
  // ...

  final crypt = CkCrypt2();

  // Specify the encryption to be used.
  // First we'll do AES-128 CBC
  crypt.cryptAlgorithm = 'aes';
  crypt.cipherMode = 'cbc';
  crypt.keyLength = 128;

  final ivHex = '000102030405060708090A0B0C0D0E0F';
  crypt.setEncodedIV(ivHex, 'hex');

  final keyHex = '000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F';
  crypt.setEncodedKey(keyHex, 'hex');

  // When EncryptSb is called, the contents of the source (sb)
  // remains unmodified.  The encrypted bytes are written into bdEncrypted.
  // If bdEncrypted already contained data, it is replaced with the encrypted bytes.
  final bdEncrypted = CkBinData();
  try {
    crypt.encryptSb(sb, bdEncrypted);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Examine the encrypted bytes:
  print(bdEncrypted.getEncoded('base64_mime'));

  // Sample encrypted data:

  // 0DdNZ22ckMMJBiaKhAu3wUEfh16XW356NIUsDmNs/xwbHe/p1201OmpfzwXwKktkAefu2pckrBgC
  // df+1w8lRo+KAy5n5wlAgMGM/UrsVJsp0BmDPk1vaxKrmrGpSXOVCQs1n2+0atIs5YLiOG+Va3+Mi
  // EQNb4YK7bNMmvt0++irBxTiGnkx/RncfKwgkbBUpl2x7yV13MW6lapDT6Md0DKAMsTXFJYGeIdEf
  // g2uxDDQzI5gUOUHTMrXQ8paD/K76KKB9Jpp/kAM9z8g/d8KUmuphA7KI64d38xsgOmcITlbhlCQ2
  // PDkcU6RRzX0FUTUSMgQukhy0jkLZEjHX9poKJD+iJTOkcQUC3OqR9hKhSrvIgJN4lxdR71MheOoQ
  // 2wmvRdq+agTWWh333Vmb6J6yDV79aSpnqEDrA8Ks7Xzciol0gve91+JtVJlJKjWwEzWEU8GxF7Q8
  // eaWI70lsC5nTLGcbqgKu6gzkzHlHyHaE2FAQA/d5I2dvfsAYUQCza0Zdyw8mmTtHhlP2Tfxj1uPv
  // H4Q7BGuKnx3SWT2CnpbX4091w7KzLAztrbFBo/Tf9w8ZpgTK9k1ryfW9/xnk6rW6iQ==

  // Decrypt to restore back to the original:
  final sbOriginal = CkStringBuilder();
  try {
    crypt.decryptSb(bdEncrypted, sbOriginal);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Examine the original data:
  print(sbOriginal.getAsString());

  // ----------------------------------------------------------------------------------
  // To do chacha20 encryption, just change the settings:

  crypt.cryptAlgorithm = 'chacha20';
  crypt.keyLength = 256;
  // The initial count is the initial block counter for the chacha20 algorithm.
  // It can be any integer, but must be set to the same when decrypting.
  crypt.initialCount = 22;

  // EncryptSb completely replaces the contents of bdEncrypted.
  crypt.encryptSb(sb, bdEncrypted);

  // However.. DecryptSb appends the decrypted text to whatever may
  // have already existed within sbOriginal.
  crypt.decryptSb(bdEncrypted, sbOriginal);

  print('----');
  print('The original data should be here twice.  Once from the AES decrypt, and again from the chacha20 decrypt.');
  print(sbOriginal.getAsString());
  print('Success.');
}