rc4.bas

这是一本学习串口编程喝计算机监控的好书里面是用VB开发的源代码

Attribute VB_Name = "RC4"
Public Function RC4(inp As String, key As String) As String
    Dim S(0 To 255) As Byte, K(0 To 255) As Byte, i As Long
    Dim j As Long, temp As Byte, Y As Byte, t As Long, x As Long
    Dim Outp As String
    
    For i = 0 To 255
        S(i) = i
    Next
    
    j = 1
    For i = 0 To 255
        If j > Len(key) Then j = 1
        K(i) = Asc(Mid(key, j, 1))
        j = j + 1
    Next i
    
    j = 0
    For i = 0 To 255
        j = (j + S(i) + K(i)) Mod 256
        temp = S(i)
        S(i) = S(j)
        S(j) = temp
    Next i
    
    i = 0
    j = 0
    For x = 1 To Len(inp)
        i = (i + 1) Mod 256
        j = (j + S(i)) Mod 256
        temp = S(i)
        S(i) = S(j)
        S(j) = temp
        t = (S(i) + (S(j) Mod 256)) Mod 256
        Y = S(t)
        
        Outp = Outp & Chr(Asc(Mid(inp, x, 1)) Xor Y)
    Next
    
    RC4 = Outp
End Function