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Encryption Toolkit

Wrapping the Toolkit to Simplify Development

by Daniel Maddox, Jr. and Christopher Hemminger

NCryptoWrapper

This add-on to the Nickellie Encryption Toolkit was developed to make it even easier to use the Encryption Toolkit to create applications requiring encryption and decryption from Visual Basic and ASP. It provides a simple wrapper class for use in Visual Basic and ASP. This class provides direct support for additional data types and support for "database-safe" encrypted strings. The class is written in Visual Basic for ease of understanding and to simplify the example. The concepts presented in this article could easily be extended to cover Visual C/C++, MFC, eMbedded Visual Basic, and eMbedded Visual C/C++ projects. It is always a good idea to encapsulate this kind of functionality to hide complexity and to make your code easier to understand, debug, and read.

Visual Basic Example

To illustrate the use the of the NCryptoWrapper class, we have built an example application in Visual Basic. The example application provides examples of using the NCryptoWrapper class to encrypt and decrypt "safe" data, encrypt and decrypt "safe" strings, and encrypt and decrypt files. Letís take a look at the example. The example application allows you to enter data to encrypt or decrypt in the Source field, click the appropriate button for the action you intend, and display the results in the Destination field.

Simplify Visual Basic development using the Nickellie Encryption Toolkit

Encrypt and Decrypt String Safe

These options illustrate the use of the member functions EncryptStringSafe and DecryptStringSafe. EncryptStringSafe can be used to encrypt a string and convert the result into a string that is safe, i.e. that consists of only alpha-numeric characters, for insertion into a database, record set, SQL statement, or XML file. The code behind the EncryptStringSafe button uses the EncryptStringSafe member function of the NCryptoWrapper class and displays the results in the destination field. The source code behind this button can be seen in Listing 1.

Dim obj As New NCryptoUtil.NCryptoWrapper
Text2.Text = obj.EncryptStringSafe(Text1.Text, "password")
Listing 1

As you can see, using the NCryptoWrapper and the Nickellie Encryption Toolkit makes this code very simple.

To encrypt the string, we instantiate an NCryptoWrapper object and call EncryptStringSafe, passing the string from the Source field (Text1.Text) and an encryption key. In this example, we use a simple hard-coded encryption key of ďpasswordĒ. For increased security in your application, you may want to implement a more secure method for the generation and storage of your encryption keys. The code behind each of the other buttons is very similar. Now, letís take a look at the wrapper class itself.

ASP Example

To illustrate the use of the NCryptoWrapper class in ASP, we have built a sample ASP page similiar to the VB example application discussed above. The ASP example provides examples of using the NCryptoWrapper class to encrypt and decrypt "safe" strings. Letís take a look at the example. The example allows you to enter data to encrypt or decrypt in the Source field, select Encrypt or Decrypt, click Submit, and display the results in the Destination field.

Simplify Visual Basic development using the Nickellie Encryption Toolkit

Like the VB example, the ASP page uses EncryptStringSafe and DecryptStringSafe. The page posts to itself, and the code to encrypt and decrypt the data can be seen in Listing 2. As you can see, it would be fairly easy to extend this example to write the encrypted data into database or pass it to another object for further processing.

    'data was posted to encrypt or decrypt
    sourcedata = Request.Form.Item("source")
    'Create an NCryptoWrapper Object
    Set obj = Server.CreateObject("NCryptoUtil.NCryptoWrapper")
    If Request.Form.Item("action") = "Decrypt" Then
        'user selected decrypt, call DecryptStringSafe
        resultdata = obj.DecryptStringSafe(sourcedata, "password")
    Else
        'user selected encrypt, call EncryptStringSafe
        resultdata = obj.EncryptStringSafe(sourcedata, "password")
    End If
Listing 2

NCryptoWrapper Class

The NCryptoWrapper class provides a simple wrapper for the NCrypto object of the Nickellie Encryption Toolkit. The NCryptoWrapper class provides a simple but powerful interface for adding encryption capabilities to your Visual Basic and ASP applications. Essentially, the encryption methods of this class do three things:

  1. Convert the given data to the appropriate type.
  2. Encrypt the data using the appropriate function call to the Nickellie Encryption Toolkit.
  3. Translate the data into a database safe string of alphanumeric characters.

All of the source code for this wrapper class is included in the download of the project so you can modify as needed for your own applications. In the example above, we used EncryptStringSafe to encrypt a string and convert the encrypted string to a "database-safe" string. Now letís look at the details of this function.

EncryptDataSafe Method

The example we discussed above used EncryptStringSafe. The EncryptStringSafe method simply call the EncryptDataSafe method as follows:

EncryptStringSafe = EncryptDataSafe(inData, password)

Letís look at the implementation of EncryptDataSafe in Listing 3. This function accepts the data to encrypt as a string and returns the encrypted data as a "safe" encrypted string. First, EncryptDataSafe checks the data type of the incoming data and converts it to a Byte Array.

If (VarType(inData) = vbString) Then
    'The inbound data is a string, so we must convert to an
    'array first.
    'Convert the String to a Byte Array
    StrToByte SrcByte(), CStr(inData)

ElseIf ((VarType(inData) = vbArray + vbByte) Or_
    ((VarType(inData) = vbArray + vbVariant) _
    And (VarType(inData(0)) = vbByte))) Then
    'The inbound data is a variant array of bytes or a
    'variant array of variant bytes.
    'We will just copy it directly into the SrcByte array
    'with a conversion.
    'The inData array must be base 0
    ReDim SrcByte(0 To UBound(inData))
    For idx = 0 To UBound(SrcByte)
        SrcByte(idx) = CByte(inData(idx))
    Next
Else
    Err.Raise ncNotSupported, "NCryptoUtil.NCryptoWrapper", _
        "The inData argument is not a supported data type."
    Exit Function
End If
Listing 3

As you can see, the above code uses the function StrToByte to convert from a String to a Byte Array. This function has been implemented as a private method of the NCryptoWrapper class (see Listing 4). It should be pretty easy to extend the code to handle just about any custom data type that you wish to handle in your own applications.

Private Sub StrToByte(dest() As Byte, src As String)
    Dim idx As Integer
    'We are shifting from a Base 1 String to a Base 0 Array
    ReDim dest(0 To Len(src) - 1)
    For idx = 1 To Len(src)
        'Converts the Unicode character to an ASCII character
        'and places it in the byte array
        dest(idx - 1) = AscB(Mid(src, idx, 1))
    Next
End Sub
Listing 4

After converting the incoming data to a Byte Array, the data is encrypted via a call to the NCrypto object (from the Nickellie Encryption Toolkit) as follows:

Crypto.EncryptData EncByte(), SrcByte(), _
    UBound(SrcByte) + 1, pw

The encrypted data is returned as a Byte Array into EncByte(). This encrypted data is likely to contain characters that will cause errors if you attempt to convert this data to a string and store it in a database. As such, this function converts the encrypted data to a "database-safe" encrypted string by calling the function in Listing 5 as follows:

ByteToSafeStr EncString, EncByte()

Like StrToByte, ByteToSafeStr has been implemented as a private method of the NCrytpoWrapper class. The function converts the encrypted byte data to a string consisting of only alphanumeric characters.

Private Sub ByteToSafeStr(dest As String, src() As Byte)
    Dim idx As Integer
    dest = ""
    For idx = 0 To UBound(src)
        'Converts the ASCII characters in the byte array into
        'a safe string of Hexadecimal text
        dest = dest + Right("00" + Hex(src(idx)), 2)
    Next
End Sub
Listing 5

After this conversion, EncryptDataSafe returns the encrypted safe string. The string can then be used as necessary within the application. In the example, the string is displayed to the screen.

Conclusion

The NCryptoWrapper class makes using the Nickellie Encryption Toolkitís NCrypto Object a snap from any Visual Basic or ASP application.

Installation Notes

To install the examples discussed in the article, follow these steps:

  1. Download and install the Nickellie Encryption Toolkit (any version).
  2. Download the source code for this article which includes source code for the NCryptoWrapper class, the VB example, and the ASP example.
  3. Add a new COM+ application and add the NCryptoUtil.NCryptoWrapper component and the NCrypto component to that application. For step by step instructions, read our instructions on Configuring the NCryptoWrapper in COM+.

NOTE: To use the ASP example, you will need to install the Nickellie Encryption Toolkit on your web server and ensure that the web user has proper permissions to make calls into the Cryptography API. With some installations, this varies from the default settings. If the web user does not have the necessary permissions, the example will produce a string of zeroes for any string you attempt to encrypt. The most common solution to this problem is to grant access to advapi32.dll to the IUSR and IWAM accounts used by IIS. If you encounter this problem on your system and need assistance, please contact Nickellie.

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