asterisk users - May 2006 - Can I recreate a Fax from a recorded file?

This is a very KGB / NSA / InterPOL / CIA type question, but if I have a
recorded file (G.711, no compression) can I feed it into standard in of
an application and have it recreate the fax that was send?

 

 

I don't know enough about the Fax handshaking to understand this.

 

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Interesting question!  If you have the audio in only (assuming it was a fax
received) or audio out only (assuming it was a fax sent), and you pair with
an identical fax machine to the original (assuming it responds exactly the
same in terms of handshakes, speeds, ECM, etc) then it might work.  I assume
you have a lot of time on your hands :)  
 
MD

  _____  

From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Alexander
Lopez
Sent: Wednesday, May 03, 2006 9:33 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: [Asterisk-Users] Can I recreate a Fax from a recorded file?



This is a very KGB / NSA / InterPOL / CIA type question, but if I have a
recorded file (G.711, no compression) can I feed it into standard in of an
application and have it recreate the fax that was send?

 

 

I don't know enough about the Fax handshaking to understand this.

 

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Maybe if you had the un-muxed sending side but I really have no idea. 
Interesting question though.

	-----Original Message----- 
	From: Alexander Lopez [mailto:Alex.Lopez@OpSys.com] 
	Sent: Wed 5/3/2006 9:32 AM 
	To: Asterisk Users Mailing List - Non-Commercial Discussion 
	Cc: 
	Subject: [Asterisk-Users] Can I recreate a Fax from a recorded file?
	
	

	This is a very KGB / NSA / InterPOL / CIA type question, but if I have a
recorded file (G.711, no compression) can I feed it into standard in of an
application and have it recreate the fax that was send?

	 

	 

	I don?t know enough about the Fax handshaking to understand this.

	 

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Alexander Lopez wrote:
> This is a very KGB / NSA / InterPOL / CIA type question, but if I have 
> a recorded file (G.711, no compression) can I feed it into standard in 
> of an application and have it recreate the fax that was send?
>
> I don?t know enough about the Fax handshaking to understand this.
>
In spandsp there is a program in the tests directory called fax_decode. 
It isn't very sophisticated, as it is intended for my test work, rather 
than general decoding. It is able to decode some FAX audio from a wave 
file, though.

There are some expensive commercial programs which do the job. Because 
FAX only sends one way at a time, the audio from the two directions is 
never jumbled up in recordings.

Steve

Acually, I have no time on my hands, but this was the thought while in
the shower this AM. Thought was the following. I needed to have one fax
sent to me and a customer at the same time. I know that I can recieve
and resend to both but I want to be able to 'snoop'.
 


________________________________

	From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Technical
Support
	Sent: Wednesday, May 03, 2006 9:57 AM
	To: 'Asterisk Users Mailing List - Non-Commercial Discussion'
	Subject: RE: [Asterisk-Users] Can I recreate a Fax from a
recorded file?
	
	
	Interesting question!  If you have the audio in only (assuming
it was a fax received) or audio out only (assuming it was a fax sent),
and you pair with an identical fax machine to the original (assuming it
responds exactly the same in terms of handshakes, speeds, ECM, etc) then
it might work.  I assume you have a lot of time on your hands :)  
	 
	MD

________________________________

	From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Alexander
Lopez
	Sent: Wednesday, May 03, 2006 9:33 AM
	To: Asterisk Users Mailing List - Non-Commercial Discussion
	Subject: [Asterisk-Users] Can I recreate a Fax from a recorded
file?
	
	

	This is a very KGB / NSA / InterPOL / CIA type question, but if
I have a recorded file (G.711, no compression) can I feed it into
standard in of an application and have it recreate the fax that was
send?

	 

	 

	I don't know enough about the Fax handshaking to understand
this.

	 

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You da' Man!!!

I'll try this.
 
>>In spandsp there is a program in the tests directory called 
>>fax_decode. 
>>It isn't very sophisticated, as it is intended for my test 
>>work, rather than general decoding. It is able to decode some 
>>FAX audio from a wave file, though.
>>
>>There are some expensive commercial programs which do the 
>>job. Because FAX only sends one way at a time, the audio from 
>>the two directions is never jumbled up in recordings.
>>
>>Steve

If you have both sides of the call it is possible.  It may not be practical 
though.  If one side was using spandsp then it is both possible and 
practical.

Craig

----- Original Message ----- 
From: "Steve Totaro" <stotaro@asteriskhelpdesk.com>
To: "Asterisk Users Mailing List - Non-Commercial Discussion" 
<asterisk-users@lists.digium.com>
Sent: Wednesday, May 03, 2006 11:02 PM
Subject: RE: [Asterisk-Users] Can I recreate a Fax from a recorded file?

> Maybe if you had the un-muxed sending side but I really have no idea. 
> Interesting question though.
>
> -----Original Message----- 
> From: Alexander Lopez [mailto:Alex.Lopez@OpSys.com]
> Sent: Wed 5/3/2006 9:32 AM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Cc:
> Subject: [Asterisk-Users] Can I recreate a Fax from a recorded file?
>
>
>
> This is a very KGB / NSA / InterPOL / CIA type question, but if I have a 
> recorded file (G.711, no compression) can I feed it into standard in of an 
> application and have it recreate the fax that was send?
>
>
>
>
>
> I don?t know enough about the Fax handshaking to understand this.
>
>
>
>

--------------------------------------------------------------------------------

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2006/5/4, Craig Guy <cguy@bigpond.net.au>:
>
> If you have both sides of the call it is possible.  It may not be
> practical
> though.  If one side was using spandsp then it is both possible and
> practical.
>
> Craig
>
> Could you elaborate ?
And if a fax is recorded with Asterisk voicemail application (in case an
error in fax detection occurred), would it still be possible and pratical ?
Regards
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<snip>
> This is a very KGB / NSA / InterPOL / CIA type
> question, but if I have a
> recorded file (G.711, no compression) can I feed it
> into standard in of
> an application and have it recreate the fax that was
> send?
</snip>
What is the specific reason as to why you want to
record it to a file and send it out. When you need to
send it to two people why not just send two faxes ?
What am I missing ?
Dovid

__________________________________________________
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I have a client that 'NEEDS' (his words not mine) to make sure that all
faxes, emails, calls, and mail are archived. Phone and email are simple,
Mail depends upon the integrity of the mail room, Faxes however can be
sent from anyone. They would like this as they recently had an issue
with a fax sent. Client claims that the fax received was NOT the Fax
sent. In the client file, the correct fax is there, but client attests
to a different copy. (Client is always right)

I know that I can use HylaFax and a custom context to grab the 'dialed'
number receive the fax via HylaFax and 're-send' it out again. But I
have not had the success rate I would like with HylaFax/IAXmodem. 

However, recording a file in Asterisk is a simple and manageable
concept. I do not expect problems with the recording load as there will
be less than 10 recordings at once. I will NOT be mixing them and will
be off-loading the tasks off to another machine after hours for
processing, realtime archiving is not needed.

They are also 'emotionally attached' to the rather large fax machines
(Mopier) that they have. (4)

They are a law firm that deals with rather large purchases, Planes,
Boats( SHIPS!!), small island countries, etc. etc,

They only have 3 attorneys and 3 para-legals, so they are difficult to
change in their ways, I find larger orgs are less resilient to change.

That's why......


> -----Original Message-----
> From: asterisk-users-bounces@lists.digium.com [mailto:asterisk-users-
> bounces@lists.digium.com] On Behalf Of Dovid Bender
> Sent: Thursday, May 04, 2006 9:06 AM
> To: Asterisk Users Mailing List - Non-Commercial Discussion
> Subject: Re: [Asterisk-Users] Can I recreate a Fax from a recorded
file?
> 
> <snip>
> > This is a very KGB / NSA / InterPOL / CIA type
> > question, but if I have a
> > recorded file (G.711, no compression) can I feed it
> > into standard in of
> > an application and have it recreate the fax that was
> > send?
> </snip>
> What is the specific reason as to why you want to
> record it to a file and send it out. When you need to
> send it to two people why not just send two faxes ?
> What am I missing ?
> Dovid
> 
> __________________________________________________
> Do You Yahoo!?
> Tired of spam?  Yahoo! Mail has the best spam protection around
> http://mail.yahoo.com
> _______________________________________________
> --Bandwidth and Colocation provided by Easynews.com --
> 
> Asterisk-Users mailing list
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users

>Why not capture the faxes (in or out) in tiff format, instead of audio
>format?  Setup your asterisk box to relay faxes!
I think in this case the impact on the client would be much greater if you
can show them a recreation of the image from the raw data; you could always
claim that a TIFF file was altered (which it can be, trivially) but it's
pretty much impossible to change the raw audio to your ends unless you are
in a Tom Clancy novel. I'm watching this thread closely because where I work
there's a lot of "he-said, she-said" over faxes too. If anyone can
work out
an example with SpanDSP, please share with the class!

>I would have no problem decoding a FAX, doctoring the images, then 
>creating modified audio from them. During decoding, the FAX modems 
>produce a channel estimate, so reproducing the characteristics of the 
>original audio path wouldn't be hard. I think it would be pretty easy to
>create fresh audio that no expert could dispute as possibly being the 
>original.
Ya, but...You Da Man. I mean doctoring fax audio so that mere mortals can
comprehend how to do it. I swear there's an i960 in your head so you can
listen to an audio stream and compose the TIFF in your mind. :-)>

>Why is this hard to fake at all?  You send a different fax to your
>system, and replace the Asterisk audio file with the one from the
>altered fax.  Additionally, the client has no realistic way of
>verifying the correctness of your audio-to-fax translation tool; it
>could just as easily output a TIFF file completely different from the
>one that was actually faxed.
That's interesting, I hadn't thought of it that way. I was thinking in
terms
of subtly modifying the original audio stream not outright replacing the
recording and faking the datestamp! Given that, essentially recording the
audio is the *same* as retaining the TIFF in terms of integrity
vulnerability. 

How about this: (theoretical of course)

1. Fax comes in
2. Audio is recorded
3. A checksum of the audio is generated then relayed somehow to a seperate,
secure system
4. In the event of a dispute, the checksum is retrieved, compared with the
original audio file, then the original audio is "replayed" and the fax
is
regenerated.

The 3. part I leave as an exercise for the reader.

Sounds like a potential business opportunity. Someone could setup a fax
proxy service that provides this sort of digital signing / archiving.
The originator could simply dial a toll-free access number, receive a
2nd dialtone and then dial the destination. Meanwhile the proxy is
recording the call, then decoding and allowing the archives to be viewed
online along with all relevent call details.

Hmm... Interesting.

Josh McAllister

-----Original Message-----
From: asterisk-users-bounces@lists.digium.com
[mailto:asterisk-users-bounces@lists.digium.com] On Behalf Of Colin
Anderson
Sent: Thursday, May 04, 2006 1:12 PM
To: 'Asterisk Users Mailing List - Non-Commercial Discussion'
Subject: RE: [Asterisk-Users] Can I recreate a Fax from a recorded file?
>Why is this hard to fake at all?  You send a different fax to your 
>system, and replace the Asterisk audio file with the one from the 
>altered fax.  Additionally, the client has no realistic way of 
>verifying the correctness of your audio-to-fax translation tool; it 
>could just as easily output a TIFF file completely different from the 
>one that was actually faxed.
That's interesting, I hadn't thought of it that way. I was thinking in
terms of subtly modifying the original audio stream not outright
replacing the recording and faking the datestamp! Given that,
essentially recording the audio is the *same* as retaining the TIFF in
terms of integrity vulnerability. 

How about this: (theoretical of course)

1. Fax comes in
2. Audio is recorded
3. A checksum of the audio is generated then relayed somehow to a
seperate, secure system 4. In the event of a dispute, the checksum is
retrieved, compared with the original audio file, then the original
audio is "replayed" and the fax is regenerated.

The 3. part I leave as an exercise for the reader.
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