Encrypt and decrypt text

Here is a simple example of encryption and decryption in Sketchware. Follow the steps below.

1. Create a new project in Sketchware.

2. In main.xml add a LinearV linear1 inside a ScrollV vscroll1. Inside this add an EditText edittext1, add two Buttons button1 and button2, and two TextViews textview1 and textview2.

3. Create a More Block extra, here use an add source directly block and put following codes.

}

javax.crypto.KeyGenerator keyGenerator;
javax.crypto.SecretKey secretKey;
byte[] secretKeyen;
String strSecretKey;
byte[] IV = new byte[16];
byte[] cipherText;

public static byte[] encrypt(byte[] plaintext, javax.crypto.SecretKey key, byte[] IV) throws Exception{
javax.crypto.Cipher cipher = javax.crypto.Cipher.getInstance("AES");
javax.crypto.spec.SecretKeySpec keySpec = new javax.crypto.spec.SecretKeySpec(key.getEncoded(), "AES");
javax.crypto.spec.IvParameterSpec ivSpec = new javax.crypto.spec.IvParameterSpec(IV);
cipher.init(javax.crypto.Cipher.ENCRYPT_MODE, keySpec, ivSpec);
byte[] cipherText = cipher.doFinal(plaintext);
return cipherText;
}

public static String decrypt(byte[] cipherText, javax.crypto.SecretKey key, byte[] IV){
try {
javax.crypto.Cipher cipher = javax.crypto.Cipher.getInstance("AES");
javax.crypto.spec.SecretKeySpec keySpec = new javax.crypto.spec.SecretKeySpec(key.getEncoded(), "AES");
javax.crypto.spec.IvParameterSpec ivSpec = new javax.crypto.spec.IvParameterSpec(IV);
cipher.init(javax.crypto.Cipher.DECRYPT_MODE, keySpec, ivSpec);
byte[] decryptedText = cipher.doFinal(cipherText);
return new String(decryptedText);
} catch (Exception e) {
e.printStackTrace();
}
return null;
}
{

4. In onCreate, make button2 and textview2 setVisible GONE.


5. In event button1 onClick, make button2 and textview2 setVisible VISIBLE, and then use add source directly block to put following codes.

try {
keyGenerator = javax.crypto.KeyGenerator.getInstance("AES");
keyGenerator.init(256);
secretKey = keyGenerator.generateKey();
secretKeyen=secretKey.getEncoded();
cipherText = encrypt(edittext1.getText().toString().getBytes(), secretKey, IV);
textview1.setText(android.util.Base64.encodeToString(cipherText, android.util.Base64.DEFAULT));
} catch ( java.security.NoSuchAlgorithmException e){
showMessage(e.toString());
} catch (Exception e){
showMessage(e.toString());
}

6. In event button2 onClick, use add source directly block to put following codes.
try {
javax.crypto.SecretKey originalSecretKey = new javax.crypto.spec.SecretKeySpec(secretKeyen, 0, secretKeyen.length, "AES");
String decryptedText = decrypt(cipherText, originalSecretKey, IV); textview2.setText(decryptedText);
} catch (Exception e) {
e.printStackTrace();
}

7. Save and run the project.

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