HackerRank之Java MD5

左手的ㄟ右手 2022-04-01 21:29 213阅读 0赞

*MD5* (*Message-Digest algorithm 5*) is a widely-used cryptographic hash function with a -bit hash value. Here are some common uses for *MD5*:

*  To store a one-way hash of a password.
 *  To provide some assurance that a transferred file has arrived intact.

*MD5* is one in a series of message digest algorithms designed by Professor Ronald Rivest of MIT (Rivest, 1994); however, the security of *MD5* has been severely compromised, most infamously by the Flame malware in 2012. The *CMU Software Engineering Institute* essentially considers *MD5* to be ["cryptographically broken and unsuitable for further use"][cryptographically broken and unsuitable for further use].

Given an alphanumeric string, , denoting a password, compute and print its *MD5* encryption value.

Answer

import java.io.*;
    import java.util.*;
    import java.security.MessageDigest;
    import java.security.NoSuchAlgorithmException;
    
    
    public class Solution {
    
        // 全局数组
        private final static String[] strDigits = { "0", "1", "2", "3", "4", "5",
                "6", "7", "8", "9", "a", "b", "c", "d", "e", "f" };
    
        public Solution() {
        }
    
        // 返回形式为数字跟字符串
        private static String byteToArrayString(byte bByte) {
            int iRet = bByte;
            // System.out.println("iRet="+iRet);
            if (iRet < 0) {
                iRet += 256;
            }
            int iD1 = iRet / 16;
            int iD2 = iRet % 16;
            return strDigits[iD1] + strDigits[iD2];
        }
    
        // 返回形式只为数字
        private static String byteToNum(byte bByte) {
            int iRet = bByte;
            System.out.println("iRet1=" + iRet);
            if (iRet < 0) {
                iRet += 256;
            }
            return String.valueOf(iRet);
        }
    
        // 转换字节数组为16进制字串
        private static String byteToString(byte[] bByte) {
            StringBuffer sBuffer = new StringBuffer();
            for (int i = 0; i < bByte.length; i++) {
                sBuffer.append(byteToArrayString(bByte[i]));
            }
            return sBuffer.toString();
        }
    
        public static String GetMD5Code(String strObj) {
            String resultString = null;
            try {
                resultString = new String(strObj);
                MessageDigest md = MessageDigest.getInstance("MD5");
                // md.digest() 该函数返回值为存放哈希值结果的byte数组
                resultString = byteToString(md.digest(strObj.getBytes()));
            } catch (NoSuchAlgorithmException ex) {
                ex.printStackTrace();
            }
            return resultString;
        }
    
        public static void main(String[] args) {
            Solution getMD5 = new Solution();
            Scanner scan=new Scanner(System.in);
            String str=scan.nextLine();
            scan.close();
            System.out.println(getMD5.GetMD5Code(str));
        }
    }

[cryptographically broken and unsuitable for further use]: https://en.wikipedia.org/wiki/MD5