SecretUtil.java

package com.xiaomai.geek.common.utils;

import android.text.TextUtils;
import android.util.Base64;

import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

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

/**
 * Created by XiaoMai on 2017/4/10 15:00.
 */

public class SecretUtil {

    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 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

    public static String md5(String string) {
        if (TextUtils.isEmpty(string)) {
            return "";
        }
        MessageDigest md5;
        try {
            md5 = MessageDigest.getInstance("MD5");
            byte[] bytes = md5.digest(string.getBytes());
            return parseByte2HexStr(bytes);
        } catch (NoSuchAlgorithmException e) {
            e.printStackTrace();
        }
        return "";
    }

    public static String encrypt(String content) {
        return encrypt("F9873622AF42269D252C789D7CDD5D7FD6912F40", content);
    }

    public static String decrypt(String content) {
        return decrypt("F9873622AF42269D252C789D7CDD5D7FD6912F40", content);
    }

    /*
    * 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;
    }

    //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));
    }

    /**
     * 将二进制转换成16进制
     * 
     * @param buf
     * @return
     */
    public static String parseByte2HexStr(byte buf[]) {
        StringBuffer sb = new StringBuffer();
        for (int i = 0; i < buf.length; i++) {
            String hex = Integer.toHexString(buf[i] & 0xFF);
            if (hex.length() == 1) {
                hex = '0' + hex;
            }
            sb.append(hex.toUpperCase());
        }
        return sb.toString();
    }

    // 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 >= 17) {
            sr = SecureRandom.getInstance(SHA1PRNG, "Crypto");
        } else {
            sr = SecureRandom.getInstance(SHA1PRNG);
        }
        // for Java
        // secureRandom = 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 (TextUtils.isEmpty(cleartext)) {
            return cleartext;
        }
        try {
            byte[] result = encrypt(key, cleartext.getBytes());
            return Base64.encodeToString(result, Base64.DEFAULT);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return null;
    }

    /*
     * 加密
     */
    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_PKCS5_PADDING);
        cipher.init(Cipher.ENCRYPT_MODE, skeySpec,
                new IvParameterSpec(new byte[cipher.getBlockSize()]));
        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 = Base64.decode(encrypted.getBytes(), Base64.DEFAULT);
            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_PKCS5_PADDING);
        cipher.init(Cipher.DECRYPT_MODE, skeySpec,
                new IvParameterSpec(new byte[cipher.getBlockSize()]));
        byte[] decrypted = cipher.doFinal(encrypted);
        return decrypted;
    }
}