C#中MD5加密及验证

MD5的加密处理应用还是比较多，由于破解难度很大，基本上大型网站或者软件商，密码加密一般采用这种方式居多。

而MD5可以用来获得32、 16、8等全部部分内容加密内容，也可以获取其加密后的哈希值。

/// 获得32位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_32(string input)
        {
            System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create();
            byte[] data = md5.ComputeHash(System.Text.Encoding.Default.GetBytes(input));
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < data.Length; i++)
            {
                sb.Append(data[i].ToString("x2"));
            }
            return sb.ToString();
        }

        ///
        /// 获得16位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_16(string input)
        {
            return GetMD5_32(input).Substring(8, 16);
        }
        ///
        /// 获得8位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_8(string input)
        {
            return GetMD5_32(input).Substring(8, 8);
        }
        ///
        /// 获得4位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_4(string input)
        {
            return GetMD5_32(input).Substring(8, 4);
        }

        public static string MD5EncryptHash(String input)
        {
            MD5 md5 = new MD5CryptoServiceProvider();
            //the GetBytes method returns byte array equavalent of a string
            byte[] res = md5.ComputeHash(Encoding.Default.GetBytes(input), 0, input.Length);
            char[] temp = new char[res.Length];
            //copy to a char array which can be passed to a String constructor
            Array.Copy(res, temp, res.Length);
            //return the result as a string
            return new String(temp);
        }

对文件添加MD5标签及验证
这种方式比较有趣，我也是最近才发现其中的奥妙，其实我们为了防止文件被修改，可以采用这种方式预先添加MD5码，然后在程序代码中进行验证，这样至少可以减少部分篡改的行为吧，因为只要文件有些少的修改，Md5码将会发生变化的，呵呵。

///
        /// 对给定文件路径的文件加上标签
        ///
        /// 要加密的文件的路径
        /// 标签的值
        public static bool AddMD5(string path)
        {
            bool IsNeed = true;

            if (CheckMD5(path)) //已进行MD5处理
                IsNeed = false;

            try
            {
                FileStream fsread = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
                byte[] md5File = new byte[fsread.Length];
                fsread.Read(md5File, 0, (int)fsread.Length); // 将文件流读取到Buffer中
                fsread.Close();

                if (IsNeed)
                {
                    string result = MD5Buffer(md5File, 0, md5File.Length); // 对Buffer中的字节内容算MD5
                    byte[] md5 = System.Text.Encoding.ASCII.GetBytes(result); // 将字符串转换成字节数组以便写人到文件中
                    FileStream fsWrite = new FileStream(path, FileMode.Open, FileAccess.ReadWrite);
                    fsWrite.Write(md5File, 0, md5File.Length); // 将文件，MD5值 重新写入到文件中。
                    fsWrite.Write(md5, 0, md5.Length);
                    fsWrite.Close();
                }
                else
                {
                    FileStream fsWrite = new FileStream(path, FileMode.Open, FileAccess.ReadWrite);
                    fsWrite.Write(md5File, 0, md5File.Length);
                    fsWrite.Close();
                }
            }
            catch
            {
                return false;
            }

            return true;
        }

        ///
        /// 对给定路径的文件进行验证
        ///
        ///
        /// 是否加了标签或是否标签值与内容值一致
        public static bool CheckMD5(string path)
        {
            try
            {
                FileStream get_file = new FileStream(path, FileMode.Open, FileAccess.Read, FileShare.Read);
                byte[] md5File = new byte[get_file.Length]; // 读入文件
                get_file.Read(md5File, 0, (int)get_file.Length);
                get_file.Close();

                string result = MD5Buffer(md5File, 0, md5File.Length - 32); // 对文件除最后32位以外的字节计算MD5，这个32是因为标签位为32位。
                string md5 = System.Text.Encoding.ASCII.GetString(md5File, md5File.Length - 32, 32); //读取文件最后32位，其中保存的就是MD5值
                return result == md5;
            }
            catch
            {
                return false;
            }
        }

        ///
        /// 计算文件的MD5值
        ///
        /// MD5签名文件字符数组
        /// 计算起始位置
        /// 计算终止位置
        /// 计算结果
        private static string MD5Buffer(byte[] MD5File, int index, int count)
        {
            System.Security.Cryptography.MD5CryptoServiceProvider get_md5 = new System.Security.Cryptography.MD5CryptoServiceProvider();
            byte[] hash_byte = get_md5.ComputeHash(MD5File, index, count);
            string result = System.BitConverter.ToString(hash_byte);

            result = result.Replace("-", "");
            return result;
        }
        #endregion

SHA256加密算法

/// SHA256函数
        ///
        /// 原始字符串
        /// SHA256结果(返回长度为44字节的字符串)
        public static string SHA256(string str)
        {
            byte[] SHA256Data = Encoding.UTF8.GetBytes(str);
            SHA256Managed Sha256 = new SHA256Managed();
            byte[] Result = Sha256.ComputeHash(SHA256Data);
            return Convert.ToBase64String(Result); //返回长度为44字节的字符串
        }

以下是应用在开发中的实例：

using System;
using System.Collections.Generic;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.Linq;
using System.Security.Cryptography;
using System.Text;

namespace MIS
{
    class Encrypt
    {

        //数据存入，直接将byte[]保存入binary字段
        public static int AccountRegister(string accountName, string password,string firstname,string position,string phone)
        {
            //string connstr = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
            string connstr = configxml.xmlconn.readxml();
            SqlConnection conn = new SqlConnection(connstr);
            string bytePassword = Encrypt.GetMD5_32(password);//使用32位MD5加密
            conn.Open();

            SqlCommand cmd = new SqlCommand("Account_Add", conn);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlParameter prmAccountName = cmd.Parameters.Add(new SqlParameter("@accountName", SqlDbType.NVarChar, 50));
            prmAccountName.Value = accountName;
            SqlParameter prmPassword = cmd.Parameters.Add(new SqlParameter("@password", SqlDbType.NVarChar, 50));
            prmPassword.Value = bytePassword;
            SqlParameter prmFirstName = cmd.Parameters.Add(new SqlParameter("@FirstName", SqlDbType.NVarChar, 50));
            prmFirstName.Value = firstname;
            SqlParameter prmPosition = cmd.Parameters.Add(new SqlParameter("@position", SqlDbType.NVarChar, 50));
            prmPosition.Value = position;
            SqlParameter prmPhone = cmd.Parameters.Add(new SqlParameter("@phone", SqlDbType.NVarChar, 50));
            prmPhone.Value = phone;
            int myInt = cmd.ExecuteNonQuery();
            cmd.Dispose();
            conn.Close();
            return myInt;
        }
        //更新账户信息
        public static int AccountUpdate(string accountName, string password)
        {
            string connstr = ConfigurationManager.ConnectionStrings["connstr"].ConnectionString;
            string bytePassword = Encrypt.GetMD5_32(password);
            SqlConnection conn = new SqlConnection(connstr);
            conn.Open();
            SqlCommand cmd = new SqlCommand("Account_Update", conn);
            cmd.CommandType = CommandType.StoredProcedure;
            SqlParameter prmAccountName = cmd.Parameters.Add(new SqlParameter("@accountName", SqlDbType.NVarChar, 50));
            prmAccountName.Value = accountName;
            SqlParameter prmPassword = cmd.Parameters.Add(new SqlParameter("@password", SqlDbType.NVarChar, 50));
            prmPassword.Value = bytePassword;
            int myInt = cmd.ExecuteNonQuery();
            cmd.Dispose();
            conn.Close();
            return myInt;
        }
        /// SHA256函数
        ///
        /// 原始字符串
        /// SHA256结果(返回长度为44字节的字符串)
        ///
        //哈系散列转换
        public static byte[] GetSaltedPassword(string password)
        {
            SHA1 sha1 = SHA1.Create();
            //应用System.Text空间下的Unicode.GetBytes方法获得byte.
            byte[] bytePassword = sha1.ComputeHash(Encoding.Unicode.GetBytes(password));
            return bytePassword;
        }
        public static string SHA256(string str)
        {
            byte[] SHA256Data = Encoding.UTF8.GetBytes(str);
            SHA256Managed Sha256 = new SHA256Managed();
            byte[] Result = Sha256.ComputeHash(SHA256Data);
            return Convert.ToBase64String(Result); //返回长度为44字节的字符串
        }
        /// 获得32位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_32(string input)
        {
            System.Security.Cryptography.MD5 md5 = System.Security.Cryptography.MD5.Create();
            byte[] data = md5.ComputeHash(System.Text.Encoding.Default.GetBytes(input));
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < data.Length; i++)
            {
                sb.Append(data[i].ToString("x2"));
            }
            return sb.ToString();
        }
        ///
        /// 获得16位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_16(string input)
        {
            return GetMD5_32(input).Substring(8, 16);
        }
        ///
        /// 获得8位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_8(string input)
        {
            return GetMD5_32(input).Substring(8, 8);
        }
        ///
        /// 获得4位的MD5加密
        ///
        ///
        ///
        public static string GetMD5_4(string input)
        {
            return GetMD5_32(input).Substring(8, 4);
        }

        public static string MD5EncryptHash(String input)
        {
            MD5 md5 = new MD5CryptoServiceProvider();
            //the GetBytes method returns byte array equavalent of a string
            byte[] res = md5.ComputeHash(Encoding.Default.GetBytes(input), 0, input.Length);
            char[] temp = new char[res.Length];
            //copy to a char array which can be passed to a String constructor
            Array.Copy(res, temp, res.Length);
            //return the result as a string
            return new String(temp);
        }
    }
}