Thursday, 7 December 2017

Encryption Decryption Example Android Using AES Alogirthm







activity_main.xml
-------------------------
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context="android.anil.com.demoencryptiondecryption.MainActivity">


    <EditText
        android:id="@+id/editText_value"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="Enter any  value!"
        android:inputType="textPersonName" />

    <Button
        android:id="@+id/button_encryption"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Encrypt" />

    <TextView
        android:id="@+id/textView_disencry"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="" />

    <Button
        android:id="@+id/button_discryption"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="Decrypt" />

    <TextView
        android:id="@+id/textView_disde"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:text="" />
</LinearLayout>

AESHelper.Java
------------------
package android.anil.com.demoencryptiondecryption.utils;

import android.util.Base64;
import android.util.Log;

import java.io.UnsupportedEncodingException;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

/**
 * Created by Anil .
 */

public class AESHelper {

    private static final String TAG = "AESCrypt";

    //AESCrypt-ObjC uses CBC and PKCS7Padding
    private static final String AES_MODE = "AES/CBC/PKCS7Padding";
    private static final String CHARSET = "UTF-8";

    //AESCrypt-ObjC uses SHA-256 (and so a 256-bit key)
    private static final String HASH_ALGORITHM = "SHA-256";

    //AESCrypt-ObjC uses blank IV (not the best security, but the aim here is compatibility)
    private static final byte[] ivBytes = {0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

    //togglable log option (please turn off in live!)
    public static boolean DEBUG_LOG_ENABLED = false;


    /**
     * Generates SHA256 hash of the password which is used as key
     *
     * @param password used to generated key
     * @return SHA256 of the password
     */
    private static SecretKeySpec generateKey(final String password) throws NoSuchAlgorithmException, UnsupportedEncodingException {
        final MessageDigest digest = MessageDigest.getInstance(HASH_ALGORITHM);
        byte[] bytes = password.getBytes("UTF-8");
        digest.update(bytes, 0, bytes.length);
        byte[] key = digest.digest();

        log("SHA-256 key ", key);

        SecretKeySpec secretKeySpec = new SecretKeySpec(key, "AES");
        return secretKeySpec;
    }


    /**
     * Encrypt and encode message using 256-bit AES with key generated from password.
     *
     * @param password used to generated key
     * @param message  the thing you want to encrypt assumed String UTF-8
     * @return Base64 encoded CipherText
     * @throws GeneralSecurityException if problems occur during encryption
     */
    public static String encrypt(final String password, String message)
            throws GeneralSecurityException {

        try {
            final SecretKeySpec key = generateKey(password);

            log("message", message);

            byte[] cipherText = encrypt(key, ivBytes, message.getBytes(CHARSET));

            //NO_WRAP is important as was getting \n at the end
            String encoded = Base64.encodeToString(cipherText, Base64.NO_WRAP);
            log("Base64.NO_WRAP", encoded);
            return encoded;
        } catch (UnsupportedEncodingException e) {
            if (DEBUG_LOG_ENABLED)
                Log.e(TAG, "UnsupportedEncodingException ", e);
            throw new GeneralSecurityException(e);
        }
    }


    /**
     * More flexible AES encrypt that doesn't encode
     *
     * @param key     AES key typically 128, 192 or 256 bit
     * @param iv      Initiation Vector
     * @param message in bytes (assumed it's already been decoded)
     * @return Encrypted cipher text (not encoded)
     * @throws GeneralSecurityException if something goes wrong during encryption
     */
    public static byte[] encrypt(final SecretKeySpec key, final byte[] iv, final byte[] message)
            throws GeneralSecurityException {
        final Cipher cipher = Cipher.getInstance(AES_MODE);
        IvParameterSpec ivSpec = new IvParameterSpec(iv);
        cipher.init(Cipher.ENCRYPT_MODE, key, ivSpec);
        byte[] cipherText = cipher.doFinal(message);

        log("cipherText", cipherText);

        return cipherText;
    }


    /**
     * Decrypt and decode ciphertext using 256-bit AES with key generated from password
     *
     * @param password                used to generated key
     * @param base64EncodedCipherText the encrpyted message encoded with base64
     * @return message in Plain text (String UTF-8)
     * @throws GeneralSecurityException if there's an issue decrypting
     */
    public static String decrypt(final String password, String base64EncodedCipherText)
            throws GeneralSecurityException {

        try {
            final SecretKeySpec key = generateKey(password);

            log("base64EncodedCipherText", base64EncodedCipherText);
            byte[] decodedCipherText = Base64.decode(base64EncodedCipherText, Base64.NO_WRAP);
            log("decodedCipherText", decodedCipherText);

            byte[] decryptedBytes = decrypt(key, ivBytes, decodedCipherText);

            log("decryptedBytes", decryptedBytes);
            String message = new String(decryptedBytes, CHARSET);
            log("message", message);


            return message;
        } catch (UnsupportedEncodingException e) {
            if (DEBUG_LOG_ENABLED)
                Log.e(TAG, "UnsupportedEncodingException ", e);

            throw new GeneralSecurityException(e);
        }
    }


    /**
     * More flexible AES decrypt that doesn't encode
     *
     * @param key               AES key typically 128, 192 or 256 bit
     * @param iv                Initiation Vector
     * @param decodedCipherText in bytes (assumed it's already been decoded)
     * @return Decrypted message cipher text (not encoded)
     * @throws GeneralSecurityException if something goes wrong during encryption
     */
    public static byte[] decrypt(final SecretKeySpec key, final byte[] iv, final byte[] decodedCipherText)
            throws GeneralSecurityException {
        final Cipher cipher = Cipher.getInstance(AES_MODE);
        IvParameterSpec ivSpec = new IvParameterSpec(iv);
        cipher.init(Cipher.DECRYPT_MODE, key, ivSpec);
        byte[] decryptedBytes = cipher.doFinal(decodedCipherText);

        log("decryptedBytes", decryptedBytes);

        return decryptedBytes;
    }


    private static void log(String what, byte[] bytes) {
        if (DEBUG_LOG_ENABLED)
            Log.d(TAG, what + "[" + bytes.length + "] [" + bytesToHex(bytes) + "]");
    }

    private static void log(String what, String value) {
        if (DEBUG_LOG_ENABLED)
            Log.d(TAG, what + "[" + value.length() + "] [" + value + "]");
    }


    /**
     * Converts byte array to hexidecimal useful for logging and fault finding
     *
     * @param bytes
     * @return
     */
    private static String bytesToHex(byte[] bytes) {
        final char[] hexArray = {'0', '1', '2', '3', '4', '5', '6', '7', '8',
                '9', 'A', 'B', 'C', 'D', 'E', 'F'};
        char[] hexChars = new char[bytes.length * 2];
        int v;
        for (int j = 0; j < bytes.length; j++) {
            v = bytes[j] & 0xFF;
            hexChars[j * 2] = hexArray[v >>> 4];
            hexChars[j * 2 + 1] = hexArray[v & 0x0F];
        }
        return new String(hexChars);
    }


}


MainActivity.Java
-----------------------------

package android.anil.com.demoencryptiondecryption;

import android.anil.com.demoencryptiondecryption.utils.AESHelper;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {
    EditText editTextValue;
    Button encryptButton, decryptButton;
    TextView disEncrypt, disDiscry;
    String enValue;
    String encryptedString;
    String KEY = "ABCDEFGHIJKLMNOPQRSWXYZ0123456789";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        encryptButton = findViewById(R.id.button_encryption);
        editTextValue = findViewById(R.id.editText_value);
        disEncrypt = findViewById(R.id.textView_disencry);
        disDiscry = findViewById(R.id.textView_disde);
        decryptButton = findViewById(R.id.button_discryption);
        encryptButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                enValue = editTextValue.getText().toString();
                if (enValue != null && !enValue.isEmpty()) {

                    encryptedString = encryption(enValue);
                    disEncrypt.setText(encryptedString);

                } else {
                    Toast.makeText(MainActivity.this, "Please Enter value", Toast.LENGTH_SHORT).show();
                }

            }
        });
        decryptButton.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                String decryptedString = decryption(encryptedString);
                disDiscry.setText(decryptedString);

            }
        });
    }

    public String encryption(String strNormalText) {
        String normalTextEnc = "";
        try {
            normalTextEnc = AESHelper.encrypt(KEY, strNormalText);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return normalTextEnc;
    }

    public String decryption(String strEncryptedText) {
        String strDecryptedText = "";
        try {
            strDecryptedText = AESHelper.decrypt(KEY, strEncryptedText);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return strDecryptedText;
    }
}





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