java文件加解密算法

时间：2010-09-25 来源：Jet J.J.Cheng

java文件加解密 package smart.jrsoft.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.security.MessageDigest;

import javax.crypto.Cipher;
import javax.crypto.SecretKey;
import javax.crypto.SecretKeyFactory;
import javax.crypto.spec.DESKeySpec;

public class EncryptUtil {
    /**
     * 用户MD5不可逆算法对密钥字符串进行加密
     *
     * @param inStr
     * @return
     */
    public static String encrypt(String inStr) {
        MessageDigest md = null;
        String out = null;

        try {
            md = MessageDigest.getInstance("MD5");
            byte[] digest = md.digest(inStr.getBytes());
            out = byte2hex(digest);
        } catch (Exception e) {
            e.printStackTrace();
        }
        return out;
    }

    private static String byte2hex(byte[] b) {
        String hs = "";
        String stmp = "";
        for (int n = 0; n < b.length; n++) {
            stmp = (java.lang.Integer.toHexString(b[n] & 0XFF));
            if (stmp.length() == 1) {
                hs = hs + "0" + stmp;
            } else {
                hs = hs + stmp;
            }
        }
        return hs.toUpperCase();
    }

    /**
     * 加密方法输入：要加密的文件，密钥字符串输出：对输入的文件加密后，保存到同一文件夹下增加了".jsmt"扩展名的文件中。
     */
    public static int encryptFile(String FileName, String sKey) {
        int Rtn = 0;
        try {
            // 因为密钥须为32位的字符串，故将用户传递的参数用encrypt方法进行处理；
            // （由0-F组成，共32个字符，我们将其拆解为2个16位的密码后进行二次加密运算）如：
            // AD67EA2F3BE6E5AD D368DFE03120B5DF

            sKey = encrypt(sKey);
            System.out.println(sKey);
            if (sKey.length() != 32) {
                Rtn = -1; // sKey is Wrong. //密码长度必须等于32！
                return Rtn;
            }
            byte[] bytK1 = getKeyByStr(sKey.substring(0, 16));
            byte[] bytK2 = getKeyByStr(sKey.substring(16, 32));

            File fileIn = new File(FileName);
            if (!fileIn.exists()) {
                Rtn = -2; // 需要加密的文件没有找到。
                return Rtn;
            }

            FileInputStream fis = new FileInputStream(fileIn);
            byte[] bytIn = new byte[(int) fileIn.length()];
            for (int i = 0; i < fileIn.length(); i++) {
                bytIn[i] = (byte) fis.read();
            }

            // 加密
            byte[] bytOut = encryptByDES(encryptByDES(bytIn, bytK1), bytK2);
            String fileOut = fileIn.getPath() + ".jsmt";
            FileOutputStream fos = new FileOutputStream(fileOut);
            for (int i = 0; i < bytOut.length; i++) {
                fos.write((int) bytOut[i]);
            }
            fos.close();
            return Rtn;
        } catch (Exception e) {
            Rtn = -3; // 其他原因导致的加密失败！
            return Rtn;
        }
    }

    /**
     * 解密函数输入：要解密的文件，密钥字符串输出：对制定的文件进行解密处理，保存到用户指定的文件中。（注：待解密的文件扩展名必须为：.jsmt）
     */
    public static int decryptFile(String CryptFileName, String sKey) {
        int Rtn = 0; // 默认的返回值为0,成功！
        try {
            // 因为密钥须为32位的字符串，故将用户传递的参数用encrypt方法进行处理；
            // （由0-F组成，共32个字符，我们将其拆解为2个16位的密码后进行二次解密运算）如：
            // AD67EA2F3BE6E5AD D368DFE03120B5DF

            sKey = encrypt(sKey);
            if (sKey.length() != 32) {
                Rtn = -1; // sKey is Wrong. //密码长度必须等于32！
                return Rtn;
            }

            String strPath = CryptFileName;
            if (!strPath.substring(strPath.length() - 5).toLowerCase().equals(
                    ".jsmt")) {
                Rtn = -2; // CryptFileName 扩展名必须为：.jsmt
                return Rtn;
            }

            // 用户指定要保存的文件
            strPath = strPath.substring(0, strPath.length() - 5);
            byte[] bytK1 = getKeyByStr(sKey.substring(0, 16));
            byte[] bytK2 = getKeyByStr(sKey.substring(16, 32));

            File fileIn = new File(CryptFileName);
            if (!fileIn.exists()) {
                Rtn = -3; // 需要解密的文件没有找到。
                return Rtn;
            }

            FileInputStream fis = new FileInputStream(fileIn);
            byte[] bytIn = new byte[(int) fileIn.length()];
            for (int i = 0; i < fileIn.length(); i++) {
                bytIn[i] = (byte) fis.read();
            }

            // 解密
            byte[] bytOut = decryptByDES(decryptByDES(bytIn, bytK2), bytK1);
            File fileOut = new File(strPath);
            fileOut.createNewFile();
            FileOutputStream fos = new FileOutputStream(fileOut);
            for (int i = 0; i < bytOut.length; i++) {
                fos.write((int) bytOut[i]);
            }
            fos.close();
            return Rtn; // 解密成功
        } catch (Exception e) {
            Rtn = -4; // 其他原因导致的解密失败！
            return Rtn;
        }
    }

    /**
     * 用DES方法加密输入的字节 bytKey需为8字节长，是加密的密码
     */
    private static byte[] encryptByDES(byte[] bytP, byte[] bytKey)
            throws Exception {
        DESKeySpec desKS = new DESKeySpec(bytKey);
        SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
        SecretKey sk = skf.generateSecret(desKS);
        Cipher cip = Cipher.getInstance("DES");
        cip.init(Cipher.ENCRYPT_MODE, sk);
        return cip.doFinal(bytP);
    }

    /**
     * 用DES方法解密输入的字节 bytKey需为8字节长，是解密的密码
     */
    private static byte[] decryptByDES(byte[] bytE, byte[] bytKey)
            throws Exception {
        DESKeySpec desKS = new DESKeySpec(bytKey);
        SecretKeyFactory skf = SecretKeyFactory.getInstance("DES");
        SecretKey sk = skf.generateSecret(desKS);
        Cipher cip = Cipher.getInstance("DES");
        cip.init(Cipher.DECRYPT_MODE, sk);
        return cip.doFinal(bytE);
    }

    /**
     * 输入密码的字符形式，返回字节数组形式。如输入字符串：AD67EA2F3BE6E5AD
     * 返回字节数组：{173,103,234,47,59,230,229,173}
     */
    private static byte[] getKeyByStr(String str) {
        byte[] bRet = new byte[str.length() / 2];
        for (int i = 0; i < str.length() / 2; i++) {
            Integer itg = new Integer(16 * getChrInt(str.charAt(2 * i))
                    + getChrInt(str.charAt(2 * i + 1)));
            bRet[i] = itg.byteValue();
        }
        return bRet;
    }

    /**
     * 计算一个16进制字符的10进制值输入：0-F
     */
    private static int getChrInt(char chr) {
        int iRet = 0;
        if (chr == "0".charAt(0))
            iRet = 0;
        if (chr == "1".charAt(0))
            iRet = 1;
        if (chr == "2".charAt(0))
            iRet = 2;
        if (chr == "3".charAt(0))
            iRet = 3;
        if (chr == "4".charAt(0))
            iRet = 4;
        if (chr == "5".charAt(0))
            iRet = 5;
        if (chr == "6".charAt(0))
            iRet = 6;
        if (chr == "7".charAt(0))
            iRet = 7;
        if (chr == "8".charAt(0))
            iRet = 8;
        if (chr == "9".charAt(0))
            iRet = 9;
        if (chr == "A".charAt(0))
            iRet = 10;
        if (chr == "B".charAt(0))
            iRet = 11;
        if (chr == "C".charAt(0))
            iRet = 12;
        if (chr == "D".charAt(0))
            iRet = 13;
        if (chr == "E".charAt(0))
            iRet = 14;
        if (chr == "F".charAt(0))
            iRet = 15;
        return iRet;
    }

    /**
     * 随机产生一个密钥字符串，给输入流进行加密
     *
     * @param is
     * @return
     */

    /*public static EncryptInfo encryptInputStream1(InputStream is) {
        try {
            EncryptInfo encryptInfo = new EncryptInfo(is.available());
            String sKey = RandomEncryptString.getEncryptKeyStr();
            System.out.println(sKey);
            if (sKey.length() != 32) {// 密钥必须是32位 encryptInfo = new
                                        // EncryptInfo(0);
                encryptInfo.setEncryptKye("密钥必须是32位");
                return encryptInfo;
            }
            encryptInfo.setEncryptKye(sKey);
            byte[] bytK1 = getKeyByStr(sKey.substring(0, 16));
            byte[] bytK2 = getKeyByStr(sKey.substring(16, 32));
            byte[] bytIn = new byte[is.available()];
            int c;
            int i = 0;
            while ((c = is.read()) != -1) {
                bytIn[i] = (byte) c;
            } // 加密
            encryptInfo
                    .setBytes(encryptByDES(encryptByDES(bytIn, bytK1), bytK2));
            return encryptInfo;
        } catch (Exception e) {
            return null;
        }
    }*/

    public static byte[] encryptInputStream(InputStream is) {
        try {
            String sKey = encrypt("jiuqi.com.cn");
            if (sKey.length() != 32) {// 密钥必须是32位
                return null;
            }
            byte[] bytK1 = getKeyByStr(sKey.substring(0, 16));
            byte[] bytK2 = getKeyByStr(sKey.substring(16, 32));
            byte[] bytIn = new byte[is.available()];
            int c;
            int i = 0;
            while ((c = is.read()) != -1) {
                bytIn[i] = (byte) c;
                i++;
            }
            byte[] bytes = encryptByDES(encryptByDES(bytIn, bytK1), bytK2);
            return bytes;
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 利用密钥对文件流进行解密
     *
     * @param is
     *            文件流
     * @return
     */
    public static byte[] decryptInputStream(InputStream is) {
        try {
            String encryptKey = encrypt("jiuqi.com.cn");
            byte[] bytK1 = getKeyByStr(encryptKey.substring(0, 16));
            byte[] bytK2 = getKeyByStr(encryptKey.substring(16, 32));
            byte[] bytes = new byte[is.available()];
            is.read(bytes);
            return decryptByDES(decryptByDES(bytes, bytK2), bytK1);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

}// class is over.