MODULE DE CRYPTAGE VIGENÈRE

Option Explicit

Private Function CombienDeFoisMettreDedans(s As String, key As String) As Integer
 'Verif de la longueur de la clé
 If Len(s) > Len(key) Then
  Dim newLen As Integer
  newLen = Len(key) * (Len(s) / Len(key))
  CombienDeFoisMettreDedans = newLen
  Else
   CombienDeFoisMettreDedans = 1
 End If
End Function

Public Function VigenereEncrypt(s As String, key As String) As String
 'Verif de la longueur de la clé
 If Len(s) > Len(key) Then
  Dim newLen As Integer
  Dim newKey As String
  Dim j As Integer
  newLen = CombienDeFoisMettreDedans(s, key)
  For j = 1 To newLen
   newKey = newKey & key
  Next j
  key = newKey
 End If
 
 Dim i As Integer
 Dim tmp1 As Integer, tmp2 As Integer, tmp3 As String
 For i = 1 To Len(s)
  tmp1 = Asc(Mid(s, i, 1))
  tmp2 = Asc(Mid(key, i, 1))
  If Not tmp1 + tmp2 > 255 Then
   tmp3 = tmp3 & Chr(tmp1 + tmp2)
   Else
    tmp3 = tmp3 & "{?}"
  End If
 Next i
 VigenereEncrypt = tmp3
End Function

Public Function VigenereDecrypt(s As String, key As String)
 'Verif de la longueur de la clé
 If Len(s) > Len(key) Then
  Dim newLen As Integer
  Dim newKey As String
  Dim j As Integer
  newLen = CombienDeFoisMettreDedans(s, key)
  For j = 1 To newLen
   newKey = newKey & key
  Next j
  key = newKey
 End If
 
 s = Replace(s, "{?}", "")
 
 Dim i As Integer, tmp2 As Integer, tmp3 As String
 For i = 1 To Len(s)
  tmp1 = Asc(Mid(s, i, 1))
  tmp2 = Asc(Mid(key, i, 1))
  If tmp1 < tmp2 Then
   tmp3 = tmp3 & "{?}"
   Else
    tmp3 = tmp3 & Chr(tmp1 - tmp2)
  End If
 Next i
 VigenereDecrypt = tmp3
End Function

29 novembre 2006 22:05:12 :

Correction de bugs ... (dans le commentaire de violent_ken)

29 novembre 2006 22:07:09 :

J'avais oublié dans la fonction VigenereDecrypt ...