用C# 写一个用于文本文件加密和解密的方法

以下是一个简单的C#文本文件加密和解密的方法，使用了AES加密算法：

using System;
using System.IO;
using System.Security.Cryptography;
using System.Text;

public static class FileEncryption
{
    private static readonly byte[] Salt = Encoding.ASCII.GetBytes("This is a salt phrase");

    public static void EncryptFile(string inputFile, string outputFile, string password)
    {
        byte[] passwordBytes = Encoding.UTF8.GetBytes(password);

        using (FileStream fsInput = new FileStream(inputFile, FileMode.Open, FileAccess.Read))
        {
            using (FileStream fsEncrypted = new FileStream(outputFile, FileMode.Create, FileAccess.Write))
            {
                using (Aes aes = Aes.Create())
                {
                    Rfc2898DeriveBytes keyDerivationFunction = new Rfc2898DeriveBytes(passwordBytes, Salt, 1000);
                    aes.Key = keyDerivationFunction.GetBytes(aes.KeySize / 8);
                    aes.IV = keyDerivationFunction.GetBytes(aes.BlockSize / 8);

                    fsEncrypted.Write(Salt, 0, Salt.Length);

                    using (CryptoStream cs = new CryptoStream(fsEncrypted, aes.CreateEncryptor(), CryptoStreamMode.Write))
                    {
                        byte[] buffer = new byte[8192];
                        int bytesRead;

                        while ((bytesRead = fsInput.Read(buffer, 0, buffer.Length)) > 0)
                        {
                            cs.Write(buffer, 0, bytesRead);
                        }
                    }
                }
            }
        }
    }

    public static void DecryptFile(string inputFile, string outputFile, string password)
    {
        byte[] passwordBytes = Encoding.UTF8.GetBytes(password);

        using (FileStream fsInput = new FileStream(inputFile, FileMode.Open, FileAccess.Read))
        {
            byte[] salt = new byte[Salt.Length];
            fsInput.Read(salt, 0, salt.Length);

            using (FileStream fsDecrypted = new FileStream(outputFile, FileMode.Create, FileAccess.Write))
            {
                using (Aes aes = Aes.Create())
                {
                    Rfc2898DeriveBytes keyDerivationFunction = new Rfc2898DeriveBytes(passwordBytes, salt, 1000);
                    aes.Key = keyDerivationFunction.GetBytes(aes.KeySize / 8);
                    aes.IV = keyDerivationFunction.GetBytes(aes.BlockSize / 8);

                    using (CryptoStream cs = new CryptoStream(fsInput, aes.CreateDecryptor(), CryptoStreamMode.Read))
                    {
                        byte[] buffer = new byte[8192];
                        int bytesRead;

                        while ((bytesRead = cs.Read(buffer, 0, buffer.Length)) > 0)
                        {
                            fsDecrypted.Write(buffer, 0, bytesRead);
                        }
                    }
                }
            }
        }
    }
}

使用示例：

string inputFile = @"C:\plaintext.txt";
string encryptedFile = @"C:\encrypted.dat";
string decryptedFile = @"C:\decrypted.txt";
string password = "MySecretPassword";

FileEncryption.EncryptFile(inputFile, encryptedFile, password);
FileEncryption.DecryptFile(encryptedFile, decryptedFile, password);

注意：这只是一个简单的示例，实际应用中需要更复杂的加密和解密方法来确保数据的安全。