Android How to - Encrypt and decrypt with AES algorithm

Question

We would like to know how to encrypt and decrypt with AES algorithm.
Answer

//from   ww  w. j a  va2s .co m
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

import javax.crypto.Cipher;
import javax.crypto.KeyGenerator;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;

import android.util.Base64;

public class Crypto {
  private static final String CIPHER_TRANSFORMATION = "AES/ECB/PKCS7Padding";
  private static final String CIPHER_ALGORITHM = "AES";

  private SecretKeySpec keySpec;
  private Cipher cipher;

  public Crypto(String passphrase) {
    byte[] key = getKey(passphrase);

    keySpec = new SecretKeySpec(key, CIPHER_ALGORITHM);

    try {
      cipher = Cipher.getInstance(CIPHER_TRANSFORMATION, "BC");
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  public byte[] encryptAsBase64(byte[] input) {
    return Base64.encode(encrypt(input), 0);
  }

  public byte[] encrypt(byte[] input) {
    try {
      cipher.init(Cipher.ENCRYPT_MODE, keySpec);

      return cipher.doFinal(input);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  public byte[] decryptAsBase64(byte[] input) {
    return decrypt(Base64.decode(input, 0));
  }

  public byte[] decrypt(byte[] input) {
    try {
      cipher.init(Cipher.DECRYPT_MODE, keySpec);

      return cipher.doFinal(input);
    } catch (Exception e) {
      throw new RuntimeException(e);
    }
  }

  private byte[] getKey(String passphrase) {
    try {
      KeyGenerator kgen = KeyGenerator.getInstance(CIPHER_ALGORITHM);
      SecureRandom sr = SecureRandom.getInstance("SHA1PRNG");
      
      sr.setSeed(passphrase.getBytes());
      kgen.init(128, sr);
      
      SecretKey skey = kgen.generateKey();
            return skey.getEncoded();
    } catch (NoSuchAlgorithmException e) {
      throw new RuntimeException(e);
    }
  }
}