I want to decrypt and enccrypt the data in flutter

Question

I want to encrypt the data in flutter using the AES cbc-128 algorithm. below is the java code for that i want to achieve the same functionality as below but in dart. i have tried

cryptography

dependency in flutter but the problem with that is that i want to use my own key in the algorithm as below in the java code. if you know any method for achieving this please let me know.

public static String Decrypt(String text, String key) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    byte[] keyBytes = new byte[16];
    byte[] b = key.getBytes("UTF-8");
    int len = b.length;
    if (len > keyBytes.length)
        len = keyBytes.length;
    System.arraycopy(b, 0, keyBytes, 0, len);
    SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
    IvParameterSpec ivSpec = new IvParameterSpec(keyBytes);
    cipher.init(Cipher.DECRYPT_MODE, keySpec, ivSpec);
    BASE64Decoder decoder = new BASE64Decoder();
    byte[] results = cipher.doFinal(decoder.decodeBuffer(text));
    return new String(results, "UTF-8");
}

public static String Encrypt(String text, String key) throws Exception {
    Cipher cipher = Cipher.getInstance("AES/CBC/PKCS5Padding");
    byte[] keyBytes = new byte[16];
    byte[] b = key.getBytes("UTF-8");
    int len = b.length;
    if (len > keyBytes.length)
        len = keyBytes.length;
    System.arraycopy(b, 0, keyBytes, 0, len);
    SecretKeySpec keySpec = new SecretKeySpec(keyBytes, "AES");
    IvParameterSpec ivSpec = new IvParameterSpec(keyBytes);
    cipher.init(Cipher.ENCRYPT_MODE, keySpec, ivSpec);
    byte[] results = cipher.doFinal(text.getBytes("UTF-8"));
    BASE64Encoder encoder = new BASE64Encoder();
    return encoder.encode(results);
}

Test Case

For the following input

plainText="This is plain text";

key="sahtojetrout2";

i want the encrypted result to be

encryptedText="8FmSMnDsFJVyNUXunhJLSmhFnRq89fl5DyTp0wdYfgk=";

which Topaco has written in an online editor you can check out that here Java Code. In flutter i have tried the program given at the Flutter site

Answer 1

You can do AES CBC-128 encryption in flutter with the help of crypt library. It supports the AES cbc encryption. The following sample code accepts key-string and plain-text as arguments and encrypts it as you have mentioned. You can pass your own key here. For AES-128, you need 128 bit key or 16 character string.

import 'package:encrypt/encrypt.dart';

void main() {
    final key = "Your16CharacterK";
    final plainText = "lorem ipsum example example";
    Encrypted encrypted = encrypt(key, plainText);
    String decryptedText = decrypt(key, encrypted);
    print(decryptedText);
}

String decrypt(String keyString, Encrypted encryptedData) {
    final key = Key.fromUtf8(keyString);
    final encrypter = Encrypter(AES(key, mode: AESMode.cbc));
    final initVector = IV.fromUtf8(keyString.substring(0, 16));
    return encrypter.decrypt(encryptedData, iv: initVector);
}

Encrypted encrypt(String keyString, String plainText) {
    final key = Key.fromUtf8(keyString);
    final encrypter = Encrypter(AES(key, mode: AESMode.cbc));
    final initVector = IV.fromUtf8(keyString.substring(0, 16));
    Encrypted encryptedData = encrypter.encrypt(plainText, iv: initVector);
    return encryptedData;
}

In the above example, the IV is created from the key itself to keep the code easy to read. Use random data for IV for better security. Referred article for flutter encryption.