如何通过 Windows 窗体访问和加密您的文件

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引言

本文的目的是演示如何构建一个 Windows Forms 应用程序，该应用程序通过使用 RijndaelManaged 类来加密文件。RijndaelManaged 是一个对称算法，它利用自动生成的密钥和初始化向量 (IV) 来加密和解密数据。加密涉及创建一个密码（一种算法），该算法以数据和生成的密钥作为输入。算法的行为将取决于密钥的长度。对称算法是指使用相同的密钥来解密和加密数据文件的算法。在本例中，我们将使用 RSACryptoServiceProvider ，这是一种非对称算法，用于加密和解密由 RijndaelManaged 加密的密钥。非对称算法最适合用于少量数据，例如密钥，因为非对称算法比对称算法具有更多的开销。对称算法在生成时开销较小。顾名思义，RijndaelManaged 类由 .NET Framework 用于托管代码；作为一种政府加密标准，该算法也称为高级加密标准 (AES)。RijndaelManaged 算法使用的密钥长度范围为 128 到 256 位，以 32 位为增量。IV 代表初始化向量 (Initialization Vector)：这是对称加密算法用于进一步混淆要加密的第一块数据的数据，从而使未经授权的解密更加困难。然后，IV 获取或设置对称算法的初始化向量。与 Key 属性一样，加密器和解密器都必须指定相同的值。Key 获取或设置对称算法的密钥对。加密后，必须存储此值并将其传输给解密器。解密期间，必须指定用于加密的相同密钥。下载的解决方案文件使用 Visual Studio 2010 构建，但后面部分提供的代码作为单个文件为命令行构建。

此过程的第一步是创建三个文件夹：c:\docs、c:\Encrypt 和 c:\Decrypt。写出一些文本文件并将它们放入 C:\docs 目录中。Forms 应用程序需要在窗体表面上拖放六个按钮、两个标签和两个 OpenFileDialog 控件。第一个标签（位于窗体顶部）的 AutoSize 属性应设置为 false。这将为您提供空间来放大字体和更改颜色。这是我们单击“Create Keys”按钮时出现文本输出的地方。因此，将第一个标签的文本属性留空。第二个标签的文本应显示：“Secure Your Files”。该标签的 AutoSize 属性也设置为 false。

单个文件中的源代码

注意 private 方法 Encrypt 和 Decrypt ，以及按钮控件的事件处理程序。Encrypt 按钮处理程序调用该模块的 private 方法，Decrypt 方法也一样。请注意，此应用程序中没有用户输入字段。我们使用 OpenFileDialog 控件来访问要加密的文件。

using System;
using System.IO;

using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Security.Cryptography;
using System.Text;
using System.Windows.Forms;

namespace Security
{
    public partial class Form1 : Form
    {        
        private System.Windows.Forms.Button buttonEncryptFile;
        private System.Windows.Forms.Button buttonDecryptFile;
        private System.Windows.Forms.Button buttonCreateAsmKeys;
        private System.Windows.Forms.Button buttonExportPublicKey;
        private System.Windows.Forms.Button buttonImportPublicKey;
        private System.Windows.Forms.Button buttonGetPrivateKey;
        private System.Windows.Forms.OpenFileDialog openFileDialog1;
        private System.Windows.Forms.OpenFileDialog openFileDialog2;
        private System.Windows.Forms.Label label1;
        private System.Windows.Forms.PictureBox pictureBox1;
        private System.Windows.Forms.Label label2;

        public Form1()
        {
            InitializeComponent();
        }

        CspParameters cspp = new CspParameters();
        RSACryptoServiceProvider rsa;

        // Path variables for source, encryption, and
        // decryption folders. Must end with a backslash.
        const string EncrFolder = @"c:\Encrypt\";
        const string DecrFolder = @"c:\Decrypt\";
        const string SrcFolder = @"c:\docs\";

        // Public key file
        const string PubKeyFile = @"c:\encrypt\rsaPublicKey.txt";

        // Key container name for
        // private/public key value pair.
        const string keyName = "Key01";

         private void InitializeComponent()
         {
            this.buttonEncryptFile = new System.Windows.Forms.Button();
            this.buttonDecryptFile = new System.Windows.Forms.Button();
            this.buttonCreateAsmKeys = new System.Windows.Forms.Button();
            this.buttonExportPublicKey = new System.Windows.Forms.Button();
            this.buttonImportPublicKey = new System.Windows.Forms.Button();
            this.buttonGetPrivateKey = new System.Windows.Forms.Button();
            this.openFileDialog1 = new System.Windows.Forms.OpenFileDialog();
            this.openFileDialog2 = new System.Windows.Forms.OpenFileDialog();
            this.label1 = new System.Windows.Forms.Label();
            this.pictureBox1 = new System.Windows.Forms.PictureBox();
            this.label2 = new System.Windows.Forms.Label();
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit();
            this.SuspendLayout();
            // 
            // buttonEncryptFile
            // 
            this.buttonEncryptFile.Location = new System.Drawing.Point(484, 44);
            this.buttonEncryptFile.Name = "buttonEncryptFile";
            this.buttonEncryptFile.Size = new System.Drawing.Size(125, 23);
            this.buttonEncryptFile.TabIndex = 0;
            this.buttonEncryptFile.Text = "Encrypt File";
            this.buttonEncryptFile.UseVisualStyleBackColor = true;
            this.buttonEncryptFile.Click += 
		new System.EventHandler(this.buttonEncryptFile_Click);
            // 
            // buttonDecryptFile
            // 
            this.buttonDecryptFile.Location = new System.Drawing.Point(484, 95);
            this.buttonDecryptFile.Name = "buttonDecryptFile";
            this.buttonDecryptFile.Size = new System.Drawing.Size(125, 23);
            this.buttonDecryptFile.TabIndex = 1;
            this.buttonDecryptFile.Text = "Decrypt File";
            this.buttonDecryptFile.UseVisualStyleBackColor = true;
            this.buttonDecryptFile.Click += 
		new System.EventHandler(this.buttonDecryptFile_Click);
            // 
            // buttonCreateAsmKeys
            // 
            this.buttonCreateAsmKeys.Location = new System.Drawing.Point(484, 145);
            this.buttonCreateAsmKeys.Name = "buttonCreateAsmKeys";
            this.buttonCreateAsmKeys.Size = new System.Drawing.Size(125, 23);
            this.buttonCreateAsmKeys.TabIndex = 2;
            this.buttonCreateAsmKeys.Text = "Create Keys";
            this.buttonCreateAsmKeys.UseVisualStyleBackColor = true;
            this.buttonCreateAsmKeys.Click += 
		new System.EventHandler(this.buttonCreateAsmKeys_Click);
            // 
            // buttonExportPublicKey
            // 
            this.buttonExportPublicKey.Location = new System.Drawing.Point(484, 207);
            this.buttonExportPublicKey.Name = "buttonExportPublicKey";
            this.buttonExportPublicKey.Size = new System.Drawing.Size(125, 23);
            this.buttonExportPublicKey.TabIndex = 3;
            this.buttonExportPublicKey.Text = "Export Public Key";
            this.buttonExportPublicKey.UseVisualStyleBackColor = true;
            this.buttonExportPublicKey.Click += 
		new System.EventHandler(this.buttonExportPublicKey_Click);
            // 
            // buttonImportPublicKey
            // 
            this.buttonImportPublicKey.Location = new System.Drawing.Point(484, 271);
            this.buttonImportPublicKey.Name = "buttonImportPublicKey";
            this.buttonImportPublicKey.Size = new System.Drawing.Size(125, 23);
            this.buttonImportPublicKey.TabIndex = 4;
            this.buttonImportPublicKey.Text = "Import Public Key";
            this.buttonImportPublicKey.UseVisualStyleBackColor = true;

            this.buttonImportPublicKey.Click  += 
		new System.EventHandler(this.buttonImportPublicKey_Click);
            // 
            // buttonGetPrivateKey
            // 
            this.buttonGetPrivateKey.Location = new System.Drawing.Point(484, 330);
            this.buttonGetPrivateKey.Name = "buttonGetPrivateKey";
            this.buttonGetPrivateKey.Size = new System.Drawing.Size(125, 23);
            this.buttonGetPrivateKey.TabIndex = 5;
            this.buttonGetPrivateKey.Text = "Get Private Key";
            this.buttonGetPrivateKey.UseVisualStyleBackColor = true;
            this.buttonGetPrivateKey.Click += 
		new System.EventHandler(this.buttonGetPrivateKey_Click);
            
            this.openFileDialog1.FileName = "openFileDialog1";
            this.openFileDialog2.FileName = "openFileDialog2";
            this.label1.BackColor = System.Drawing.Color.Red;
            this.label1.Font = new System.Drawing.Font
	   ("Times New Roman", 21.75F, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.label1.Location = new System.Drawing.Point(46, 23);
            this.label1.Name = "label1";
            this.label1.Size = new System.Drawing.Size(262, 44);
            this.label1.TabIndex = 6;
            this.pictureBox1.Location = new System.Drawing.Point(101, 135);
            this.pictureBox1.Name = "pictureBox1";
            this.pictureBox1.Size = new System.Drawing.Size(165, 205);
            this.pictureBox1.TabIndex = 7;
            this.pictureBox1.TabStop = false;
            this.label2.Font = new System.Drawing.Font
	   ("Times New Roman", 18F, System.Drawing.GraphicsUnit.Point, ((byte)(0)));
            this.label2.Location = new System.Drawing.Point(52, 95);
            this.label2.Name = "label2";
            this.label2.Size = new System.Drawing.Size(214, 37);
            this.label2.TabIndex = 8;
            this.label2.Text = "Secure Your Files";
            // 
            // Form1
            // 
            this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F);
            this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font;
            this.BackColor = System.Drawing.Color.Cyan;
            this.ClientSize = new System.Drawing.Size(631, 395);
            this.Controls.Add(this.label2);
            this.Controls.Add(this.pictureBox1);
            this.Controls.Add(this.label1);
            this.Controls.Add(this.buttonGetPrivateKey);
            this.Controls.Add(this.buttonImportPublicKey);
            this.Controls.Add(this.buttonExportPublicKey);
            this.Controls.Add(this.buttonCreateAsmKeys);
            this.Controls.Add(this.buttonDecryptFile);
            this.Controls.Add(this.buttonEncryptFile);
            this.Name = "Form1";
            this.Text = "Form1";
            ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit();
            this.ResumeLayout(false);
        }

           [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            Application.Run(new Form1());
        }

     private void buttonCreateAsmKeys_Click(object sender, EventArgs e)
        {
            cspp.KeyContainerName = keyName;
            rsa = new RSACryptoServiceProvider(cspp);
            rsa.PersistKeyInCsp = true;
            if (rsa.PublicOnly == true)
                label1.Text = "Key: " + cspp.KeyContainerName + " - Public Only";
            else
                label1.Text = "Key: " + cspp.KeyContainerName + " - Full Key Pair";
        }

        private void buttonEncryptFile_Click(object sender, EventArgs e)
        {
            if (rsa == null)
                MessageBox.Show("Key not set.");
            else
            {
                // Display a dialog box to select a file to encrypt.
                openFileDialog1.InitialDirectory = SrcFolder;
                if (openFileDialog1.ShowDialog() == DialogResult.OK)
                {
                    string fName = openFileDialog1.FileName;
                    if (fName != null)
                    {
                        FileInfo fInfo = new FileInfo(fName);
                        // Pass the file name without the path.
                        string name = fInfo.FullName;
                        EncryptFile(name);
                    }
                }
            }
        }

        private void EncryptFile(string inFile)
        {
            // Create instance of Rijndael for
            // symmetric encryption of the data.
            RijndaelManaged rjndl = new RijndaelManaged();
            rjndl.KeySize = 256;
            rjndl.BlockSize = 256;
            rjndl.Mode = CipherMode.CBC;
            ICryptoTransform transform = rjndl.CreateEncryptor();

            // Use RSACryptoServiceProvider to
            // encrypt the Rijndael key.
            // rsa is previously instantiated: 
            //    rsa = new RSACryptoServiceProvider(cspp);
            byte[] keyEncrypted = rsa.Encrypt(rjndl.Key, false);

            // Create byte arrays to contain
            // the length values of the key and IV.
            byte[] LenK = new byte[4];
            byte[] LenIV = new byte[4];

            int lKey = keyEncrypted.Length;
            LenK = BitConverter.GetBytes(lKey);
            int lIV = rjndl.IV.Length;
            LenIV = BitConverter.GetBytes(lIV);

            // Write the following to the FileStream
            // for the encrypted file (outFs):
            // - length of the key
            // - length of the IV
            // - encrypted key
            // - the IV
            // - the encrypted cipher content

            int startFileName = inFile.LastIndexOf("\\") + 1;
            // Change the file's extension to ".enc"
            string outFile = EncrFolder + inFile.Substring
		(startFileName, inFile.LastIndexOf(".") - startFileName) + ".enc";

            using (FileStream outFs = new FileStream(outFile, FileMode.Create))
            {
                outFs.Write(LenK, 0, 4);
                outFs.Write(LenIV, 0, 4);
                outFs.Write(keyEncrypted, 0, lKey);
                outFs.Write(rjndl.IV, 0, lIV);

                // Now write the cipher text using
                // a CryptoStream for encrypting.
                using (CryptoStream outStreamEncrypted = 
		new CryptoStream(outFs, transform, CryptoStreamMode.Write))
                {
                    // By encrypting a chunk at
                    // a time, you can save memory
                    // and accommodate large files.
                    int count = 0;
                    int offset = 0;

                    // blockSizeBytes can be any arbitrary size.
                    int blockSizeBytes = rjndl.BlockSize / 8;
                    byte[] data = new byte[blockSizeBytes];
                    int bytesRead = 0;

                    using (FileStream inFs = new FileStream(inFile, FileMode.Open))
                    {
                        do
                        {
                            count = inFs.Read(data, 0, blockSizeBytes);
                            offset += count;
                            outStreamEncrypted.Write(data, 0, count);
                            bytesRead += blockSizeBytes;
                        }
                        while (count > 0);
                        inFs.Close();
                    }
                    outStreamEncrypted.FlushFinalBlock();
                    outStreamEncrypted.Close();
                }
                outFs.Close();
            }
        }

        private void buttonDecryptFile_Click(object sender, EventArgs e)
        {
            if (rsa == null)
                MessageBox.Show("Key not set.");
            else
            {
                // Display a dialog box to select the encrypted file.
                openFileDialog2.InitialDirectory = EncrFolder;
                if (openFileDialog2.ShowDialog() == DialogResult.OK)
                {
                    string fName = openFileDialog2.FileName;
                    if (fName != null)
                    {
                        FileInfo fi = new FileInfo(fName);
                        string name = fi.Name;
                        DecryptFile(name);
                    }
                }
            }
        }

        private void DecryptFile(string inFile)
        {
            // Create instance of Rijndael for
            // symmetric decryption of the data.
            RijndaelManaged rjndl = new RijndaelManaged();
            rjndl.KeySize = 256;
            rjndl.BlockSize = 256;
            rjndl.Mode = CipherMode.CBC;

            // Create byte arrays to get the length of
            // the encrypted key and IV.
            // These values were stored as 4 bytes each
            // at the beginning of the encrypted package.
            byte[] LenK = new byte[4];
            byte[] LenIV = new byte[4];

            // Construct the file name for the decrypted file.
            string outFile = DecrFolder + inFile.Substring
			(0, inFile.LastIndexOf(".")) + ".txt";

            // Use FileStream objects to read the encrypted
            // file (inFs) and save the decrypted file (outFs).
            using (FileStream inFs = new FileStream(EncrFolder + inFile, FileMode.Open))
            {
                inFs.Seek(0, SeekOrigin.Begin);
                inFs.Seek(0, SeekOrigin.Begin);
                inFs.Read(LenK, 0, 3);
                inFs.Seek(4, SeekOrigin.Begin);
                inFs.Read(LenIV, 0, 3);

                // Convert the lengths to integer values.
                int lenK = BitConverter.ToInt32(LenK, 0);
                int lenIV = BitConverter.ToInt32(LenIV, 0);

                // Determine the start position of
                // the cipher text (startC)
                // and its length(lenC).
                int startC = lenK + lenIV + 8;
                int lenC = (int)inFs.Length - startC;

                // Create the byte arrays for
                // the encrypted Rijndael key,
                // the IV, and the cipher text.
                byte[] KeyEncrypted = new byte[lenK];
                byte[] IV = new byte[lenIV];

                // Extract the key and IV
                // starting from index 8
                // after the length values.
                inFs.Seek(8, SeekOrigin.Begin);
                inFs.Read(KeyEncrypted, 0, lenK);
                inFs.Seek(8 + lenK, SeekOrigin.Begin);
                inFs.Read(IV, 0, lenIV);
                Directory.CreateDirectory(DecrFolder);
                // Use RSACryptoServiceProvider
                // to decrypt the Rijndael key.
                byte[] KeyDecrypted = rsa.Decrypt(KeyEncrypted, false);

                // Decrypt the key.
                ICryptoTransform transform = rjndl.CreateDecryptor(KeyDecrypted, IV)
             using (FileStream outFs = new FileStream(outFile, FileMode.Create))
                {
                    int count = 0;
                    int offset = 0;
                   int blockSizeBytes = rjndl.BlockSize / 8;
                    byte[] data = new byte[blockSizeBytes];
                  inFs.Seek(startC, SeekOrigin.Begin);
                    using (CryptoStream outStreamDecrypted = 
			new CryptoStream(outFs, transform, CryptoStreamMode.Write))
                    {
                        do
                        {
                            count = inFs.Read(data, 0, blockSizeBytes);
                            offset += count;
                            outStreamDecrypted.Write(data, 0, count);
                        }
                        while (count > 0);

                        outStreamDecrypted.FlushFinalBlock();
                        outStreamDecrypted.Close();
                    }
                    outFs.Close();
                }
                inFs.Close();
            }
        }

        private void buttonExportPublicKey_Click(object sender, EventArgs e)
        {
            Directory.CreateDirectory(EncrFolder);
            StreamWriter sw = new StreamWriter(PubKeyFile, false);
            sw.Write(rsa.ToXmlString(false));
            sw.Close();
        }

        private void buttonImportPublicKey_Click(object sender, EventArgs e)
        {
            StreamReader sr = new StreamReader(PubKeyFile);
            cspp.KeyContainerName = keyName;
            rsa = new RSACryptoServiceProvider(cspp);
            string keytxt = sr.ReadToEnd();
            rsa.FromXmlString(keytxt);
            rsa.PersistKeyInCsp = true;
            if (rsa.PublicOnly == true)
                label1.Text = "Key: " + cspp.KeyContainerName + " - Public Only";
            else
                label1.Text = "Key: " + cspp.KeyContainerName + " - Full Key Pair";
            sr.Close();
        }

        private void buttonGetPrivateKey_Click(object sender, EventArgs e)
        {
            cspp.KeyContainerName = keyName;

            rsa = new RSACryptoServiceProvider(cspp);
            rsa.PersistKeyInCsp = true;

            if (rsa.PublicOnly == true)
                label1.Text = "Key: " + cspp.KeyContainerName + " - Public Only";
            else
                label1.Text = "Key: " + cspp.KeyContainerName + " - Full Key Pair";
        }    
    }
}

构建窗体应用程序、检查对象浏览器并设置类的属性（在此情况下为控件）始终是一种良好的实践。但是，此文件是在 .NET Framework 的命令行提示符下构建的。以下是它在使用前的样子。

创建密钥、加密和解密

1. 单击“Create Keys”按钮。标签显示密钥名称，并表明它是一个完整的密钥对。
2. 单击“Export Public Key”按钮。请注意，导出公钥参数不会更改当前密钥。
3. 单击“Encrypt File”按钮并选择一个文件。
4. 单击“Decrypt File”按钮并选择刚刚加密的文件。
5. 检查刚刚解密的文件。
6. 关闭应用程序并重新启动它，以便在下一个场景中测试检索持久化的密钥容器。

使用公钥进行加密

1. 单击“Import Public Key”按钮。标签显示密钥名称，并表明它仅为公共密钥。
2. 单击“Encrypt File”按钮并选择一个文件。
3. 单击“Decrypt File”按钮并选择刚刚加密的文件。这将失败，因为您必须拥有私钥才能解密。

此场景演示了仅拥有公钥来为另一个人加密文件。通常，那个人只会将公钥提供给您，而保留私钥用于解密。

使用私钥进行解密

1. 单击“Get Private Key”按钮。标签显示密钥名称，并表明它是完整的密钥对。
2. 单击“Decrypt File”按钮并选择刚刚加密的文件。这将成功，因为您拥有完整的密钥对来进行解密。

参考文献

• MSDN 库

历史

• 2010 年 4 月 23 日：首次发布