加密算法

转载 https://blog.csdn.net/chenze666/article/details/79730753

以一个60M的文件为测试样本，经过1000次的测试平均值，三种算法的表现为：

MD5算法运行1000次的平均时间为：226ms
SHA1算法运行1000次的平均时间为：308ms
SHA256算法运行1000次的平均时间为：473ms
安全性方面，显然SHA256（又称SHA2）的安全性最高，但是耗时要比其他两种多很多。MD5相对较容易碰撞，因此，SHA1应该是这三种中性能最好的一款加密算法。

JAVA实现：

import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.zip.CRC32;
 
public class FileSafeCode {
    /**
     * 计算大文件 md5获取getMD5(); SHA1获取getSha1() CRC32获取 getCRC32()
     */
    protected static char hexDigits[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e',
            'f' };
    public static MessageDigest messagedigest = null;
 
    
 
    /**
     * 对一个文件获取md5值
     * 
     * @return md5串
     * @throws NoSuchAlgorithmException
     */
    public static String getMD5(File file) throws IOException, NoSuchAlgorithmException {
 
        messagedigest = MessageDigest.getInstance("MD5");
        FileInputStream in = new FileInputStream(file);
        FileChannel ch = in.getChannel();
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
        messagedigest.update(byteBuffer);
        return bufferToHex(messagedigest.digest());
    }
 
    /**
     * // * @param target 字符串 求一个字符串的md5值 // * @return md5 value //
     */
    // public static String StringMD5(String target) {
    // return DigestUtils.md5Hex(target);
    // }
 
    /***
     * 计算SHA1码
     * 
     * @return String 适用于上G大的文件
     * @throws NoSuchAlgorithmException
     */
    public static String getSha1(File file) throws OutOfMemoryError, IOException, NoSuchAlgorithmException {
        messagedigest = MessageDigest.getInstance("SHA-1");
        FileInputStream in = new FileInputStream(file);
        FileChannel ch = in.getChannel();
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
        messagedigest.update(byteBuffer);
        return bufferToHex(messagedigest.digest());
    }
 
    /**
     * 获取文件SHA256码
     * 
     * @return String
     */
    public static String getSha256(File file) throws OutOfMemoryError, IOException, NoSuchAlgorithmException {
        messagedigest = MessageDigest.getInstance("SHA-256");
        FileInputStream in = new FileInputStream(file);
        FileChannel ch = in.getChannel();
        MappedByteBuffer byteBuffer = ch.map(FileChannel.MapMode.READ_ONLY, 0, file.length());
        messagedigest.update(byteBuffer);
        return bufferToHex(messagedigest.digest());
    }
 
    /**
     * 获取文件CRC32码
     * 
     * @return String
     */
    public static String getCRC32(File file) {
        CRC32 crc32 = new CRC32();
        // MessageDigest.get
        FileInputStream fileInputStream = null;
        try {
            fileInputStream = new FileInputStream(file);
            byte[] buffer = new byte[8192];
            int length;
            while ((length = fileInputStream.read(buffer)) != -1) {
                crc32.update(buffer, 0, length);
            }
            return crc32.getValue() + "";
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return null;
        } catch (IOException e) {
            e.printStackTrace();
            return null;
        } finally {
            try {
                if (fileInputStream != null)
                    fileInputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
 
    public static String getMD5String(String s) {
        return getMD5String(s.getBytes());
    }
 
    public static String getMD5String(byte[] bytes) {
        messagedigest.update(bytes);
        return bufferToHex(messagedigest.digest());
    }
 
    /**
     * @Description 计算二进制数据
     * @return String
     */
    private static String bufferToHex(byte bytes[]) {
        return bufferToHex(bytes, 0, bytes.length);
    }
 
    private static String bufferToHex(byte bytes[], int m, int n) {
        StringBuffer stringbuffer = new StringBuffer(2 * n);
        int k = m + n;
        for (int l = m; l < k; l++) {
            appendHexPair(bytes[l], stringbuffer);
        }
        return stringbuffer.toString();
    }
 
    private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
        char c0 = hexDigits[(bt & 0xf0) >> 4];
        char c1 = hexDigits[bt & 0xf];
        stringbuffer.append(c0);
        stringbuffer.append(c1);
    }
 
    public static boolean checkPassword(String password, String md5PwdStr) {
        String s = getMD5String(password);
        return s.equals(md5PwdStr);
    }
}