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Sending and receiving public keys Sending your public key via email. To receive encrypted messages from other people, you must first send them your public key: Compose the message. Select OpenPGP from the Thunderbird menu bar and select Attach My Public Key. Send the email as usual. Receiving a public key via email. Concerning the PGP Key Generator, we DO NOT record any data: no e-mail address, no password and no messages. If you wish to place an order, your details will be requested. Some services require the use of cookies to work, and these cookies can not be disabled: - The very site of wp2pgpmail, if you identify yourself by logging into your account. To create keys, encrypt, and decrypt. Click the Create Keys button. The label displays the key name and shows that it is a full key pair. Click the Export Public Key button. Note that exporting the public key parameters does not change the current.

1. Email Encryption Gmail

This walkthrough demonstrates how to encrypt and decrypt content. The code examples are designed for a Windows Forms application. This application does not demonstrate real world scenarios, such as using smart cards. Instead, it demonstrates the fundamentals of encryption and decryption.

This walkthrough uses the following guidelines for encryption:

• Use the RijndaelManaged class, a symmetric algorithm, to encrypt and decrypt data by using its automatically generated Key and IV.

• Use the RSACryptoServiceProvider, an asymmetric algorithm, to encrypt and decrypt the key to the data encrypted by RijndaelManaged. Asymmetric algorithms are best used for smaller amounts of data, such as a key.

  Note

  If you want to protect data on your computer instead of exchanging encrypted content with other people, consider using the ProtectedData or ProtectedMemory classes.

The following table summarizes the cryptographic tasks in this topic.

Prerequisites

You need the following components to complete this walkthrough:

• References to the System.IO and System.Security.Cryptography namespaces.

Creating a Windows Forms Application

Most of the code examples in this walkthrough are designed to be event handlers for button controls. The following table lists the controls required for the sample application and their required names to match the code examples.

Double-click the buttons in the Visual Studio designer to create their event handlers.

Declaring Global Objects

Add the following code to the Form's constructor. Edit the string variables for your environment and preferences.

Creating an Asymmetric Key

This task creates an asymmetric key that encrypts and decrypts the RijndaelManaged key. This key was used to encrypt the content and it displays the key container name on the label control.

Add the following code as the Click event handler for the Create Keys button (buttonCreateAsmKeys_Click).

Encrypting a File

This task involves two methods: the event handler method for the Encrypt File button (buttonEncryptFile_Click) and the EncryptFile method. The first method displays a dialog box for selecting a file and passes the file name to the second method, which performs the encryption.

The encrypted content, key, and IV are all saved to one FileStream, which is referred to as the encryption package.

The EncryptFile method does the following:

1. Creates a RijndaelManaged symmetric algorithm to encrypt the content.

2. Creates an RSACryptoServiceProvider object to encrypt the RijndaelManaged key.

3. Uses a CryptoStream object to read and encrypt the FileStream of the source file, in blocks of bytes, into a destination FileStream object for the encrypted file.

4. Determines the lengths of the encrypted key and IV, and creates byte arrays of their length values.

5. Writes the Key, IV, and their length values to the encrypted package.

The encryption package uses the following format:

• Key length, bytes 0 - 3

• IV length, bytes 4 - 7

• Encrypted key

• IV

• Cipher text

You can use the lengths of the key and IV to determine the starting points and lengths of all parts of the encryption package, which can then be used to decrypt the file.

Add the following code as the Click event handler for the Encrypt File button (buttonEncryptFile_Click).

Add the following EncryptFile method to the form.

Decrypting a File

This task involves two methods, the event handler method for the Decrypt File button (buttonDecryptFile_Click), and the DecryptFile method. The first method displays a dialog box for selecting a file and passes its file name to the second method, which performs the decryption.

The Decrypt method does the following:

1. Creates a RijndaelManaged symmetric algorithm to decrypt the content.

2. Reads the first eight bytes of the FileStream of the encrypted package into byte arrays to obtain the lengths of the encrypted key and the IV.

3. Extracts the key and IV from the encryption package into byte arrays.

4. Creates an RSACryptoServiceProvider object to decrypt the RijndaelManaged key.

5. Uses a CryptoStream object to read and decrypt the cipher text section of the FileStream encryption package, in blocks of bytes, into the FileStream object for the decrypted file. When this is finished, the decryption is completed.

Add the following code as the Click event handler for the Decrypt File button.

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Add the following DecryptFile method to the form.

Exporting a Public Key

This task saves the key created by the Create Keys button to a file. It exports only the public parameters.

This task simulates the scenario of Alice giving Bob her public key so that he can encrypt files for her. He and others who have that public key will not be able to decrypt them because they do not have the full key pair with private parameters.

Add the following code as the Click event handler for the Export Public Key button (buttonExportPublicKey_Click).

Importing a Public Key

Email Encryption Gmail

This task loads the key with only public parameters, as created by the Export Public Key button, and sets it as the key container name.

This task simulates the scenario of Bob loading Alice's key with only public parameters so he can encrypt files for her.

Add the following code as the Click event handler for the Import Public Key button (buttonImportPublicKey_Click).

Getting a Private Key

This task sets the key container name to the name of the key created by using the Create Keys button. The key container will contain the full key pair with private parameters.

This task simulates the scenario of Alice using her private key to decrypt files encrypted by Bob.

Add the following code as the Click event handler for the Get Private Key button (buttonGetPrivateKey_Click).

Testing the Application

After you have built the application, perform the following testing scenarios.

To create keys, encrypt, and decrypt

1. Click the Create Keys button. The label displays the key name and shows that it is a full key pair.

2. Click the Export Public Key button. Note that exporting the public key parameters does not change the current key.

3. Click the Encrypt File button and select a file.

4. Click the Decrypt File button and select the file just encrypted.

5. Examine the file just decrypted.

6. Close the application and restart it to test retrieving persisted key containers in the next scenario.

To encrypt using the public key

1. Click the Import Public Key button. The label displays the key name and shows that it is public only.

2. Click the Encrypt File button and select a file.

3. Click the Decrypt File button and select the file just encrypted. This will fail because you must have the private key to decrypt.

This scenario demonstrates having only the public key to encrypt a file for another person. Typically that person would give you only the public key and withhold the private key for decryption.

To decrypt using the private key

1. Click the Get Private Key button. The label displays the key name and shows whether it is the full key pair.

2. Click the Decrypt File button and select the file just encrypted. This will be successful because you have the full key pair to decrypt.

See also