using
 System;

using
 System.Security.Cryptography;

using
 System.IO;

using
 System.Text;


namespace
 SqlResetPwd


{
    class Program
    {
        static void Main(string[] args)
        {
            while (true) 
            { 
                ConsoleKeyInfo i = Console.ReadKey(true);
                if (i.Key == ConsoleKey.Escape)
                {
                    break;
                }
                else 
                {
                    Console.Write(“IN FileName:“); string inFileName = Console.ReadLine();
                    Console.Write(“OUT FileName:“); string outFileName = Console.ReadLine();
                    Console.Write(“PassWord:“); string password = Console.ReadLine();
                    Console.Write(“Choice 0:Encrypt  other:Dcrypt:“); string Choice = Console.ReadLine();


                    // Create the password key
                    byte[] saltValueBytes = Encoding.ASCII.GetBytes(“This is my sa1t“);
                    Rfc2898DeriveBytes passwordKey = new Rfc2898DeriveBytes(password, saltValueBytes);

                    // Create the algorithm and specify the key and IV
                    RijndaelManaged alg = new RijndaelManaged();
                    alg.Key = passwordKey.GetBytes(alg.KeySize / 8);
                    alg.IV = passwordKey.GetBytes(alg.BlockSize / 8);


                    if (Choice == “0“)
                    {

                        encrypt#region encrypt
                        // Create the password key
                        try
                        {

                            // Read the unencrypted file into fileData
                            FileStream inFile = new FileStream(inFileName, FileMode.Open, FileAccess.Read);
                            byte[] fileData = new byte[inFile.Length];
                            inFile.Read(fileData, 0, (int)inFile.Length);

                            // Create the ICryptoTransform and CryptoStream object 
                            ICryptoTransform encryptor = alg.CreateEncryptor();
                            FileStream outFile = new FileStream(outFileName, FileMode.OpenOrCreate, FileAccess.Write);
                            CryptoStream encryptStream = new CryptoStream(outFile, encryptor, CryptoStreamMode.Write);

                            // Write the contents to the CryptoStream
                            encryptStream.Write(fileData, 0, fileData.Length);

                            // Close the file handles
                            encryptStream.Close();
                            inFile.Close();
                            outFile.Close();
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine(ex.Message);
                            Console.ReadLine();
                        }

                        #endregion
                    }
                    else
                    {
                        dencrypt#region dencrypt
                        try
                        {

                            // Read the encrypted file into fileData
                            ICryptoTransform decryptor = alg.CreateDecryptor();
                            FileStream inFile = new FileStream(inFileName, FileMode.Open, FileAccess.Read);
                            CryptoStream decryptStream = new CryptoStream(inFile, decryptor, CryptoStreamMode.Read);
                            byte[] fileData = new byte[inFile.Length];
                            decryptStream.Read(fileData, 0, (int)inFile.Length);
                            // Write the contents of the unencrypted file
                            FileStream outFile = new FileStream(outFileName, FileMode.OpenOrCreate, FileAccess.Write);
                            outFile.Write(fileData, 0, fileData.Length);
                            // Close the file handles
                            decryptStream.Close();
                            inFile.Close();
                            outFile.Close();
                        }
                        catch (Exception ex)
                        {
                            Console.WriteLine(ex.Message);
                            Console.ReadLine();
                        }

                        #endregion
                    }
                }
            }
        }
    }
}

从中不难看出对称加密解密的步骤:

选择要采用的加解密算法的类

创建相应的KEY,IV

创建要读出或写入的文件流

利用SymmetricAlgorithm.CreateEncryptor() CreateDecryptor()方法创建ICryptoTransform对象

利用ICryptoTransform对象和创建的文件流创建CryptoStream对象

写入或读出加解密的文件流