RC4

Function fRunRC4(sMessage, strKey) As String Dim kLen, x, y, i, j, temp Dim s(256), k(256)

'Init keystream
kLen = Len(strKey)
For i = 0 To 255
    s(i) = i
    k(i) = Asc(Mid(strKey, (i Mod kLen) + 1, 1))
Next
j = 0
For i = 0 To 255
    j = (j + k(i) + s(i)) Mod 255
    temp = s(i)
    s(i) = s(j)
    s(j) = temp
Next
'Drop n bytes from keystream
x = 0
y = 0
For i = 1 To 3072
    x = (x + 1) Mod 255
    y = (y + s(x)) Mod 255
    temp = s(x)
    s(x) = s(y)
    s(y) = temp
Next
'Encode/Decode
For i = 1 To Len(sMessage)
    x = (x + 1) Mod 255
    y = (y + s(x)) Mod 255
    temp = s(x)
    s(x) = s(y)
    s(y) = temp
    fRunRC4 = fRunRC4 & Chr(s((s(x) + s(y)) Mod 255) Xor Asc(Mid(sMessage, i, 1)))
Next

End Function