RSA加密算法是一种非对称加密算法

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RSA加密算法是一种非对称加密算法。在公钥加密标准和电子商业中RSA被广泛使用。RSA是1977年由罗纳德•李维斯特（Ron Rivest）、阿迪•萨莫尔（Adi Shamir）和伦纳德•阿德曼（Leonard Adleman）一起提出的。当时他们三人都在麻省理工学院工作。RSA就是他们三人姓氏开头字母拼在一起组成的。.Net的推出，我们能够利用.Net Framework中的类提供的加密服务来保证数据安全。目前应用较为广泛的加密方法是使用RSA算法进行加密。在.Net Framework中与RSA加密算法相关的类主要有两个：RSA 类和RSACryptoServiceProvider 类。按照MSDN的说法RSA 类是“表示 RSA 算法的所有实现均从中继承的基类”，而RSACryptoServiceProvider 类是“使用加密服务提供程序 (CSP) 提供的 RSA 算法的实现执行不对称加密和解密”。另外，“表示 RSA 算法的标准参数”的RSAParameters 结构也是很重要的，它保存了RSA算法的参数。
这里具体讲述一下在C#中如何使用框架提供的RSA算法来对我们的信息加密、签名、验证签名、解密的这个几个步骤的实现

        using System.Security.Cryptography;        using System.Management;        using Microsoft.Win32;        /// <summary>        /// 生成公私钥        /// </summary>        /// <param name="PrivateKeyPath"></param>        /// <param name="PublicKeyPath"></param>        public void RSAKey(string PrivateKeyPath, string PublicKeyPath)        {            try            {                RSACryptoServiceProvider provider = new RSACryptoServiceProvider();                this.CreatePrivateKeyXML(PrivateKeyPath, provider.ToXmlString(true));                this.CreatePublicKeyXML(PublicKeyPath, provider.ToXmlString(false));            }            catch (Exception exception)            {                throw exception;            }        }        /// <summary>        /// 对原始数据进行MD5加密        /// </summary>        /// <param name="m_strSource">待加密数据</param>        /// <returns>返回机密后的数据</returns>        public string GetHash(string m_strSource)        {            HashAlgorithm algorithm = HashAlgorithm.Create("MD5");            byte[] bytes = Encoding.GetEncoding("GB2312").GetBytes(m_strSource);            byte[] inArray = algorithm.ComputeHash(bytes);            return Convert.ToBase64String(inArray);        }        /// <summary>        /// RSA加密        /// </summary>        /// <param name="xmlPublicKey">公钥</param>        /// <param name="m_strEncryptString">MD5加密后的数据</param>        /// <returns>RSA公钥加密后的数据</returns>        public string RSAEncrypt(string xmlPublicKey, string m_strEncryptString)        {            string str2;            try            {                RSACryptoServiceProvider provider = new RSACryptoServiceProvider();                provider.FromXmlString(xmlPublicKey);                byte[] bytes = new UnicodeEncoding().GetBytes(m_strEncryptString);                str2 = Convert.ToBase64String(provider.Encrypt(bytes, false));            }            catch (Exception exception)            {                throw exception;            }            return str2;        }        /// <summary>        /// RSA解密        /// </summary>        /// <param name="xmlPrivateKey">私钥</param>        /// <param name="m_strDecryptString">待解密的数据</param>        /// <returns>解密后的结果</returns>        public string RSADecrypt(string xmlPrivateKey, string m_strDecryptString)        {            string str2;            try            {                RSACryptoServiceProvider provider = new RSACryptoServiceProvider();                provider.FromXmlString(xmlPrivateKey);                byte[] rgb = Convert.FromBase64String(m_strDecryptString);                byte[] buffer2 = provider.Decrypt(rgb, false);                str2 = new UnicodeEncoding().GetString(buffer2);            }            catch (Exception exception)            {                throw exception;            }            return str2;        }        /// <summary>        /// 对MD5加密后的密文进行签名        /// </summary>        /// <param name="p_strKeyPrivate">私钥</param>        /// <param name="m_strHashbyteSignature">MD5加密后的密文</param>        /// <returns></returns>        public string SignatureFormatter(string p_strKeyPrivate, string m_strHashbyteSignature)        {            byte[] rgbHash = Convert.FromBase64String(m_strHashbyteSignature);            RSACryptoServiceProvider key = new RSACryptoServiceProvider();            key.FromXmlString(p_strKeyPrivate);            RSAPKCS1SignatureFormatter formatter = new RSAPKCS1SignatureFormatter(key);            formatter.SetHashAlgorithm("MD5");            byte[] inArray = formatter.CreateSignature(rgbHash);            return Convert.ToBase64String(inArray);        }        /// <summary>        /// 签名验证        /// </summary>        /// <param name="p_strKeyPublic">公钥</param>        /// <param name="p_strHashbyteDeformatter">待验证的用户名</param>        /// <param name="p_strDeformatterData">注册码</param>        /// <returns></returns>        public bool SignatureDeformatter(string p_strKeyPublic, string p_strHashbyteDeformatter, string p_strDeformatterData)        {            try            {                byte[] rgbHash = Convert.FromBase64String(p_strHashbyteDeformatter);                RSACryptoServiceProvider key = new RSACryptoServiceProvider();                key.FromXmlString(p_strKeyPublic);                RSAPKCS1SignatureDeformatter deformatter = new RSAPKCS1SignatureDeformatter(key);                deformatter.SetHashAlgorithm("MD5");                byte[] rgbSignature = Convert.FromBase64String(p_strDeformatterData);                if (deformatter.VerifySignature(rgbHash, rgbSignature))                {                    return true;                }                return false;            }            catch            {                return false;            }        }        /// <summary>        /// 获取硬盘ID        /// </summary>        /// <returns>硬盘ID</returns>        public string GetHardID()        {            string HDInfo = "";            ManagementClass cimobject1 = new ManagementClass("Win32_DiskDrive");            ManagementObjectCollection moc1 = cimobject1.GetInstances();            foreach (ManagementObject mo in moc1)            {                HDInfo = (string)mo.Properties["Model"].Value;            }            return HDInfo;        }        /// <summary>        /// 读注册表中指定键的值        /// </summary>        /// <param name="key">键名</param>        /// <returns>返回键值</returns>        private string ReadReg(string key)        {            string temp = "";            try            {                RegistryKey myKey = Registry.LocalMachine;                RegistryKey subKey = myKey.OpenSubKey(@"SOFTWARE/JX/Register");                 temp = subKey.GetValue(key).ToString();                subKey.Close();                myKey.Close();                return temp;            }            catch (Exception)            {                throw;//可能没有此注册项;            }         }         /// <summary>        /// 创建注册表中指定的键和值        /// </summary>        /// <param name="key">键名</param>        /// <param name="value">键值</param>        private void WriteReg(string key, string value)        {            try            {                RegistryKey rootKey = Registry.LocalMachine.CreateSubKey(@"SOFTWARE/JX/Register");                rootKey.SetValue(key, value);                rootKey.Close();            }            catch (Exception)            {                throw;            }        }        /// <summary>        /// 创建公钥文件        /// </summary>        /// <param name="path"></param>        /// <param name="publickey"></param>        public void CreatePublicKeyXML(string path, string publickey)        {            try            {                FileStream publickeyxml = new FileStream(path, FileMode.Create);                StreamWriter sw = new StreamWriter(publickeyxml);                sw.WriteLine(publickey);                sw.Close();                publickeyxml.Close();            }            catch            {                throw;            }        }        /// <summary>        /// 创建私钥文件        /// </summary>        /// <param name="path"></param>        /// <param name="privatekey"></param>        public void CreatePrivateKeyXML(string path, string privatekey)        {            try            {                FileStream privatekeyxml = new FileStream(path, FileMode.Create);                StreamWriter sw = new StreamWriter(privatekeyxml);                sw.WriteLine(privatekey);                sw.Close();                privatekeyxml.Close();            }            catch            {                throw;            }        }        /// <summary>        /// 读取公钥        /// </summary>        /// <param name="path"></param>        /// <returns></returns>        public string ReadPublicKey(string path)        {            StreamReader reader = new StreamReader(path);            string publickey = reader.ReadToEnd();            reader.Close();            return publickey;        }        /// <summary>        /// 读取私钥        /// </summary>        /// <param name="path"></param>        /// <returns></returns>        public string ReadPrivateKey(string path)        {            StreamReader reader = new StreamReader(path);            string privatekey = reader.ReadToEnd();            reader.Close();            return privatekey;        }        /// <summary>        /// 初始化注册表，程序运行时调用，在调用之前更新公钥xml        /// </summary>        /// <param name="path">公钥路径</param>        public void InitialReg(string path)        {            Registry.LocalMachine.CreateSubKey(@"SOFTWARE/JX/Register");            Random ra = new Random();            string publickey = this.ReadPublicKey(path);            if (Registry.LocalMachine.OpenSubKey(@"SOFTWARE/JX/Register").ValueCount <= 0)            {                this.WriteReg("RegisterRandom", ra.Next(1,100000).ToString());                this.WriteReg("RegisterPublicKey", publickey);            }            else            {                this.WriteReg("RegisterPublicKey", publickey);            }        }

如果是要对发送的消息进行加密和解密，加密时用公钥，解密时用私钥，即使密文被窃取也无法破解。

如果是要对软件进行注册，生成注册码，则服务端将用户的硬盘号用私钥加密，客户端用公钥解密，解密后将客户端的硬盘号进行MD5加密，将得到的结果和解密后的结果进行比较，如果相同，说明是注册用户，否则为非注册用户。