一個利用隨機(jī)數(shù)加密字串的算法

每個字節(jié)加密后有6種結(jié)果（占兩個字節(jié)，如果需要大于6種的話，就要多用1個字節(jié)，即占3 個字節(jié)），也就是說如果字串占n個字節(jié)的話，可能產(chǎn)生的結(jié)果為6的n次方個，這個算法*的強(qiáng)度不大，大家可以完善一下：
    ’’窗體上一個按鈕，兩個listbox
    Option Explicit
    Private Sub Command1_Click()
     Dim i As Long
     Dim s As String
     For i = 1 To 100
     s = encode("這是一個測試 hello world")
     List1.AddItem s
     s = decode(s)
     List2.AddItem s
     Next
    End Sub
    Private Function encode(ByVal s As String) As String ’’加密
     If Len(s) = 0 Then Exit Function
     Dim buff() As Byte
     buff = StrConv(s, vbFromUnicode)
     Dim i As Long
     Dim j As Byte
     Dim k As Byte, m As Byte
     Dim mstr As String
     mstr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz"
     Dim outs As String
     i = UBound(buff) + 1
     outs = Space(2 * i)
     Dim temps As String
     For i = 0 To UBound(buff)
     Randomize Time
     j = CByte(5 * (Math.Rnd()) + 0) ’’產(chǎn)生的隨機(jī)數(shù)只能是5，不能再大了,再大的話，就要多用一個字節(jié)
     buff(i) = buff(i) Xor j
     k = buff(i) Mod Len(mstr)
     m = buff(i) \ Len(mstr)
     m = m * 2 ^ 3 + j
     temps = Mid(mstr, k + 1, 1) + Mid(mstr, m + 1, 1)
     Mid(outs, 2 * i + 1, 2) = temps
     Next
     encode = outs
    End Function
    Private Function decode(ByVal s As String) As String ’’解密
     On Error GoTo myERR
     Dim i As Long
     Dim j As Byte
     Dim k As Byte
     Dim m As Byte
     Dim mstr As String
     mstr = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789abcdefghijklmnopqrstuvwxyz"
     Dim t1 As String, t2 As String
     Dim buff() As Byte
     Dim n As Long
     n = 0
     For i = 1 To Len(s) Step 2
     t1 = Mid(s, i, 1)
     t2 = Mid(s, i + 1, 1)
     k = InStr(1, mstr, t1) - 1
     m = InStr(1, mstr, t2) - 1
     j = m \ 2 ^ 3
     m = m - j * 2 ^ 3
     ReDim Preserve buff(n)
     buff(n) = j * Len(mstr) + k
     buff(n) = buff(n) Xor m
     n = n + 1
     Next
     decode = StrConv(buff, vbUnicode)
     Exit Function
    myERR:
     decode = ""
    End Function