Encryption & Decryption

Hello everyone, I have been lurking over the forums for some time now, not posting. I have decided to make my own contribution. I don't know if anyone else has done this before or whatever, and I don't know how strong it is..

Code:

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Public Function EncryptF(ByVal Password As String, ByVal Text As String) As String
Dim Temp As Integer
Dim i As Long
If (Len(Password) < Len(Text)) Then
    Temp = Len(Text) / Len(Password)
    For i = 1 To Temp + 1
        Password = Password & Password
    Next i
End If
EncryptF = vbNullString
For i = 1 To Len(Text)
    Temp = Asc(Mid(Text, i, 1)) + Asc(Mid(Password, i, 1))
    EncryptF = EncryptF & Chr(Temp)
Next i
Exit Function
ErrorH:
MsgBox ErrHandle, vbCritical, "Error"
End Function

Public Function DecryptF(ByVal Password As String, ByVal Text As String) As String
On Error GoTo ErrorH
Dim Temp As Integer
Dim i As Long
If (Len(Password) < Len(Text)) Then
    Temp = Len(Text) / Len(Password)
    For i = 1 To Temp + 1
        Password = Password & Password
    Next i
End If
DecryptF = vbNullString
For i = 1 To Len(Text)
    Temp = Asc(Mid(Text, i, 1)) - Asc(Mid(Password, i, 1))
    DecryptF = DecryptF & Chr(Temp)
Next i
Exit Function
ErrorH:
MsgBox ErrHandle, vbCritical, "Error"
End Function


Private Function ErrHandle() As String
If (Err.Description <> "") Then
    ErrHandle = "An error has occured!" & vbNewLine & Err.Number & ") " & Err.Description
End If
End Function


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:)

The source for the Module is above, and there should be an attachment, with it in a module.
Credits go to me!

Warning: Attachment is out of date.

Edit: Oh I forgot to say.. it doesn't work with special characters!

Quote:

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Originally Posted by Vanasha

. . . I don't know if anyone else has done this before or whatever

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A few times:

http://vbforums.com/showthread.php?t=292138
http://vbforums.com/showthread.php?t=404980
http://vbforums.com/showthread.php?t=311963

BTW, nice piece of code :thumb:

Hehe, thanks. I didn't know anyone else did it.. but hey. :D

Here's just a few quick suggestions if you don't mind:

1. Don't pass the Password and Text arguments as ByVal.
2. Don't use string concatenation (String1 = String1 & Something). In your case, the output will always be the same length as the input so you can buffer enough space to store the output before-hand:

EncryptF = Space$(Len(Text))

And instead of:
EncryptF = EncryptF & Chr(Temp)
You could have:
Mid$(EncryptF, i, 1) = Chr$(Temp)

3. Which is important, your code will have problems encrypting some text because there is a possibility the new char (Temp) will exceed 255 (and in decryption, be negative). This will cause an error and won't encrypt the whole text:

Temp = Asc(Mid(Text, i, 1)) + Asc(Mid(Password, i, 1))

If the sum of those is greater than 255 then you will have problems. Or in decrypt, if they are less than 0 then you will get errors.

And use vbNullString instead of "" ;)

Thanks for the advice.

Quote:

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Originally Posted by Mark Gambo

A few times:

http://vbforums.com/showthread.php?t=292138
http://vbforums.com/showthread.php?t=404980
http://vbforums.com/showthread.php?t=311963

BTW, nice piece of code :thumb:

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You forgot my stuff:

http://www.vbforums.com/showthread.php?t=232284
http://www.vbforums.com/showthread.php?t=231798

Quote:

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Originally Posted by CVMichael

You forgot my stuff:

http://www.vbforums.com/showthread.php?t=232284
http://www.vbforums.com/showthread.php?t=231798

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Sorry :blush: :blush: :blush: