.NET中加密和解密---加密网络数据

    if (args.Length!=2)

    try
    {
    host = args[0];
    port = Int32.Parse(args[1]);
    }
    catch

    try //连接
    {
    client = new TcpClient();
    client.Connect(host,port);
    }
    catch(Exception e)

    try
    {
    Console.WriteLine("Connected. Sending public key.");
    rsa = new RSACryptoServiceProvider();
    rsa.KeySize = RSA_KEY_SIZE_BITS;
    sendPublicKey(rsa.ExportParameters(false),client);
    symm = new TripleDESCryptoServiceProvider();
    symm.KeySize = TDES_KEY_SIZE_BITS;

    MemoryStream ms = getRestOfMessage(client);
    extractSymmetricKeyInfo(rsa, symm, ms);
    showSecretMessage(symm, ms);
    }
    catch(Exception e)

    finally

    catch { //错误
    }
    }
    }

    private static void sendPublicKey(
    RSAParameters key,
    TcpClient client)
    {
    NetworkStream ns = client.GetStream();
    BinaryFormatter bf = new BinaryFormatter();
    bf.Serialize(ns,key);
    }

    private static MemoryStream getRestOfMessage(TcpClient client)
    {
    //获取加密的对称密钥、初始化矢量、秘密信息。对称密钥用公共RSA密钥
    //加密，秘密信息用对称密钥加密
    MemoryStream ms = new MemoryStream();
    NetworkStream ns = client.GetStream();
    byte[] buffer = new byte[1024];

    int len=0;

    // 将NetStream 的数据写入内存流
    while((len = ns.Read(buffer, 0, buffer.Length))>0)
    {
    ms.Write(buffer, 0, len);
    }
    ms.Position = 0;
    return ms;
    }

    private static void extractSymmetricKeyInfo(
    RSACryptoServiceProvider rsa,
    SymmetricAlgorithm symm,
    MemoryStream msOrig)
    {
    MemoryStream ms = new MemoryStream();

    // 获取TDES密钥--它被公共RSA密钥加密，使用私有密钥解密
    byte[] buffer = new byte[TDES_KEY_SIZE_BYTES];
    msOrig.Read(buffer,0,buffer.Length);
    symm.Key = rsa.Decrypt(buffer,false);

    // 获取TDES初始化矢量
    buffer = new byte[TDES_IV_SIZE_BYTES];
    msOrig.Read(buffer, 0, buffer.Length);
    symm.IV = rsa.Decrypt(buffer,false);
    }

    private static void showSecretMessage(
    SymmetricAlgorithm symm,
    MemoryStream msOrig)
    {
    //内存流中的所有数据都被加密了
    byte[] buffer = new byte[1024];
    int len = msOrig.Read(buffer,0,buffer.Length);

    MemoryStream ms = new MemoryStream();
    ICryptoTransform transform =
    symm.CreateDecryptor(symm.Key,symm.IV);
    CryptoStream cstream =new CryptoStream(ms, transform,
    CryptoStreamMode.Write);
    cstream.Write(buffer, 0, len);
    cstream.FlushFinalBlock();

    // 内存流现在是解密信息，是字节的形式，将它转换为字符串
    ms.Position = 0;
    len = ms.Read(buffer,0,(int) ms.Length);
    ms.Close();

    string msg = Encoding.ASCII.GetString(buffer,0,len);
    Console.WriteLine("The host sent me this secret message:");
    Console.WriteLine(msg);
    }
    }
    }