Update [Alg].Create() samples for 3DES/RC2.

snippets/cpp/VS_Snippets_CLR/Cryptography.3DES.Create.File/CPP/fileexample.cpp

@@ -1,119 +1,146 @@
-
 // <SNIPPET1>
 using namespace System;
+using namespace System::IO;
 using namespace System::Security::Cryptography;
 using namespace System::Text;
-using namespace System::IO;
-void EncryptTextToFile( String^ Data, String^ FileName, array<Byte>^Key, array<Byte>^IV )
+
+void EncryptTextToFile(String^ text, String^ path, array<Byte>^ key, array<Byte>^ iv);
+String^ DecryptTextFromFile(String^ path, array<Byte>^ key, array<Byte>^ iv);
+
+int main()
 {
-   try
-   {
-
-      // Create or open the specified file.
-      FileStream^ fStream = File::Open( FileName, FileMode::OpenOrCreate );
-
-      // Create a new TripleDES object.
-      TripleDES^ tripleDESalg = TripleDES::Create();
-
-      // Create a CryptoStream using the FileStream 
-      // and the passed key and initialization vector (IV).
-      CryptoStream^ cStream = gcnew CryptoStream( fStream,tripleDESalg->CreateEncryptor( Key, IV ),CryptoStreamMode::Write );
-
-      // Create a StreamWriter using the CryptoStream.
-      StreamWriter^ sWriter = gcnew StreamWriter( cStream );
-
-      // Write the data to the stream 
-      // to encrypt it.
-      sWriter->WriteLine( Data );
-
-      // Close the streams and
-      // close the file.
-      sWriter->Close();
-      cStream->Close();
-      fStream->Close();
-   }
-   catch ( CryptographicException^ e ) 
-   {
-      Console::WriteLine( "A Cryptographic error occurred: {0}", e->Message );
-   }
-   catch ( UnauthorizedAccessException^ e ) 
-   {
-      Console::WriteLine( "A file access error occurred: {0}", e->Message );
-   }
+    try
+    {
+        array<Byte>^ key;
+        array<Byte>^ iv;
+
+        // Create a new TripleDES object to generate a random key
+        // and initialization vector (IV).
+        {
+            TripleDES^ tripleDes;
+
+            try
+            {
+                tripleDes = TripleDES::Create();
+                key = tripleDes->Key;
+                iv = tripleDes->IV;
+            }
+            finally
+            {
+                delete tripleDes;
+            }
+        }
+
+        // Create a string to encrypt.
+        String^ original = "Here is some data to encrypt.";
+        // The name/path of the file to write.
+        String^ filename = "CText.enc";
+
+        // Encrypt the string to a file.
+        EncryptTextToFile(original, filename, key, iv);
+
+        // Decrypt the file back to a string.
+        String^ decrypted = DecryptTextFromFile(filename, key, iv);
 
+        // Display the decrypted string to the console.
+        Console::WriteLine(decrypted);
+    }
+    catch (Exception^ e)
+    {
+        Console::WriteLine(e->Message);
+    }
 }
 
-String^ DecryptTextFromFile( String^ FileName, array<Byte>^Key, array<Byte>^IV )
+void EncryptTextToFile(String^ text, String^ path, array<Byte>^ key, array<Byte>^ iv)
 {
-   try
-   {
-
-      // Create or open the specified file. 
-      FileStream^ fStream = File::Open( FileName, FileMode::OpenOrCreate );
-
-      // Create a new TripleDES object.
-      TripleDES^ tripleDESalg = TripleDES::Create();
-
-      // Create a CryptoStream using the FileStream 
-      // and the passed key and initialization vector (IV).
-      CryptoStream^ cStream = gcnew CryptoStream( fStream,tripleDESalg->CreateDecryptor( Key, IV ),CryptoStreamMode::Read );
-
-      // Create a StreamReader using the CryptoStream.
-      StreamReader^ sReader = gcnew StreamReader( cStream );
-
-      // Read the data from the stream 
-      // to decrypt it.
-      String^ val = sReader->ReadLine();
-
-      // Close the streams and
-      // close the file.
-      sReader->Close();
-      cStream->Close();
-      fStream->Close();
-
-      // Return the string. 
-      return val;
-   }
-   catch ( CryptographicException^ e ) 
-   {
-      Console::WriteLine( "A Cryptographic error occurred: {0}", e->Message );
-      return nullptr;
-   }
-   catch ( UnauthorizedAccessException^ e ) 
-   {
-      Console::WriteLine( "A file access error occurred: {0}", e->Message );
-      return nullptr;
-   }
+    FileStream^ fStream = nullptr;
+    TripleDES^ tripleDes = nullptr;
+    ICryptoTransform^ encryptor = nullptr;
+    CryptoStream^ cStream = nullptr;
 
+    try
+    {
+        // Create or open the specified file.
+        fStream = File::Open(path, FileMode::Create);
+        // Create a new TripleDES object.
+        tripleDes = TripleDES::Create();
+        // Create a TripleDES encryptor from the key and IV
+        encryptor = tripleDes->CreateEncryptor(key, iv);
+        // Create a CryptoStream using the FileStream and encryptor
+        cStream = gcnew CryptoStream(fStream, encryptor, CryptoStreamMode::Write);
+
+        // Convert the provided string to a byte array.
+        array<Byte>^ toEncrypt = Encoding::UTF8->GetBytes(text);
+
+        // Write the byte array to the crypto stream.
+        cStream->Write(toEncrypt, 0, toEncrypt->Length);
+    }
+    catch (CryptographicException^ e)
+    {
+        Console::WriteLine("A Cryptographic error occurred: {0}", e->Message);
+        throw;
+    }
+    finally
+    {
+        if (cStream != nullptr)
+            delete cStream;
+
+        if (encryptor != nullptr)
+            delete encryptor;
+
+        if (tripleDes != nullptr)
+            delete tripleDes;
+
+        if (fStream != nullptr)
+            delete fStream;
+    }
 }
 
-int main()
+String^ DecryptTextFromFile(String^ path, array<Byte>^ key, array<Byte>^ iv)
 {
-   try
-   {
-
-      // Create a new TripleDES object to generate a key
-      // and an initialization vector (IV).
-      TripleDES^ TripleDESalg = TripleDES::Create();
-
-      // Create a string to encrypt.
-      String^ sData = "Here is some data to encrypt.";
-      String^ FileName = "CText.txt";
-
-      // Encrypt text to a file using the file name, key, and IV.
-      EncryptTextToFile( sData, FileName, TripleDESalg->Key, TripleDESalg->IV );
-
-      // Decrypt the text from a file using the file name, key, and IV.
-      String^ Final = DecryptTextFromFile( FileName, TripleDESalg->Key, TripleDESalg->IV );
-
-      // Display the decrypted string to the console.
-      Console::WriteLine( Final );
-   }
-   catch ( Exception^ e ) 
-   {
-      Console::WriteLine( e->Message );
-   }
+    FileStream^ fStream = nullptr;
+    TripleDES^ tripleDes = nullptr;
+    ICryptoTransform^ decryptor = nullptr;
+    CryptoStream^ cStream = nullptr;
+    StreamReader^ reader = nullptr;
+
+    try
+    {
+        // Open the specified file
+        fStream = File::OpenRead(path);
+        // Create a new TripleDES object.
+        tripleDes = TripleDES::Create();
+        // Create a TripleDES decryptor from the key and IV
+        decryptor = tripleDes->CreateDecryptor(key, iv);
+        // Create a CryptoStream using the FileStream and decryptor
+        cStream = gcnew CryptoStream(fStream, decryptor, CryptoStreamMode::Read);
+        // Create a StreamReader to turn the bytes back into text
+        reader = gcnew StreamReader(cStream, Encoding::UTF8);
+
+        // Read back all of the text from the StreamReader, which receives
+        // the decrypted bytes from the CryptoStream, which receives the
+        // encrypted bytes from the FileStream.
+        return reader->ReadToEnd();
+    }
+    catch (CryptographicException^ e)
+    {
+        Console::WriteLine("A Cryptographic error occurred: {0}", e->Message);
+        throw;
+    }
+    finally
+    {
+        if (cStream != nullptr)
+            delete cStream;
+
+        if (decryptor != nullptr)
+            delete decryptor;
+
+        if (tripleDes != nullptr)
+            delete tripleDes;
 
+        if (fStream != nullptr)
+            delete fStream;
+    }
 }
 
 // </SNIPPET1>