DES--可逆加密算法-密文可控

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package main;import java.security.Key;import java.security.NoSuchAlgorithmException;import java.security.SecureRandom;import javax.crypto.Cipher;import javax.crypto.KeyGenerator;public class CryptoUtil {    public static Key DEFAULT_KEY = null;    public static final String DEFAULT_ENCODE_RULES = CryptoUtil.class.getName();    public static final String DES = "DES";    public static void main(String[] args) {        String a = "20161021142843100001yagnpu123";        String key = DEFAULT_ENCODE_RULES + "yangpu1212";        System.out.println(a);        String strEnc = CryptoUtil.encode(key, a);// 加密字符串,返回String的密文        System.out.println(strEnc);        String strDes = CryptoUtil.decode(key, strEnc);// 把String 类型的密文解密        System.out.println(strDes);    }    static {        DEFAULT_KEY = obtainKey(DEFAULT_ENCODE_RULES);    }    /**     * 获得key     **/    public static Key obtainKey(String key) {        if (key == null) {            return DEFAULT_KEY;        }        KeyGenerator generator = null;        try {            generator = KeyGenerator.getInstance(DES);        } catch (NoSuchAlgorithmException e) {            e.printStackTrace();        }        generator.init(new SecureRandom(key.getBytes()));        Key key1 = generator.generateKey();        generator = null;        return key1;    }    /**     * 加密<br>     * String明文输入,String密文输出     */    public static String encode(String str) {        return encode(null, str);    }    /**     * 加密<br>     * String明文输入,String密文输出     */    public static String encode(String key, String str) {        return byteToString(obtainEncode(key, str.getBytes()));    }    /**     * 解密<br>     * 以String密文输入,String明文输出     */    public static String decode(String str) {        return decode(null, str);    }    /**     * 解密<br>     * 以String密文输入,String明文输出     */    public static String decode(String key, String str) {        return new String(obtainDecode(key, stringToByte(str)));    }    /**     * 加密<br>     * 以byte[]明文输入,byte[]密文输出     */    private static byte[] obtainEncode(String key, byte[] str) {        byte[] byteFina = null;        Cipher cipher;        try {            Key key1 = obtainKey(key);            cipher = Cipher.getInstance(DES);            cipher.init(Cipher.ENCRYPT_MODE, key1);            byteFina = cipher.doFinal(str);        } catch (Exception e) {            e.printStackTrace();        } finally {            cipher = null;        }        return byteFina;    }    /**     * 解密<br>     * 以byte[]密文输入,以byte[]明文输出     */    private static byte[] obtainDecode(String key, byte[] str) {        Cipher cipher;        byte[] byteFina = null;        try {            Key key1 = obtainKey(key);            cipher = Cipher.getInstance(DES);            cipher.init(Cipher.DECRYPT_MODE, key1);            byteFina = cipher.doFinal(str);        } catch (Exception e) {            e.printStackTrace();        } finally {            cipher = null;        }        return byteFina;    }    /**     * 将byte转换成string     */    public static String byteToString(byte[] b) {        // 转成16进制字符串        StringBuilder sb = new StringBuilder();        String stmp = "";        for (int n = 0; n < b.length; n++) {            // 整数转成十六进制表示            stmp = Integer.toHexString(b[n] & 0XFF);            if (stmp.length() == 1) {                sb.append("0" + stmp);            } else {                sb.append(stmp);            }        }        return sb.toString().toUpperCase(); // 转成大写    }    /**     * 将string转换成byte     */    public static byte[] stringToByte(String str) {        byte[] b = str.getBytes();        if ((b.length % 2) != 0)            throw new IllegalArgumentException(b + ":length is not even numbers");        byte[] b2 = new byte[b.length / 2];        for (int n = 0; n < b.length; n += 2) {            String item = new String(b, n, 2);            // 两位一组，表示一个字节,把这样表示的16进制字符串，还原成一个进制字节            b2[n / 2] = (byte) Integer.parseInt(item, 16);        }        return b2;    }}
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