Here is a basic version of an encryption sscheme i devloped.
If you have the time and the knowledge please test it.
[list=A][*]Is it a strong encryption?[*]Did you brake it? How?[*]Any ideas for improvement?[/list=A]


Code:
Global dKey as Double,sKey as Double,D(255) As Byte
Function Encrypt(OriginalFile)
        'Promt user to enter a Key: call Key(text1.text) 
        sfile=OriginalFile 
        Rnd (-dKey): Randomize dKey
        
        xfile = sfile & ".stdenc"
        Open sfile For Random As #1 Len = 1
        lenfile = LOF(1)
        Close
        
        ReDim C(lenfile) As Byte, x(lenfile) As Byte
        Open sfile For Binary As #1
        Get #1, 1, C()
        Close
        y = 0
        
        For i = 1 To lenfile
            y = y + 1
            y = y Mod 255 + 1
            x(i) = C(i) Xor D(y)
        Next i
        
        Open xfile For Binary As #1
        Put #1, 1, x()
        Close
End Function

Private Sub Key (x as String)

For i = 1 To (Len(x) - 1)
    t = t + Asc(Mid(x, i, 1))
Next i
t = t - Asc(Mid(x, Len(x), 1))
t = t ^ 2 - t
Rnd (-t)
Randomize t

sKey = Int(Rnd * 2123234345) + 2000398
dKey = Int(sKey / 1000 + 603)

Rnd (-sKey)
Randomize sKey

For i = 1 To 255
    g = Int(Rnd * 255) + 1
    h = Int(Rnd * 255) + 1
    D(i) = g Xor h
Next i

End Sub
Let me know what you think