Modem datatapping/sniffing

Can anyone help me in the way of datatapping/sniffing a dial-up modem
connection by only access to the complex signals carries in the 2-wire
link(listening to the voice)?
For this purpose it should be to separate the incoming and outgoing
signals in full-duplex mode, then demodulating them according to the
standard of connection. The most public standard is V.34 uses QAM
modulation. Now:
-Is it possible to separate the signals in each direction in full-duplex
mode by hardware or bye any software way?
-Is there any way after separating the signals to demodulating
them(especially in QAM) completely?

Thanks all

hamid_brj wrote:

> Can anyone help me in the way of datatapping/sniffing a dial-up modem
> connection by only access to the complex signals carries in the 2-wire
> link(listening to the voice)?

For the modern protocols this is not feasible. You have to cut in 
between the modems. Even if you can separate the sides of the link, the 
sniffed data is likely to be unreliable. The only practical method is 
man-in-the-middle.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com

Vladimir Vassilevsky wrote:
> 
> 
> hamid_brj wrote:
> 
>> Can anyone help me in the way of datatapping/sniffing a dial-up modem
>> connection by only access to the complex signals carries in the 2-wire
>> link(listening to the voice)?
> 
> 
> For the modern protocols this is not feasible. You have to cut in 
> between the modems. Even if you can separate the sides of the link, the 
> sniffed data is likely to be unreliable. The only practical method is 
> man-in-the-middle.

To elaborate, if the modem uses echo cancellation you won't be able to 
decode things by sniffing. If it doesn't use echo cancellation you will 
be able to decode by sniffing. This pretty much limits you to V.22bis or 
below for full duplex modems. Most FAX modems work in ping-pong mode, so 
you can decode those.

Regards,
Steve

hamid_brj wrote:
> Can anyone help me in the way of datatapping/sniffing a dial-up modem
> connection by only access to the complex signals carries in the 2-wire
> link(listening to the voice)?

There are no complex signals on two-wire links.

> For this purpose it should be to separate the incoming and outgoing
> signals in full-duplex mode,

Yes. You need a "hybrid" to do that, and to match the line impedances. 
That can't be done with a tap, but if you can cut the line and insert 
the proper equipment, the reconnected line should behave normally. For 
further details, consult NSA.

>                         then demodulating them according to the
> standard of connection. The most public standard is V.34 uses QAM
> modulation. Now:
> -Is it possible to separate the signals in each direction in full-duplex
> mode by hardware or bye any software way?
> -Is there any way after separating the signals to demodulating
> them(especially in QAM) completely?

Jerry
-- 
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������

hamid_brj wrote:
> Can anyone help me in the way of datatapping/sniffing a dial-up modem
> connection by only access to the complex signals carries in the 2-wire
> link(listening to the voice)?

Ever since it came out the GWB had the NSA perform wire taps without a 
warrant, I have noticed the number of questions related to telephony 
(and related) on comp.dsp has sky-rocketed.

DTMF, mu-law, call-progress, upsampling 8KHz audio, and now this.

Is it all a coincidence?

-- 
Jim Thomas            Principal Applications Engineer  Bittware, Inc
jthomas@bittware.com  http://www.bittware.com    (603) 226-0404 x536
When you're great, people often mistake candor for bragging. - Calvin

> below for full duplex modems. Most FAX modems work in ping-pong mode, so
> you can decode those.

Is any free soft to decode fax signals?

Regards,
Zbi

try
Spandsp - http://www.soft-switch.org/

please let me know if it really works

-Clark


"news.aster.pl" <zka@tenbit.pl> wrote in message
news:43ea6e90$0$1469$f69f905@mamut2.aster.pl...
> > below for full duplex modems. Most FAX modems work in ping-pong mode, so
> > you can decode those.
>
> Is any free soft to decode fax signals?
>
> Regards,
> Zbi
>
>

Can you spell

J-A-I-L  T-I-M-E   ?

Dirk

hamid_brj wrote:
> Can anyone help me in the way of datatapping/sniffing a dial-up modem
> connection by only access to the complex signals carries in the 2-wire
> link(listening to the voice)?
> For this purpose it should be to separate the incoming and outgoing
> signals in full-duplex mode, then demodulating them according to the
> standard of connection. The most public standard is V.34 uses QAM
> modulation. Now:
> -Is it possible to separate the signals in each direction in full-duplex
> mode by hardware or bye any software way?
> -Is there any way after separating the signals to demodulating
> them(especially in QAM) completely?
> 
> Thanks all

Dear Vladimir, Steve, Jerry, and others

Do you know any equipment to insert between the line to separate signal in
each direction and have no effect on the connection? Is it only a hybrid
and which hybrid or it should be in the form of man-in-the-middle?
Does tow-way telephone voice connection(includes dialup modem connections)
separate in PSTN centers using any hybrid, and if so, can we use the
equipment in this way?
Is there any available equipment in market or I should design it? Isn�t
there any software solution for this project at all?

Thanks in advance

Really hamid,

If this project is done for the wrong people it would be illegal in the
US.  So who are you and who are you doing it for?  My feeling is that
since you have to ask these questions here it can't be for anyone good.
Are you just curious or are you looking for co-conspirators?

Dirk

hamid_brj wrote:
> Dear Vladimir, Steve, Jerry, and others
>
> Do you know any equipment to insert between the line to separate signal in
> each direction and have no effect on the connection? Is it only a hybrid
> and which hybrid or it should be in the form of man-in-the-middle?
> Does tow-way telephone voice connection(includes dialup modem connections)
> separate in PSTN centers using any hybrid, and if so, can we use the
> equipment in this way?
> Is there any available equipment in market or I should design it? Isn't
> there any software solution for this project at all?
> 
> Thanks in advance