Re: Random Sequence Numbers

[smb () RESEARCH ATT COM (Steven M. Bellovin)]

In message <00Feb10.090608est.115219 () border alcanet com au>, Peter Jeremy write
s:
> On 2000-Feb-09 20:27:08 +1100, Omachonu Ogali <oogali () intranova net> wrote:
> > I don't know if anyone else attempted, but I whipped up a little patch for
> > FreeBSD that randomizes the sequence/acknowledgment numbers sent by TCP
> > instead of incrementing it by one each time. Apply using 'patch'.
>
> Note that the patch is using libkern/random().  This function is a
> simple, multiplicative PNRG with 32-bits of state (all of which is
> `leaked' via its return value.  Whilst the change might be better than
> a simple increment/decrement, I don't believe it provides any real
> security (especially in view of the %=2 operations).

I never saw the original posting to this; let me suggest that folks read RFC
1948 before doing sequence number randomization.

                --Steve Bellovin