Java加解密

1. 算法

1.1 AES

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.UnsupportedEncodingException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;

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

public final class Encrypt {

    private static final String ALGORITHM = "AES/CBC/PKCS5Padding";
    public static final String UTF_8 = "UTF-8";

    /**
     * 加密
     * 
     * @param by
     *            加密内容
     * @param ivStr
     *            加密iv，包括秘钥和盐值，中间用逗号分隔
     * @return 密文
     */
    public static byte[] encrypt(byte[] by, String ivStr) {

        try {
            String[] ivs = ivStr.split(",");
            SecretKeySpec skeySpec = getKey(ivs[0]); // 秘钥
            IvParameterSpec iv = new IvParameterSpec(ivs[1].getBytes(UTF_8)); // 盐值
            Cipher encryptCipher = Cipher.getInstance(ALGORITHM);
            encryptCipher.init(Cipher.ENCRYPT_MODE, skeySpec, iv);
            byte[] encrypted = encryptCipher.doFinal(by);
            return encrypted;
        } catch (Exception e) {
            System.out.println("encrypt exception: " + e);
        }
        return null;
    }

    /**
     * 解密
     * 
     * @param by
     *            密文
     * @param ivStr
     *            解密iv，包括秘钥和盐值，中间用逗号分隔
     * @return 明文
     */
    public static byte[] decrypt(byte[] by, String ivStr) {
        try {
            String[] ivs = ivStr.split(",");
            SecretKeySpec skeySpec = getKey(ivs[0]); // 秘钥
            IvParameterSpec iv = new IvParameterSpec(ivs[1].getBytes(UTF_8)); // 盐值
            Cipher decryptCipher = Cipher.getInstance(ALGORITHM);
            decryptCipher.init(Cipher.DECRYPT_MODE, skeySpec, iv);

            if (by != null) {
                byte[] original = decryptCipher.doFinal(by);
                return original;
            }
        } catch (Exception e) {
            System.out.println("decrypt exception: " + e);
        }
        return null;
    }

    private static SecretKeySpec getKey(String strKey) throws UnsupportedEncodingException {
        byte[] arrBTmp = strKey.getBytes(UTF_8);

        byte[] arrB = new byte[16];

        int length = arrBTmp.length < arrB.length ? arrBTmp.length : arrB.length;

        System.arraycopy(arrBTmp, 0, arrB, 0, length);

        SecretKeySpec skeySpec = new SecretKeySpec(arrB, "AES");

        return skeySpec;
    }

    /**
     * 将二进制转换成16进制
     *
     * @param buf
     *            byte
     * @return String
     */
    private 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();
    }

    /**
     * 生成指定位数的随机字符串
     *
     * @param count
     *            生成字符串位数为count*2
     * @return 安全随机字符串
     */
    public static String getRandom(int count) {
        SecureRandom random = null;
        try {
            random = SecureRandom.getInstance("SHA1PRNG");
        } catch (NoSuchAlgorithmException e) {
            System.out.println("getRandom exception: " + e);
        }
        byte[] salt = new byte[count];
        random.nextBytes(salt);
        return parseByte2HexStr(salt);
    }

    public static void main(String[] args) throws Exception {
        String ivKey = Encrypt.getRandom(16 / 2) + "," + Encrypt.getRandom(16 / 2);
        // 对文本加解密
        String content = "Hello world";
        byte[] secret = Encrypt.encrypt(content.getBytes(Encrypt.UTF_8), ivKey); // 加密
        System.out.println(new String(Encrypt.decrypt(secret, ivKey), Encrypt.UTF_8)); // 解密

        // 对文件加解密
        // (1) 打开文件流以字节方式读入，然后加密，最后写入文件
        // (2) 打开文件流以字节方式读入，然后解密，最后写入文件
        File src = new File("d:\abc.txt");
        BufferedInputStream bis = new BufferedInputStream(new FileInputStream(src));
        byte[] buf = new byte[(int) src.length()];
        bis.read(buf);
        bis.close();
        byte[] ds = Encrypt.encrypt(buf, ivKey); // 加密

        byte[] out = Encrypt.decrypt(ds, ivKey); // 解密
        File dst = new File("d:\cba.txt"); // 解密之后的文件
        BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(dst));
        bos.write(out);
        bos.close();
        System.out.println("test finished...");

    }

}