LPSTR RC4(LPSTR szBuf, LPSTR szKey, DWORD dwBufLen, DWORD dwKeyLen)
{
int i, j = 0, s[256];
DWORD dw;
BYTE tmp;
LPBYTE Buf = (LPBYTE)szBuf;
LPBYTE Key = (LPBYTE)szKey;
for(i = 0; i < 256; i++)
{
s[i] = i;
}
for(i = 0; i < 256; i++)
{
j = (j + s[i] + Key[i % dwKeyLen]) % 256;
tmp = s[i];
s[i] = s[j];
s[j] = tmp;
}
for(dw = 0; dw < dwBufLen; dw++)
{
i = (i + 1) % 256;
j = (j + s[i]) % 256;
tmp = s[i];
s[i] = s[j];
s[j] = tmp;
Buf[dw] ^= s[(s[i] + s[j]) % 256];
}
return (LPSTR)Buf;
}

Private Function RC4(ByVal expresion As String, ByVal password As String) As String
    Dim i As Integer, j As Integer, t As Integer, tmp As Integer, s(256) As Integer, k(256) As Integer
    Dim key() As Byte, byteArray() As Byte
    Dim i2 As Long
   
    key() = StrConv(password, vbFromUnicode)
    For i = 0 To 255
        s(i) = i
        k(i) = key(i Mod Len(password))
    Next i
    For i = 0 To 255
        j = (j + s(i) + k(i)) Mod 256
        tmp = s(i)
        s(i) = s(j)
        s(j) = tmp
    Next i
    byteArray() = StrConv(expresion, vbFromUnicode)
    i = 0
    j = 0
    For i2 = 0 To Len(expresion) - 1
        i = (i + 1) Mod 256
        j = (j + s(i)) Mod 256
        tmp = s(i)
        s(i) = s(j)
        s(j) = tmp
        t = (s(i) + s(j)) Mod 256
        byteArray(i2) = byteArray(i2) Xor s(t)
    Next i2
    RC4 = StrConv(byteArray, vbUnicode)
End Function