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Imports System.Reflection

Imports System.Text

Imports System.Security.Cryptography

' Sign the assembly with a Strong Name Key created with the .net Framework SDK 

' Strong Name Tool (Sn.exe).   This is important - it ensures that your assembly identity

' is sufficiently strong; so that it will not confict with other assemblies.

' 

' Sn.exe -k DotNetCryptoCOM.snk

'

' During Compilation and Build, VS.net will look for the strong name key in the same

' location as your solution (.sln) file.   You may have to move the .snk file there before build.

'

' Note: If you see the 'Error creating assembly manifest' during compilation, 

'            you may have copied in the .snk file while the solution was open. You should

'            try closing and re-opening the solution before the DLL will build successfully.

<Assembly: AssemblyKeyFileAttribute("DotNetCryptoCOM.snk")> 

' Note: You will also need to ensure that the project is not set to register for 

'            COM interop at this point.   To check, go to Project Properties, 

'            Config Properties, Build, and make sure that the "Register for COM Interop" 

'            is UNCHECKED.

'            We will manually register the signed assembly for COM interop using the RegAsm tool

'            after the DLL has been built.

Public Class CryptoClass

       ' m_CryptoServiceProvider Defines a wrapper object to access the cryptographic service provider

       ' This example uses the Data Encryption Standard (DES) symmetric cryptographic algorithm

       '

       ' Implementators that require use of other symmetric CryptoServiceProviders, 

       ' simply need to replace the DESCryptServiceProvider with one of the following

       ' .Net Symmetric Cryptographic Algorithm Implementations:

       '   DESCryptoServiceProvider

       '   RijndaelManaged 

       '   RC2CryptoServiceProvider

       '   TripleDESCryptoServiceProvider

       Private m_CryptoServiceProvider As DESCryptoServiceProvider

       ' Create the new CryptoServiceProvider

       Public Sub New()

              ' Replace the DESCryptoServiceProvider with another symmetric algoritm implementation if desired

              m_CryptoServiceProvider = New DESCryptoServiceProvider

       End Sub

       ' Destroy the CryptoServiceProvider

       Protected Overrides Sub Finalize()

              m_CryptoServiceProvider = Nothing

              MyBase.Finalize()

       End Sub

       Public Function Encrypt(ByVal Source As String, ByVal Key As String) As String

              Dim bytIn As Byte() = System.Text.Encoding.ASCII.GetBytes(Source)

              ' Create a MemoryStream

              Dim ms As System.IO.MemoryStream = New System.IO.MemoryStream

              ' Ensure that the key is of legal size for the crypto algorithm

              Dim bytKey As Byte() = GetLegalKey(Key)

              ' Set the private key

              m_CryptoServiceProvider.Key = bytKey

              m_CryptoServiceProvider.IV = bytKey

              ' Create an Encryptor from the Provider Service instance

              Dim encrypto As ICryptoTransform = m_CryptoServiceProvider.CreateEncryptor()

              ' Create Crypto Stream that transforms a stream using the encryption

              Dim cs As CryptoStream = New CryptoStream(ms, encrypto, CryptoStreamMode.Write)

              ' Write out encrypted content into MemoryStream

              cs.Write(bytIn, 0, bytIn.Length)

              cs.Close()

              ' Convert into Base64

              Dim encrypted As Byte()

              encrypted = ms.ToArray

              Return System.Convert.ToBase64String(encrypted, 0, encrypted.Length)

       End Function

       Public Function Decrypt(ByVal Source As String, ByVal Key As String) As String

              ' Convert from Base64 to binary

              Dim bytIn As Byte() = System.Convert.FromBase64String(Source)

              ' Create a MemoryStream with the input

              Dim ms As System.IO.MemoryStream = New System.IO.MemoryStream(bytIn, 0, bytIn.Length)

              Dim bytKey As Byte() = GetLegalKey(Key)

              ' Set the private key

              m_CryptoServiceProvider.Key = bytKey

              m_CryptoServiceProvider.IV = bytKey

              ' Create a Decryptor from the Provider Service instance

              Dim encrypto As ICryptoTransform = m_CryptoServiceProvider.CreateDecryptor()

              ' Create Crypto Stream that transforms a stream using the decryption

              Dim cs As CryptoStream = New CryptoStream(ms, encrypto, CryptoStreamMode.Read)

              ' Read out the result from the Crypto Stream

              Dim sr As System.IO.StreamReader = New System.IO.StreamReader(cs)

              Return sr.ReadToEnd()

       End Function

       ' Depending on the legal key size limitations of a specific CryptoService provider

       ' and length of the private key provided, padding the secret key with space character

       ' to meet the legal size of the algorithm.

       Private Function GetLegalKey(ByVal Key As String) As Byte()

              Dim sTemp As String

              If (m_CryptoServiceProvider.LegalKeySizes.Length > 0) Then

                     Dim minSize As Integer = m_CryptoServiceProvider.LegalKeySizes(0).MinSize

                     Dim maxsize As Integer = m_CryptoServiceProvider.LegalKeySizes(0).MaxSize

                     ' Key sizes are in bits

                     If ((Key.Length * 8) > maxsize) Then

                            ' Trim key to max-key size

                            sTemp = Key.Substring(0, (maxsize / 8))

                     Else

                            If ((Key.Length * 8) < minSize) Then

                                   ' Pad small key to minsize length with space

                                   sTemp = Key.PadRight((minSize / 8), " ")

                            Else

                                   Dim lesssize As Integer = 0

                                   Dim moresize As Integer = minSize

                                   ' Get nearest Skipsize increment between minsize and maxsize that

                                   ' corresponds with key length

                                   Do While ((Key.Length * 8) > moresize)

                                          lesssize = moresize

                                          moresize += m_CryptoServiceProvider.LegalKeySizes(0).SkipSize

                                   Loop

                                   ' Pad mid-range key if necessary

                                   sTemp = Key.PadRight((moresize / 8), " ")

                            End If

                     End If

              Else

                            sTemp = Key

              End If

              ' Convert the secret key to byte array

              Return ASCIIEncoding.ASCII.GetBytes(sTemp)

       End Function

End Class

' Create a new CryptoServiceProvider

Set oCryptoProvider = CreateObject("DotNetCryptoCOM.CryptoClass")

' Note: That the default CryptoServiceProvider for this class (in this case DES)

' has a key-size of exactly 64 bits. Other symmetric algorithm implementations

' require keys of different sizes, and increments. 

' The CryptoClass caters for all of these different key sizes through the

' LegalKeySizes symmetric algorithm property. Keys provided to the class are checked

' against the known minimum, maximum and skip key sizes for each algorithm. 

' Long keys will be clipped, short keys will be padded with spaces.

' Data to encrypt:

strRawData = "All your base are belong to us"

' Encrypt the data with key "SECRETKEY"

strEncryptedData = oCryptoProvider.Encrypt(strRawData,"SECRETKEY")

' Decrypt the encrypted data with the same key

strDecryptedData = oCryptoProvider.Decrypt(strEncryptedData,"SECRETKEY")

' Write the a custom message to Custom01 (Fields.VarCustom01)

Fields.VarCustom01 = "Encrypted Data: " & strEncryptedData & vbCrLf & "Decrypted Data: " & strDecryptedData

' Destroy the CryptoServiceProvider

Set oCryptoProvider = Nothing

' Create a new CryptoServiceProvider

Set oCryptoProvider = CreateObject("DotNetCryptoCOM.CryptoClass")

' Note: That the default CryptoServiceProvider for this class (in this case DES)

' has a key-size of exactly 64 bits. Other symmetric algorithm implementations

' require keys of different sizes, and increments. 

' The CryptoClass caters for all of these different key sizes through the

' LegalKeySizes symmetric algorithm property. Keys provided to the class are checked

' against the known minimum, maximum and skip key sizes for each algorithm. 

' Long keys will be clipped, short keys will be padded with spaces.

' Data to encrypt:

strRawData = "All your base are belong to us"

' Encrypt the data with key "SECRETKEY"

strEncryptedData = oCryptoProvider.Encrypt(strRawData,"SECRETKEY")

' Decrypt the encrypted data with the same key

strDecryptedData = oCryptoProvider.Decrypt(strEncryptedData,"SECRETKEY")

' Message Popup

MsgBox "Encrypted Data: " & strEncryptedData & vbCrLf & "Decrypted Data: " & strDecryptedData

' Destroy the CryptoServiceProvider

Set oCryptoProvider = Nothing