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。