<%
Option Explicit
Dim ObjRC4
Set ObjRC4 = New clsRC4
ObjRC4.Key = "Joe"
Response.Write  """" & ObjRC4.Crypt("hello") & """"
Set ObjRC4 = Nothing
' --------------------------------------

Class clsRC4
    
    Private mStrKey
    Private mBytKeyAry(255)
    Private mBytCypherAry(255)
    
    Private Sub InitializeCypher()
        
        Dim lBytJump
        Dim lBytIndex
        Dim lBytTemp
    
        For lBytIndex = 0 To 255
        mBytCypherAry(lBytIndex) = lBytIndex
        Next
        ' Switch values of Cypher arround based off of index and Key value
        lBytJump = 0
        For lBytIndex = 0 To 255
    
            ' Figure index To switch
        lBytJump = (lBytJump + mBytCypherAry(lBytIndex) + mBytKeyAry(lBytIndex)) Mod 256
        
        ' Do the switch
        lBytTemp                    = mBytCypherAry(lBytIndex)
        mBytCypherAry(lBytIndex)    = mBytCypherAry(lBytJump)
        mBytCypherAry(lBytJump)     = lBytTemp
        
        Next
    End Sub
    
    Public Property Let Key(ByRef pStrKey)
        Dim lLngKeyLength
        Dim lLngIndex
        
        If pStrKey = mStrKey Then Exit Property
        lLngKeyLength = Len(pStrKey)
        If lLngKeyLength = 0 Then Exit Property
        mStrKey = pStrKey
        lLngKeyLength = Len(pStrKey)
        For lLngIndex = 0 To 255
        mBytKeyAry(lLngIndex) = Asc(Mid(pStrKey, ((lLngIndex) Mod (lLngKeyLength)) + 1, 1))
        Next
    End Property
    
    Public Property Get Key()
        Key = mStrKey
    End Property
    Public Function Crypt(ByRef pStrMessage)
        Dim lBytIndex
        Dim lBytJump
        Dim lBytTemp
        Dim lBytY
        Dim lLngT
        Dim lLngX
        
        ' Validate data
        If Len(mStrKey) = 0 Then Exit Function
        If Len(pStrMessage) = 0 Then Exit Function
        Call InitializeCypher()
        
        lBytIndex = 0
        lBytJump = 0
        For lLngX = 1 To Len(pStrMessage)
        lBytIndex = (lBytIndex + 1) Mod 256 ' wrap index
        lBytJump = (lBytJump + mBytCypherAry(lBytIndex)) Mod 256 ' wrap J+S()
        
            ' Add/Wrap those two    
        lLngT = (mBytCypherAry(lBytIndex) + mBytCypherAry(lBytJump)) Mod 256
        
        ' Switcheroo
        lBytTemp                    = mBytCypherAry(lBytIndex)
        mBytCypherAry(lBytIndex)    = mBytCypherAry(lBytJump)
        mBytCypherAry(lBytJump)     = lBytTemp
        lBytY = mBytCypherAry(lLngT)
            ' Character Encryption ...
        Crypt = Crypt & Chr(Asc(Mid(pStrMessage, lLngX, 1)) Xor lBytY)
        Next
        
    End Function
End Class
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