End to End Cell Phone Encryption?

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Does anyone make a black box that could be attached into the headphone jack
of each end of a cell phone conversation and used to encrypt the call?   The
black box would then have a jack that goes to a normal headset.

I have seen such things for regular analog phone lines, but never as an
add-on for a cell phone.

--  
W



Re: End to End Cell Phone Encryption?
I'm looking for it too. I did some research on this topic, but I found only some app for smartphone to encrypt the call (e.g. SilentCircle). No headphones to encrypt....it's really incredible....have you some news?
On Friday, May 10, 2013 4:48:15 PM UTC+2, W wrote:
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Re: End to End Cell Phone Encryption?
On 8/14/2013 11:38 AM, andrea.zerbini8@gmail.com wrote:
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You wouldn't find it on the headphone jack.  A cell phone transmits
voice heavily compressed already.  Handset encryption is either really,
really weak or it turns the voice into an encrypted modem stream.  And a
modem won't go through a compressed-voice stream.  So you have to do the  
encryption in the voice-carrying data stream on the cell phone (e.g.,  
silentcircle).


Re: End to End Cell Phone Encryption?
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Can you expand on why encryption is not possible for a cell phone in the
handset?

The problem is there are many commercial applications that can be secretly
installed onto a cell phone that basically turn it into a spying base
station for a remote listener.   That person can listen in on your calls or
remotely activate the phone.   To the extent that the malware lives on the
phone, phone-based encryption isn't guaranteed to protect the call from
interception.

--  
W



Re: End to End Cell Phone Encryption?
On 9/8/2013 9:03 PM, W wrote:
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A headphone/handset is merely an audio input device.  On a cell phone,  
the audio is compressed nine ways to hell in order to minimize  
bandwidth, so that the network can spend more of its bits carrying cat  
videos.  The compression is based on passing across the network the  
minimum amount of information needed to create a mostly, though not  
perfectly, intelligible stream of English words, with the speaker's  
vocal nuances partially, but not completely, lost.

SO how do you encrypt that?  Since it's looking for the specific  
features of human voice, in order to compress them, it won't work right  
on almost anything else.

Thus cell phone encryption has to be done around the voice compressor.  
Either it takes the compressed voice and encrypts that data stream  
(which the phone already does, but the network has the key, so it's not  
private) or it takes the uncompressed voice and compresses and encrypts  
it, typically sending that over the network as data (i.e., disguised as  
a cat video).


Re: End to End Cell Phone Encryption?
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I'm not trying to encrypt the digitized form of the information.   But would  
there be some way to have hardware encryption of the analog signal in a  
wire-attached headset, based on some long code dialed into the headset.   As  
long as the person on the receiving end has same product and the same code  
dialed in, the reverse encryption should be straightforward.

--  
W  



Re: End to End Cell Phone Encryption?

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As an earlier poster mentione (might even have been you) there
were regular looking handsets that plugged into your standard
Bell 2500 set or equivalent... that could toggle between "clear"
and "encrypted". I used one myself 20 years ago when I was
in an office environment where calls were routinely taped.

I don't recall the specific method it used, by my guess
it was a rolling code frequency inversion. That is, the
voice part of the call was split into (for illustration here),
twenty separate frequency notches, and the part of speech that
was normally 250 to 500 hz was moved to 3000 to 3250, with
the others swapped around as well .

The main problem with this tech on a cellphone is:

  there is so much compresion, make that _lossy_ compression,
  going on in the cell system that anything not "looking like"
  (so to speak) key parts of the voice stream are lost by
  the codec. This would be devastating for getting the conversation
  across to you.

As a very bad analogy, if I say the numbers "1 2 3 [dropout] 5 6",
you'll process that to include the number "4". However, if I
said "3 6 2 [dropout] 1 5", you'd be lost.

The some would happen with the reconstructed (at your friend's
handset) stream. The parts that the cellco loses, which normaly
are filled in ok by your brain (well, to the extent that people
manage to delude themselves...) would be way out of the usual
sequence so the results would be pretty marginal.

That being said I'd love someone to at least try
to design something and test it out...


--  
_____________________________________________________
Knowledge may be power, but communications is the key
             dannyb@panix.com  
[to foil spammers, my address has been double rot-13 encoded]

Re: End to End Cell Phone Encryption?
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would
As
code

Very succinct and it makes clear why the approach I suggest might not work.

What about the same idea with a bluetooth headset, but the encryption has to
take place in the headset before any data is passed digitally to the phone?
So you would dial in an encryption code on both ends of the conversation,
and the headset would do hardware based encryption of the data before
sending anything to phone.

--  
W



Re: End to End Cell Phone Encryption?

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Same issue. I'd love to see someone try it, but to repeat a couple
of my earlier paragraphs:

The codecs in use compress the data stream containing your voice, and
in doing so throw out lots of the info. They're designed in such
a way that your brain "fills in" the missing segments.

So as a bad analogy, if I was speaking to you (directly in a room)
and said "1, 2, 3, [very faint so you hear "something" but
it's unintelligible], 5, 6", you'll automatically, without
thinking, fill in that as a "4".

Same concept applies to the lost compressive codecs.

But if I (in that room) said "2, 5, [very faint...], 3, 6, 1",
you wouldn't fill in the missing digit. And the same issue
would apply with standard codecs - they'll drop stuff that "looks"
like it's superfluous, but in reality critical.




--  
_____________________________________________________
Knowledge may be power, but communications is the key
             dannyb@panix.com  
[to foil spammers, my address has been double rot-13 encoded]

Re: End to End Cell Phone Encryption?
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work.
to
phone?
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So could you have the encryption hardware integrate with some custom written
CODEC in the phone?

Starts to sound like a very difficult project.

--
W



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