加密算法解析：MD5、DES和RAS的工作原理与特点

一、MD5不可逆加密

1.1-理解MD5

• MD5公开的算法，任何语言实现后其实都是一样的、通用的
• 不可逆加密：原文——加密——密文，密文无法解密出原文

1.2-MD5封装

using System.IO;
using System.Security.Cryptography;	

	/// <summary>
    /// 不可逆加密
    /// 1 防止被篡改
    /// 2 防止明文存储
    /// 3 防止抵赖，数字签名
    /// </summary>
    public class MD5Encrypt
    {
        #region MD5
        /// <summary>
        /// MD5加密,和动网上的16/32位MD5加密结果相同,
        /// 使用的UTF8编码
        /// </summary>
        /// <param name="source">待加密字串</param>
        /// <param name="length">16或32值之一,其它则采用.net默认MD5加密算法</param>
        /// <returns>加密后的字串</returns>
        public static string Encrypt(string source, int length = 32)//默认参数
        {
            if (string.IsNullOrEmpty(source)) return string.Empty;
            HashAlgorithm provider = CryptoConfig.CreateFromName("MD5") as HashAlgorithm;
            byte[] bytes = Encoding.UTF8.GetBytes(source);//这里需要区别编码的
            byte[] hashValue = provider.ComputeHash(bytes);
            StringBuilder sb = new StringBuilder();
            switch (length)
            {
                case 16://16位密文是32位密文的9到24位字符
                    for (int i = 4; i < 12; i++)
                    {
                        sb.Append(hashValue[i].ToString("x2"));
                    }
                    break;
                case 32:
                    for (int i = 0; i < 16; i++)
                    {
                        sb.Append(hashValue[i].ToString("x2"));
                    }
                    break;
                default:
                    for (int i = 0; i < hashValue.Length; i++)
                    {
                        sb.Append(hashValue[i].ToString("x2"));
                    }
                    break;
            }
            return sb.ToString();
        }
        #endregion MD5

        #region MD5摘要
        /// <summary>
        /// 获取文件的MD5摘要
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static string AbstractFile(string fileName)
        {
            using (FileStream file = new FileStream(fileName, FileMode.Open))
            {
                return AbstractFile(file);
            }
        }
        
        /// <summary>
        /// 根据stream获取文件摘要
        /// </summary>
        /// <param name="stream"></param>
        /// <returns></returns>
        public static string AbstractFile(Stream stream)
        {
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] retVal = md5.ComputeHash(stream);

            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < retVal.Length; i++)
            {
                sb.Append(retVal[i].ToString("x2"));
            }
            return sb.ToString();
        }
        #endregion
    }

1.3-MD5总结

• 相同原文加密的结果是一样的
• 不同长度的内容加密后都是32位，可以自行改变长度
• 原文件改动差别很小，结果差别很大
• 不管文件多大，都能产生32位长度的【摘要】，就是更具文件流进行加密的结果
  • 文件内容有一点改动，结果变化非常大
  • 文件内容不变，文件名变了，结果是不变的

1.4-MD5用途？

1. 防篡改
   1. 源代码管理器
   2. 急速秒传
      1. 在本地进行MD5摘要，到服务器上去检查，如果存在就不需要上传，直接在服务器上复制一份，或者指向路径跳转一下。
2. 密码保存：防止看到明文
   1. 密文是可见的，所以要求密码不能太检查；加盐（特殊字符+字母+数字）
   2. MD5是无法全部穷举出来的，无法全部解密出来的，像网上有很多这种；

3. 防止抵赖，数字签名
   1. 吧一些内容摘要一下，不能抵赖。

二、对称可逆加密DES

2.1-理解DES

• 对称可逆加密是公开的算法，任何语言实现后其实都一样，通用的。
• 加密后能解密会原文，但是需要一个Key
• 加密key和加密Key是同一个，也就是开门和锁门都要用同一吧钥匙
• 优点：加密解密的速度快
• 缺点：问题是秘钥的安全（key在网络中传输呗窃取），不是很安全

理解什么是对称可逆加密：

• 对称：加密/解密是key要一模一样的
• 可逆：原文加密到密文，密文解密到原文

2.2-DES封装

 	/// <summary>
    /// Des加密
    /// </summary>
    public class DesCrypto
    {

        //密钥
        private const string sKey = "qJzGEh6hESZDVJeCnFPGuxzaiB7NLQM3";
        //矢量，矢量可以为空
        private const string sIV = "qcDY6X+aPLw=";


        //构造一个对称算法
        private SymmetricAlgorithm mCSP = new TripleDESCryptoServiceProvider();

        /// <summary>
        /// 构造函数
        /// </summary>
        public DesCrypto() {
        
        }

        #region public string EncryptString(string Value)
        /// <summary>
        /// 加密字符串
        /// </summary>
        /// <param name="Value">输入的字符串</param>
        /// <returns>加密后的字符串</returns>
        public string EncryptString(string Value)
        {
            ICryptoTransform ct;
            MemoryStream ms;
            CryptoStream cs;
            byte[] byt;
            mCSP.Key = Convert.FromBase64String(sKey);
            mCSP.IV = Convert.FromBase64String(sIV);
            //指定加密的运算模式
            mCSP.Mode = System.Security.Cryptography.CipherMode.ECB;
            //获取或设置加密算法的填充模式
            mCSP.Padding = System.Security.Cryptography.PaddingMode.PKCS7;
            ct = mCSP.CreateEncryptor(mCSP.Key, mCSP.IV);
            byt = Encoding.UTF8.GetBytes(Value);
            ms = new MemoryStream();
            cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
            cs.Write(byt, 0, byt.Length);
            cs.FlushFinalBlock();
            cs.Close();
            return Convert.ToBase64String(ms.ToArray());
        }
        #endregion


        #region public string DecryptString(string Value)
        /// <summary>
        /// 解密字符串
        /// </summary>
        /// <param name="Value">加过密的字符串</param>
        /// <returns>解密后的字符串</returns>
        public string DecryptString(string Value)
        {
            ICryptoTransform ct;
            MemoryStream ms;
            CryptoStream cs;
            byte[] byt;
            mCSP.Key = Convert.FromBase64String(sKey);
            mCSP.IV = Convert.FromBase64String(sIV);
            mCSP.Mode = System.Security.Cryptography.CipherMode.ECB;
            mCSP.Padding = System.Security.Cryptography.PaddingMode.PKCS7;
            ct = mCSP.CreateDecryptor(mCSP.Key, mCSP.IV);
            byt = Convert.FromBase64String(Value);
            ms = new MemoryStream();
            cs = new CryptoStream(ms, ct, CryptoStreamMode.Write);
            cs.Write(byt, 0, byt.Length);
            cs.FlushFinalBlock();
            cs.Close();
            return Encoding.UTF8.GetString(ms.ToArray());
        }
        #endregion
    }

三、非对称可逆加密RSA

2.1-理解RSA

• 非对称可逆加密公开的算法，任何语言实现后其实都一样，通用的；
• 加密key和解密key不是一个，而是一对
• 加密key和解密key不能相互推到，有密文，没有解密key，也推导不出原文
• 缺点：速度不快
• 优点：安全性好

2.2-RSA封装

/// <summary>
    /// RSA加密解密及RSA签名和验证
    /// </summary>
    public class RsaEncrypt
    {

        public RsaEncrypt()
        {
        }

        #region RSA 的密钥产生
        /// <summary>
        /// RSA 的密钥产生 产生私钥 和公钥
        /// </summary>
        /// <param name="xmlKeys"></param>
        /// <param name="xmlPublicKey"></param>
        public void RSAKey(out string xmlKeys, out string xmlPublicKey)
        {
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            xmlKeys = rsa.ToXmlString(true);
            xmlPublicKey = rsa.ToXmlString(false);
        }
        #endregion


        #region RSA的加密函数
        //##############################################################################
        //RSA 方式加密
        //说明KEY必须是XML的行式,返回的是字符串
        //在有一点需要说明！！该加密方式有 长度 限制的！！
        //##############################################################################

        //RSA的加密函数  string
        public string RSAEncrypt(string xmlPublicKey, string m_strEncryptString)
        {

            byte[] PlainTextBArray;
            byte[] CypherTextBArray;
            string Result;
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPublicKey);
            PlainTextBArray = (new UnicodeEncoding()).GetBytes(m_strEncryptString);
            CypherTextBArray = rsa.Encrypt(PlainTextBArray, false);
            Result = Convert.ToBase64String(CypherTextBArray);
            return Result;

        }

        //RSA的加密函数 byte[]
        public string RSAEncrypt(string xmlPublicKey, byte[] EncryptString)
        {

            byte[] CypherTextBArray;
            string Result;
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPublicKey);
            CypherTextBArray = rsa.Encrypt(EncryptString, false);
            Result = Convert.ToBase64String(CypherTextBArray);
            return Result;
        }
        #endregion


        #region RSA的解密函数
        //RSA的解密函数  string
        public string RSADecrypt(string xmlPrivateKey, string m_strDecryptString)
        {
            byte[] PlainTextBArray;
            byte[] DypherTextBArray;
            string Result;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPrivateKey);
            PlainTextBArray = Convert.FromBase64String(m_strDecryptString);
            DypherTextBArray = rsa.Decrypt(PlainTextBArray, false);
            Result = (new UnicodeEncoding()).GetString(DypherTextBArray);
            return Result;
        }

        //RSA的解密函数  byte
        public string RSADecrypt(string xmlPrivateKey, byte[] DecryptString)
        {
            byte[] DypherTextBArray;
            string Result;
            System.Security.Cryptography.RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(xmlPrivateKey);
            DypherTextBArray = rsa.Decrypt(DecryptString, false);
            Result = (new UnicodeEncoding()).GetString(DypherTextBArray);
            return Result;

        }
        #endregion


        #region RSA数字签名
            #region 获取Hash描述表
            //获取Hash描述表 ，outofmemory.cn
            public bool GetHash(string m_strSource, ref byte[] HashData)
            {
                //从字符串中取得Hash描述
                byte[] Buffer;
                System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
                Buffer = System.Text.Encoding.GetEncoding("GB2312").GetBytes(m_strSource);
                HashData = MD5.ComputeHash(Buffer);

                return true;
            }

            //获取Hash描述表
            public bool GetHash(string m_strSource, ref string strHashData)
            {

                //从字符串中取得Hash描述
                byte[] Buffer;
                byte[] HashData;
                System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
                Buffer = System.Text.Encoding.GetEncoding("GB2312").GetBytes(m_strSource);
                HashData = MD5.ComputeHash(Buffer);

                strHashData = Convert.ToBase64String(HashData);
                return true;

            }

            //获取Hash描述表
            public bool GetHash(System.IO.FileStream objFile, ref byte[] HashData)
            {

                //从文件中取得Hash描述
                System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
                HashData = MD5.ComputeHash(objFile);
                objFile.Close();

                return true;

            }

            //获取Hash描述表
            public bool GetHash(System.IO.FileStream objFile, ref string strHashData)
            {

                //从文件中取得Hash描述
                byte[] HashData;
                System.Security.Cryptography.HashAlgorithm MD5 = System.Security.Cryptography.HashAlgorithm.Create("MD5");
                HashData = MD5.ComputeHash(objFile);
                objFile.Close();

                strHashData = Convert.ToBase64String(HashData);

                return true;

            }
            #endregion

            #region RSA签名
            //RSA签名
            public bool SignatureFormatter(string p_strKeyPrivate, byte[] HashbyteSignature, ref byte[] EncryptedSignatureData)
            {

                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPrivate);
                System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter(RSA);
                //设置签名的算法为MD5
                RSAFormatter.SetHashAlgorithm("MD5");
                //执行签名
                EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);

                return true;

            }

            //RSA签名
            public bool SignatureFormatter(string p_strKeyPrivate, byte[] HashbyteSignature, ref string m_strEncryptedSignatureData)
            {

                byte[] EncryptedSignatureData;

                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPrivate);
                System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter(RSA);
                //设置签名的算法为MD5
                RSAFormatter.SetHashAlgorithm("MD5");
                //执行签名
                EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);

                m_strEncryptedSignatureData = Convert.ToBase64String(EncryptedSignatureData);

                return true;

            }

            //RSA签名
            public bool SignatureFormatter(string p_strKeyPrivate, string m_strHashbyteSignature, ref byte[] EncryptedSignatureData)
            {

                byte[] HashbyteSignature;

                HashbyteSignature = Convert.FromBase64String(m_strHashbyteSignature);
                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPrivate);
                System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter(RSA);
                //设置签名的算法为MD5
                RSAFormatter.SetHashAlgorithm("MD5");
                //执行签名
                EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);

                return true;

            }

            //RSA签名
            public bool SignatureFormatter(string p_strKeyPrivate, string m_strHashbyteSignature, ref string m_strEncryptedSignatureData)
            {

                byte[] HashbyteSignature;
                byte[] EncryptedSignatureData;

                HashbyteSignature = Convert.FromBase64String(m_strHashbyteSignature);
                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPrivate);
                System.Security.Cryptography.RSAPKCS1SignatureFormatter RSAFormatter = new System.Security.Cryptography.RSAPKCS1SignatureFormatter(RSA);
                //设置签名的算法为MD5
                RSAFormatter.SetHashAlgorithm("MD5");
                //执行签名
                EncryptedSignatureData = RSAFormatter.CreateSignature(HashbyteSignature);

                m_strEncryptedSignatureData = Convert.ToBase64String(EncryptedSignatureData);

                return true;

            }
            #endregion

            #region RSA 签名验证
            public bool SignatureDeformatter(string p_strKeyPublic, byte[] HashbyteDeformatter, byte[] DeformatterData)
            {

                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPublic);
                System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
                //指定解密的时候HASH算法为MD5
                RSADeformatter.SetHashAlgorithm("MD5");

                if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
                {
                    return true;
                }
                else
                {
                    return false;
                }

            }

            public bool SignatureDeformatter(string p_strKeyPublic, string p_strHashbyteDeformatter, byte[] DeformatterData)
            {

                byte[] HashbyteDeformatter;

                HashbyteDeformatter = Convert.FromBase64String(p_strHashbyteDeformatter);

                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPublic);
                System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
                //指定解密的时候HASH算法为MD5
                RSADeformatter.SetHashAlgorithm("MD5");

                if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
                {
                    return true;
                }
                else
                {
                    return false;
                }

            }

            public bool SignatureDeformatter(string p_strKeyPublic, byte[] HashbyteDeformatter, string p_strDeformatterData)
            {

                byte[] DeformatterData;

                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPublic);
                System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
                //指定解密的时候HASH算法为MD5
                RSADeformatter.SetHashAlgorithm("MD5");

                DeformatterData = Convert.FromBase64String(p_strDeformatterData);

                if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
                {
                    return true;
                }
                else
                {
                    return false;
                }

            }

            public bool SignatureDeformatter(string p_strKeyPublic, string p_strHashbyteDeformatter, string p_strDeformatterData)
            {

                byte[] DeformatterData;
                byte[] HashbyteDeformatter;

                HashbyteDeformatter = Convert.FromBase64String(p_strHashbyteDeformatter);
                System.Security.Cryptography.RSACryptoServiceProvider RSA = new System.Security.Cryptography.RSACryptoServiceProvider();

                RSA.FromXmlString(p_strKeyPublic);
                System.Security.Cryptography.RSAPKCS1SignatureDeformatter RSADeformatter = new System.Security.Cryptography.RSAPKCS1SignatureDeformatter(RSA);
                //指定解密的时候HASH算法为MD5
                RSADeformatter.SetHashAlgorithm("MD5");

                DeformatterData = Convert.FromBase64String(p_strDeformatterData);

                if (RSADeformatter.VerifySignature(HashbyteDeformatter, DeformatterData))
                {
                    return true;
                }
                else
                {
                    return false;
                }

            }
            #endregion
        #endregion
    }

2.3-公钥/私钥

• 公钥：公开的Key
• 私钥：不公开的Key
• 公开加密Key——>保证数据的安全传递
• 公开解密Key——>保证数据的不可抵赖
• C#内置实现了公钥加密/私钥解密，如果想要用第三方的DLL-BounccyCastle

四、数字证书

2.1-CA证书

2.2-单边认证https

2.3-双边认证

原文链接：https://www.cnblogs.com/kimiliucn/p/17607330.html

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