[Android]AES加密解密的实现

import android.text.TextUtils;

import org.apache.commons.lang3.StringUtils;

import java.security.SecureRandom;

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


public class AesUtils {

    private final static String HEX = "0123456789ABCDEF";

    //private  static final String CBC_PKCS5_PADDING = "AES/CBC/PKCS5Padding";//AES是加密方式 CBC是工作模式 PKCS5Padding是填充模式
    private static final String CBC_PKCS7_PADDING = "AES/ECB/PKCS7Padding";

    private static final String AES = "AES";//AES 加密

    private static final String SHA1PRNG = "SHA1PRNG";//// SHA1PRNG 强随机种子算法, 要区别4.2以上版本的调用方法

    private final static int JELLY_BEAN_4_2 = 17;

    /*
     * 生成随机数，可以当做动态的密钥 加密和解密的密钥必须一致，不然将不能解密
     */
    public static String generateKey() {
        try {
            SecureRandom localSecureRandom = SecureRandom.getInstance(SHA1PRNG);
            byte[] bytes_key = new byte[20];
            localSecureRandom.nextBytes(bytes_key);
            String str_key = toHex(bytes_key);
            return str_key;
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    // 对密钥进行处理
    private static byte[] getRawKey(byte[] seed) throws Exception {
        KeyGenerator kgen = KeyGenerator.getInstance(AES);
        //for android
        SecureRandom sr = null;
        // 在4.2以上版本中，SecureRandom获取方式发生了改变
        if (android.os.Build.VERSION.SDK_INT >= JELLY_BEAN_4_2) {
            sr = SecureRandom.getInstance(SHA1PRNG, "Crypto");
        } else {
            sr = SecureRandom.getInstance(SHA1PRNG);
        }
        sr.setSeed(seed);
        kgen.init(128, sr); //256 bits or 128 bits,192bits
        //AES中128位密钥版本有10个加密循环，192比特密钥版本有12个加密循环，256比特密钥版本则有14个加密循环。
        SecretKey skey = kgen.generateKey();
        byte[] raw = skey.getEncoded();
        return raw;
    }

    /*
     * 加密
     */
    public static String encrypt(String key, String cleartext) {
        if (StringUtils.isEmpty(cleartext)) {
            return cleartext;
        }
        try {
            byte[] result = encrypt(key, cleartext.getBytes());
            return toHex(result);//Base64Encoder.encode(result);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /*
    * 真正的加密
　　 * @param key
　　 * 密钥
　　 * @param clear
　　 * 将要加密的内容
　　 * @return 已经加密的内容

 

    */
    private static byte[] encrypt(String key, byte[] clear) throws Exception {
        byte[] raw = getRawKey(key.getBytes());
        SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
        Cipher cipher = Cipher.getInstance(CBC_PKCS7_PADDING);
        //cipher.init(Cipher.ENCRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec);
        byte[] encrypted = cipher.doFinal(clear);
        return encrypted;
    }

    /*
     * 解密
     */
    public static String decrypt(String key, String encrypted) {
        if (TextUtils.isEmpty(encrypted)) {
            return encrypted;
        }
        try {
            //byte[] enc = Base64Decoder.decodeToBytes(encrypted);
            byte[] enc = toByte(encrypted);
            byte[] result = decrypt(key, enc);
            return new String(result);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /*
     * 解密
     */
    private static byte[] decrypt(String key, byte[] encrypted) throws Exception {
        byte[] raw = getRawKey(key.getBytes());
        SecretKeySpec skeySpec = new SecretKeySpec(raw, AES);
        Cipher cipher = Cipher.getInstance(CBC_PKCS7_PADDING);
        //ECB mode does not use an IV
        //cipher.init(Cipher.DECRYPT_MODE, skeySpec, new IvParameterSpec(new byte[cipher.getBlockSize()]));
        cipher.init(Cipher.DECRYPT_MODE, skeySpec);
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }

    //二进制转字符
    public static String toHex(byte[] buf) {
        if (buf == null) {
            return "";
        }
        StringBuffer result = new StringBuffer(2 * buf.length);
        for (int i = 0; i < buf.length; i++) {
            appendHex(result, buf[i]);
        }
        return result.toString();
    }

    private static void appendHex(StringBuffer sb, byte b) {
        sb.append(HEX.charAt((b >> 4) & 0x0f)).append(HEX.charAt(b & 0x0f));
    }

    public static byte[] toByte(String hexString) {
        int len = hexString.length() / 2;
        byte[] result = new byte[len];
        for (int i = 0; i < len; i++) {
            result[i] = Integer.valueOf(hexString.substring(2 * i, 2 * i + 2),
                    16).byteValue();
        }
        return result;
    }
}