Implement Advanced Data Encryption Techniques with Excel VBA

We will focus on the implementation of AES (Advanced Encryption Standard) encryption, which is commonly used in many security systems.

Overview of AES Encryption

AES is a symmetric encryption algorithm, meaning the same key is used for both encryption and decryption. It operates on blocks of data (128 bits) and supports key sizes of 128, 192, or 256 bits.

Since Excel VBA doesn’t natively support AES encryption, we can make use of external libraries such as the Windows Crypto API or a VBA-compatible AES library. For the purpose of this example, we’ll use a simple AES library called VBA-AES, which you can easily import into your project.

Steps to Implement AES Encryption in Excel VBA

1. Download and Import the AES VBA Library:
   • Download a VBA-compatible AES library (you can find one on GitHub or other sources such as VBA-AES GitHub repository).
   • Import the module into your Excel VBA project by opening the VBA editor (Alt + F11), going to Insert > Module, and then pasting the library code into the module.
2. Add Code for AES Encryption and Decryption: After importing the AES library into your project, you can start writing the encryption and decryption functions.

Here’s a detailed VBA example:

Step 1: Create a Module for AES Encryption

Option Explicit
' Add a reference to the AES encryption library before using it
' Paste the AES library module code here.
' Encryption Function
Public Function EncryptData(ByVal plainText As String, ByVal key As String) As String
    Dim encryptedText As String
    Dim aes As Object   
    ' Create an AES object
    Set aes = CreateObject("VBA_AES.AES")   
    ' Encrypt the data using the provided key
    encryptedText = aes.Encrypt(plainText, key)   
    ' Return the encrypted data (Base64 encoded)
    EncryptData = encryptedText
End Function

' Decryption Function
Public Function DecryptData(ByVal encryptedText As String, ByVal key As String) As String
    Dim decryptedText As String
    Dim aes As Object   
    ' Create an AES object
    Set aes = CreateObject("VBA_AES.AES")   
    ' Decrypt the data using the provided key
    decryptedText = aes.Decrypt(encryptedText, key)  
    ' Return the decrypted dat
    DecryptData = decryptedText
End Function

Explanation of the Code:

• EncryptData Function:
  • Parameters:
    • plainText: This is the data you want to encrypt (it should be a string).
    • key: This is the secret key used for encryption. It can be a string of any length, but for AES-128, it should be 16 bytes long, for AES-192, it should be 24 bytes long, and for AES-256, it should be 32 bytes long.
  • The EncryptData function creates an AES object, uses the Encrypt method, and then returns the encrypted text. This text is usually returned in a Base64 encoded format so that it’s easy to handle in text format.
• DecryptData Function:
  • Parameters:
    • encryptedText: This is the encrypted data (Base64 encoded) that needs to be decrypted.
    • key: The same key used for encryption is required for decryption.
  • The DecryptData function creates an AES object, uses the Decrypt method, and returns the original plaintext.

Step 2: Test Encryption and Decryption

You can create a subroutine to test the encryption and decryption process:

Sub TestEncryption()
    Dim plainText As String
    Dim encryptedText As String
    Dim decryptedText As String
    Dim key As String 
    ' Set your plain text and encryption key
    plainText = "Hello, this is a test of AES encryption!"
    key = "myencryptionkey123" ' 16 characters for AES-128   
    ' Encrypt the text
    encryptedText = EncryptData(plainText, key)
    Debug.Print "Encrypted Text: " & encryptedText   
    ' Decrypt the text
    decryptedText = DecryptData(encryptedText, key)
    Debug.Print "Decrypted Text: " & decryptedText
End Sub

Explanation of the TestEncryption Subroutine:

1. plainText: The text you want to encrypt.
2. key: A secret key used for encryption (make sure it follows the correct length for AES-128, AES-192, or AES-256).
3. EncryptData: This function encrypts the plainText using the provided key.
4. DecryptData: This function decrypts the encryptedText back to the original plainText.

Step 3: Running the Test

1. Open the Immediate Window in the VBA editor (Ctrl + G).
2. Run the TestEncryption subroutine.
3. Check the output in the Immediate Window. You should see the encrypted text (in Base64 format) and the decrypted text, which should match the original plainText.

Conclusion

This VBA code allows you to implement AES encryption in Excel. The main steps include importing an AES library, writing functions for encryption and decryption, and testing them with a sample data. By doing so, you can securely store and transmit sensitive data in Excel using AES encryption.

Notes:

• Security: The security of AES encryption depends on the secrecy and strength of the encryption key. Never hard-code sensitive keys in the code for production applications. Use a secure method to generate and store the key.
• Library: The VBA_AES.AES object referenced in the example is just one example of an AES library that can be used in VBA. There are other libraries available that you can use depending on your needs.