C#实现MD5，DES，Rsa加密解密

MD5加密

        /// <summary>
        /// 字符串MD5加密
        /// </summary>
        /// <param name="source">来源</param>
        /// <param name="length">长度(默认是32位)</param>
        /// <returns></returns>
        public static string Encrypt(string source, int length = 32)
        {
            if (string.IsNullOrEmpty(source)) return string.Empty;
            HashAlgorithm provider = CryptoConfig.CreateFromName("MD5") as HashAlgorithm;
            //这里需要注意的是编码
            byte[] bytes = Encoding.UTF8.GetBytes(source);
            byte[] hashValue = provider.ComputeHash(bytes);
            StringBuilder sb = new StringBuilder();
            switch (length)
            {
                case 16:
                    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();
        }

        /// <summary>
        /// 根据stream加密文件--（获取文件摘要）
        /// </summary>
        /// <param name="stream"></param>
        /// <returns></returns>
        public static string EncryptFile(Stream stream)
        {
            MD5 md5 = new MD5CryptoServiceProvider();
            byte[] bytes = md5.ComputeHash(stream);
            StringBuilder sb = new StringBuilder();
            for (int i = 0; i < bytes.Length; i++)
            {
                sb.Append(bytes[i].ToString("x2"));
            }
            return sb.ToString();
        }

MD5加密的一些特点：

1.不可逆加密 ，加密后密文是无法j解密出原文的；
2. 加密的内容差别跟小但是加密出来的密文差别却很大；
3. 原文相同加密出来的密文是一样的
4. 文件的大小不同，加密后的密文长度都是length长度的;文件内容有所改变时，产生的密文结果是非常大的（文件名称的改变，不会影响密文改变）

MD5的几点用途：

1.密码的保存，防止明文泄露
由于密文是可见的，所以要求密码原文不能过于简单，或者加盐（加前缀/后缀/MD5两遍等）
2.做数字签名，防止抵赖
将内容加密，由比较权威的第三方去保障，从而证明这个文件就是你做的来，不能抵赖
3.防止篡改
将内容的密文，交给使用者，使用者他拿到文件后进行MD5校验，查看内容是否被篡改

DES的加密&&解密

		public static class Constant
   		{
        	public static string DesKey = "beizhuledexiaopangxie";
    	}
    	private static byte[] _rgbKey = ASCIIEncoding.ASCII.GetBytes(Constant.DesKey.Substring(0, 8));
        private static byte[] _rgbIV = ASCIIEncoding.ASCII.GetBytes(Constant.DesKey.Substring(0, 8));
     	/// <summary>
        /// DES加密
        /// </summary>
        /// <param name="scource">待加密的原文</param>
        /// <returns></returns>
        public static string Encrypt(string scource) 
        {
            DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
            using (MemoryStream memStream = new MemoryStream()) 
            {
                CryptoStream cryptoStream = new CryptoStream(memStream, provider.CreateEncryptor(_rgbKey, _rgbIV), CryptoStreamMode.Write);
                StreamWriter sw = new StreamWriter(cryptoStream);
                sw.Write(scource);
                sw.Flush();
                cryptoStream.FlushFinalBlock();
                memStream.Flush();
                return Convert.ToBase64String(memStream.GetBuffer(), 0, (int)memStream.Length);
            }
        }
        /// <summary>
        /// DES解密
        /// </summary>
        /// <param name="scource">待解密的密文</param>
        /// <returns></returns>
        public static string Decrypt(string scource)
        {
            DESCryptoServiceProvider provider = new DESCryptoServiceProvider();
            byte[] buffer = Convert.FromBase64String(scource);
            using (MemoryStream memStream = new MemoryStream())
            {
                CryptoStream cryptoStream = new CryptoStream(memStream, provider.CreateDecryptor(_rgbKey, _rgbIV), CryptoStreamMode.Write);
                StreamWriter sw = new StreamWriter(cryptoStream);
                cryptoStream.Write(buffer,0,buffer.Length);
                cryptoStream.FlushFinalBlock();
                return ASCIIEncoding.UTF8.GetString(memStream.ToArray());
            }

        }

DES加密的一些特点：

1.对称可逆加密：加密和解密的key是一个，加密后可以解密回原文；
2.加密速度相比较RSA加密速度快，但是密钥安全行不能保证

RSA的加密&&解密

		/// <summary>
        /// 获取加密解密KEY
        /// </summary>
        /// <returns></returns>
		public static KeyValuePair<string, string> KeyValuePair()
        {
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            var publicKey = rsa.ToXmlString(false);
            var privateKey = rsa.ToXmlString(true);
            return new KeyValuePair<string, string>(publicKey, privateKey);
        }

        /// <summary>
        /// RSA加密
        /// </summary>
        /// <param name="scource">来源</param>
        /// <param name="key">加密key</param>
        /// <returns></returns>
        public static string Encrypt(string scource, string key)
        {
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(key);
            UnicodeEncoding unicodeEncoding = new UnicodeEncoding();
            byte[] DataToEncrypt = unicodeEncoding.GetBytes(scource);
            byte[] resultBytes = rsa.Encrypt(DataToEncrypt, false);
            return Convert.ToBase64String(resultBytes);
        }
        /// <summary>
        /// RSA解密
        /// </summary>
        /// <param name="scource">来源</param>
        /// <param name="key">解密key</param>
        /// <returns></returns>
        public static string Decrypt(string scource, string key)
        {
            byte[] DataToEncrypt = Convert.FromBase64String(scource);
            RSACryptoServiceProvider rsa = new RSACryptoServiceProvider();
            rsa.FromXmlString(key);
            byte[] resultBytes = rsa.Decrypt(DataToEncrypt, false);
            UnicodeEncoding unicodeEncoding = new UnicodeEncoding();
            return unicodeEncoding.GetString(resultBytes);
        }

RSA加密的一些特点：

1.非对称可逆加密：加密和解密的key不是一个而是一对，加密后可以解密回原文；
2.加密速度相比较DES加密速度慢，但是密钥安全性好
3.加密密钥作为私钥 ，解密密钥作为公钥，能够保证不可抵赖（可以做数字签名）
4.解密密钥作为私钥，加密key作为公钥，能保证数据安全

使用方式

static void Main(string[] args)
        {
            #region MD5
            {
                string testMD5 = "被煮了的小螃蟹";
                Console.WriteLine("MD5加密:" + MD5Encrypt.Encrypty(testMD5));
                
            }
            #endregion

            #region DES
            {
                string desStr = "被煮了的小螃蟹";
                Console.WriteLine("DES--Encrypt加密:" + DesEncrypt.Encrypt(desStr));
                Console.WriteLine("DES--Decrypt解密:" + DesEncrypt.Decrypt(DesEncrypt.Encrypt(desStr)));
            }
            #endregion

            #region RSA
            {
                string desStr = "被煮了的小螃蟹";
                KeyValuePair<string, string> keyValuePair = RsaEncrypt.KeyValuePair();
                string str = RsaEncrypt.Encrypt(desStr, keyValuePair.Key);
                Console.WriteLine("RSA--Encrypt加密:" + str);
                Console.WriteLine("RSA--Decrypt解密:" + RsaEncrypt.Decrypt(str, keyValuePair.Value));
            }
            #endregion


            Console.ReadLine();
        }

验证结果