C# 加密文件夹 内部程序可以访问 外部输入密码才可以访问 代码

在C#中，我们可以使用`System.IO.Packaging`和`System.Security.Cryptography`库来创建加密的文件夹，只有通过正确的密码才能访问其中的内容。以下是一个基本示例，展示了如何使用AES（高级加密标准）对文件夹进行加密：

using System;
using System.IO;
using System.IO.Compression;
using System.IO.Packaging;
using System.Security.Cryptography;

public class EncryptedFolder {
    private string encryptionKey; // 密钥存储或生成

    public EncryptedFolder(string password) {
        if (string.IsNullOrEmpty(password)) throw new ArgumentException("Password cannot be null or empty.");
        this.encryptionKey = Convert.ToBase64String(BitConverter.GetBytes(GenerateKeyFromPassword(password)));
    }

    private byte[] GenerateKeyFromPassword(string password) {
        using var sha256 = SHA256.Create();
        return sha256.ComputeHash(Encoding.UTF8.GetBytes(password));
    }

    public void EncryptDirectory(string sourcePath, string destinationPath) {
        if (!Directory.Exists(sourcePath)) throw new DirectoryNotFoundException($"Source directory not found: {sourcePath}");

        // 创建一个新的PackagePart来承载加密内容
        PackageRelationship relationship = CreatePackageRelationship(sourcePath);
        PackagePart packagePart = AddEncryptedZipToPackage(destinationPath, relationship);

        // 将源目录复制到加密包内
        CopyDirectoryToPackage(packagePart, sourcePath);
    }

    private PackageRelationship CreatePackageRelationship(string sourcePath) {
        PackagePart part = PackageRelationship.CreatePart(PackagePartNames.RootPartName, typeof(PackageRelationship).GUID.ToString(), CompressionOption.None);
        PackageRelationship relationship = new PackageRelationship(part.Uri, "http://schemas.microsoft.com/pkg/rels/#" + part.Uri.LocalPath, RelationshipTypes.Resolves);
        part.Properties["Target"] = sourcePath;
        return relationship;
    }

    private PackagePart AddEncryptedZipToPackage(string destinationPath, PackageRelationship relationship) {
        Package package = Package.Open(destinationPath, FileMode.Create);
        package_relationships.Add(relationship);
        
        Uri partUri = new Uri("/" + PackagePartNames.EncryptedFolderPartName, UriKind.Relative);
        PackagePart encryptedPart = package.CreatePart(partUri, "application/vnd.ms-zip", CompressionOption.Optimal);
        encryptedPart.FeedbackStream = new CryptoStream(Stream.Null, GetAesCryptoServiceProvider().CreateEncryptor(), CryptoStreamMode.Write);
        return encryptedPart;
    }

    private void CopyDirectoryToPackage(PackagePart packagePart, string sourcePath) {
        ZipArchiveEntry zipEntry = new ZipArchiveEntry(Path.GetFileName(sourcePath), ZipArchiveEntryMode.Create);
        using (var entryStream = packagePart.GetStream()) {
            zipEntry.Open();
            File.Copy(sourcePath, entryStream, true);
        }
    }

    private Aes CreateAesCryptoServiceProvider() {
        // AES encryption provider
        var aes = Aes.Create();
        aes.KeySize = 256;
        aes.BlockSize = 128;
        return aes;
    }

    private ICryptoTransform GetAesCryptoServiceProvider() {
        return CreateAesCryptoServiceProvider().CreateEncryptor();
    }
}

// 使用示例
public static void Main(string[] args) {
    string sourceDir = @"C:\source\";
    string encryptedFolder = @"C:\encryptedfolder.zip";
    EncryptedFolder folderEncryption = new EncryptedFolder("your_password_here");
    folderEncryption.EncryptDirectory(sourceDir, encryptedFolder);
}

注意：这个示例创建的是一个ZIP格式的加密文件夹，实际应用可能需要结合Windows的封装技术（如`FileStream`包装`ICryptoTransform`）以提供更完整的保护。