Java で実装された AES 暗号化アルゴリズムの完全な例

import javax.crypto.Cipher;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import android.util.Base64;
/**
 * @author vipin.cb , vipin.cb@experionglobal.com <br>
 *     Sep 27, 2013, 5:18:34 PM <br>
 *     Package:- <b>com.veebow.util</b> <br>
 *     Project:- <b>Veebow</b>
 *     <p>
 */
public class AESCrypt {
  private final Cipher cipher;
  private final SecretKeySpec key;
  private AlgorithmParameterSpec spec;
  public static final String SEED_16_CHARACTER = "U1MjU1M0FDOUZ.Qz";
  public AESCrypt() throws Exception {
    // hash password with SHA-256 and crop the output to 128-bit for key
    MessageDigest digest = MessageDigest.getInstance("SHA-256");
    digest.update(SEED_16_CHARACTER.getBytes("UTF-8"));
    byte[] keyBytes = new byte[32];
    System.arraycopy(digest.digest(), 0, keyBytes, 0, keyBytes.length);
    cipher = Cipher.getInstance("AES/CBC/PKCS7Padding");
    key = new SecretKeySpec(keyBytes, "AES");
    spec = getIV();
  }
  public AlgorithmParameterSpec getIV() {
    byte[] iv = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, };
    IvParameterSpec ivParameterSpec;
    ivParameterSpec = new IvParameterSpec(iv);
    return ivParameterSpec;
  }
  public String encrypt(String plainText) throws Exception {
    cipher.init(Cipher.ENCRYPT_MODE, key, spec);
    byte[] encrypted = cipher.doFinal(plainText.getBytes("UTF-8"));
    String encryptedText = new String(Base64.encode(encrypted,
        Base64.DEFAULT), "UTF-8");
    return encryptedText;
  }
  public String decrypt(String cryptedText) throws Exception {
    cipher.init(Cipher.DECRYPT_MODE, key, spec);
    byte[] bytes = Base64.decode(cryptedText, Base64.DEFAULT);
    byte[] decrypted = cipher.doFinal(bytes);
    String decryptedText = new String(decrypted, "UTF-8");
    return decryptedText;
  }
}