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rocksolid / Security / Re: How to shield your mobile phone ?

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* How to shield your mobile phone ?Guest
`* Re: How to shield your mobile phone ?Guest
 `* Re: How to shield your mobile phone ?Guest
  `* Re: How to shield your mobile phone ?Guest
   `* Re: How to shield your mobile phone ?Guest
    `- Re: How to shield your mobile phone ?Guest

1
Subject: How to shield your mobile phone ?
From: Guest
Newsgroups: rocksolid.shared.security
Organization: Dancing elephants
Date: Wed, 11 Apr 2018 16:37 UTC
Path: rocksolid2!.POSTED.10.128.12.155!not-for-mail
From: gue...@retrobbs.rocksolidbbs.com (Guest)
Newsgroups: rocksolid.shared.security
Subject: How to shield your mobile phone ?
Date: Wed, 11 Apr 2018 12:37:37 -0400
Organization: Dancing elephants
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Does somebody know howto securely shield ones mobile phone,
so that no connection to the gsm network is possible ?
The target is to do this without turning the phone off or
removing the battery.
I tried out a gizmo similar to this here:
http://www.faradaydefense.com/faraday-bags/70-cell-phone-black-pu-leather-x-large-privacy-protection-45-x-65-blackout-bag-.html
That seemed to work ok at first, but later turned out to be
not effective if the signal strength was very high (due to
proximity of the device to the base station). I need
something that will absolutely work, even if it means to
carry a solid metal case for the thing (I hope there is
something simpler).

What about tinfoil ? You can make nice hats out of it, would
it also help in this case ?

What about solid iron, or lead ?

If somebody has the knowledge about the physics, please
share.

Thanks

anon
Posted on: def3.i2p


Subject: Re: How to shield your mobile phone ?
From: Guest
Newsgroups: rocksolid.shared.security
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Date: Wed, 11 Apr 2018 17:40 UTC
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Subject: Re: How to shield your mobile phone ?
Date: Wed, 11 Apr 2018 13:40:45 -0400
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found this one here after some research. seems like really
tight aluminum foil should do the trick.

good read:
http://www.madsci.org/posts/archives/2002-03/1015162213.Eg.r.html


MadSci Network: Engineering
Query:
Re: Which materials block radio waves the most (and why)?
Date: Tue Feb 26 22:01:14 2002
Posted By: Adrian Popa, Director Emeritus, Hughes Research
Laboratories
Area of science: Engineering
ID: 1014075960.Eg Message:



Greetings:

Your project sounds very interesting. I have an experiment
that you
might perform to demonstrate the attenuation (the scientific
word for
blocking) of radio waves.

Radio Frequency

Radio waves are electromagnetic waves and travel at the
speed of light
which is 186, 280 miles per second (983,558,400 feet per
second). The
voltage in a radio wave alternates back and forth between
plus and minus
many times per second and we call this the frequency of the
radio wave
in cycles per second. Scientists have named frequency Hertz
(abbreviated Hz) after Heinrich Hertz, a German scientist,
who succeeded
in transmitting the first radio waves across a room in 1888.
Thus when
you hear a radio wave has a frequency of one megahertz ( 1
MHz), it
means one million (1,000,000) cycles per second. This
frequency is
usually marked 10 or 100 on the middle of AM (amplitude
modulation)
radio dials.

A radio frequency of 100 megahertz (100 MHz) means 100
million
(100,000,000) cycles per second. This is usually marked 100
on the
middle of FM (frequency modulation) radio dials.

Radio Wavelength

To understand my answer to your question you must know the
wavelength at
the radio frequency.

Wavelength equals the speed of light divided by the
frequency.

For a frequency of 1 MHz in the AM radio band the wavelength
is:

Wavelength at 1 MHz = 983,558,400/1,000,000 = 983.5 feet

For a frequency of 100 MHz in the FM radio band the
wavelength is:

Wavelength at100 MHz = 983,558,400/100,000,000 = 9.84 feet =
118 inches.

Radio Wave Attenuation

There are two general types of matter (substances) in the
universe that
affect electromagnetic waves, conductors and insulators
which are called dielectrics by scientists. Most, but not
all,
conductors are metals, such as copper, aluminum, silver and
gold. However,
salt water is also a rather poor conductor! Most, but not
all, dielectrics
are non metals. Examples of dielectrics are paper, plastic,
Teflon, glass,
ceramic and dry wood. Pure water is a good dielectric
substance!

Reflection, Transmission and Absorption of Radio Waves

Light waves are also electromagnetic waves and I will use
them for
examples; however, not all materials behave the same way at
both light
frequencies and radio frequencies. For example cardboard is
transparent
to radio waves and is opaque (blocks) to light waves. Light
waves have a
frequency around 500 trillion cycles per second (500
terahertz or 500 THz).

When a radio wave hits a material some of the power is
reflected at the
surface and some of the power is transmitted into and
possibly through
the material. If the material is metal, almost all of the
radio power is
reflected within the first few atoms of the material. A
small amount of
power is absorbed by the silver atoms and converted to
heat.

Example: a silvered mirror reflects about 95 % of light
power and about
95% of radio power and absorbs about 5 % of light and radio
power.

If the material is a dielectric, some of the power is
reflected at the
surface and some of the power travels through the material

Example: Some light reflects from the surface of clear glass
and some light
travels through the glass. The same is true for clear glass
and radio waves.

As the radio wave travels through the dielectric material
some of the power
is absorbed generating heat and some of the power travels
through and comes
out of the other side.

Example: Light traveling through sun glasses has a few
percent reflected
at the surface and between 10% and 90% of the light power
absorbed in heating
inside the glass and a few percent of the power coms out the
other side. Depending on the absorbing material in the
glass, the same is true
for radio waves. However, the light absorbing material in
the glass is usually
different than radio wave absorbing material .

This power absorption in a dielectric is called the
Attenuation Coefficient
of the material. How much power travels through a dielectric
depends on
both the thickness of the material and its attenuation
coefficient.

Dielectrics such as cardboard, paper, clear glass, Teflon,
some plastics,
pure water and many building materials have low attenuation
coefficients
and radio waves reflect from them and also easily pass
through them.

Example: You can receive radio waves in most houses made of
brick, wood,
plaster, wall board, cement etc.. Buildings made of metal or
metal coated
glasses, or steel reinforced concrete, reflect most of the
radio energy
and you cannot receive radio signals inside of them.

Earth contains many different materials that absorb radio
waves and so you
do not receive radio waves inside of long tunnels. However,
some long tunnels
have wires placed through the tunnel to transmit radio
waves, so that
drivers and emergency vehicles can still hear their radios
while driving
through them.

Experiment Number 1

Now let me discuss metal wire grids such as screens, chicken
wire, chain
link fences etc. Grids are mostly space with a small amount
of wire in
them. What happens to radio waves that they hit a metal
grid? The answer
depends on the wavelength of the radio wave. If the holes in
the wire
mesh are greater than one tenth of a wavelength across, most
of the radio
power passes through them and a small amount is reflected.
If the holes
in the mesh are one hundredth of a wavelength across or
less. Most of the
radio power is reflected and almost zero is transmitted
through the grid.
At sizes of holes between 1/10 and 1/100 wavelength,
different amounts of
radio power are reflected and transmitted. When we work with
radio
transmitters and receivers in the laboratory we often work
inside of screened
rooms. This way we block out external radio signals and keep
in the radio
waves that we are working on. Thus we can have hot or cooled
air
circulating within the screen room to keep it comfortable
and to let the
heat generated by the radio equipment escape.

For 1 MHz AM radio 1/100 of a wave length is 118 inches
For 100MHz FM radio 1/100 of a wave length is 1.18 inches.

Experiment Setup:

Make 3 boxes or cylinders about 2 feet long and 2 feet wide,
one made of
chicken wire with very large holes, one made of copper or
aluminum screen
with small holes and one made of cardboard covered with
several layers of
aluminum foil with no holes in it. Place an AM/FM transistor
radio on a
wooden platform in the middle of each box and compare the
strength of
several strong and weak AM and FM radio stations in open air
with the
strength of the same stations inside the boxes.

Expected Results:

Because of the difference in wavelengths you should be able
to hear the FM
stations and weak or no AM signals inside the chicken wire
box.

The screen box will probably block most FM signals and all
AM stations by
reflection.

The foil box will block all AM & FM signals by reflection.

Experiment Number 2

You could also compare AM & FM signals in a cardboard
box, a wooden box and perhaps a glass box (fish tank with a
metal lid). The
AM and FM radio signals strength should be the same inside
and outside of
the boxes. You should not be able to receive radio signals
inside of
an aluminum foil covered box.

NOTE: Radio waves are very sneaky and can get through the
smallest slits
in metal boxes so be sure that you overlap all openings very
well or make
a double layer covering the seams of the boxes. Also the
radios must be
battery powered for radio waves can come into the boxes
along the power
cable.

Good luck with your project.
Your Mad Scientist
Adrian Popa

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Posted on: def2.i2p


Subject: Re: How to shield your mobile phone ?
From: Guest
Newsgroups: rocksolid.shared.security
Organization: Dancing elephants
Date: Wed, 11 Apr 2018 17:51 UTC
References: 1
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From: gue...@retrobbs.rocksolidbbs.com (Guest)
Newsgroups: rocksolid.shared.security
Subject: Re: How to shield your mobile phone ?
Date: Wed, 11 Apr 2018 13:51:24 -0400
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nice graph of the frequencies involved:

http://scipp.ucsc.edu/~haber/ph5B/electromagnetic_spectrum.png
Posted on: def2.i2p


Subject: Re: How to shield your mobile phone ?
From: Guest
Newsgroups: rocksolid.shared.security
Organization: Dancing elephants
Date: Fri, 13 Apr 2018 20:17 UTC
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Subject: Re: How to shield your mobile phone ?
Date: Fri, 13 Apr 2018 16:17:23 -0400
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did some trials now with aluminumfoil, which seems to work
well. question is how to measure this correctly, maybe there is an
app for this...
Posted on: def2.i2p


Subject: Re: How to shield your mobile phone ?
From: Guest
Newsgroups: rocksolid.shared.security
Organization: RetroBBS II
Date: Fri, 20 Apr 2018 08:57 UTC
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From: gue...@retrobbs.rocksolidbbs.com (Guest)
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Subject: Re: How to shield your mobile phone ?
Date: Fri, 20 Apr 2018 08:57:20 +0000
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did some empirical testing now, and the only working
solution i found is to wrap the mobilephone tightly in 4
layers of aluminumfoil, and than to put that whole thing
into the faraday bag. with this setup the phone was not
connecting anywhere. anything less than that and short
connections and connection attempts could be seen (driving
around in the car).
after reading a lot on the stuff, it seems to me that
shielding has two crucial parameters:
1) tightness of the seal: there must be no gap anywhere, not
above 0,01 mm. this can with practical means only be
achieved by overlapping materials.
2) layer thickness: a limited amount of the waves will still
travel through thin layers. 0,5 mm seems to be the minimum
to shield my phone completely (samsung galaxy).


Posted on RetroBBS II


Subject: Re: How to shield your mobile phone ?
From: Guest
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Date: Thu, 26 Apr 2018 23:22 UTC
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Subject: Re: How to shield your mobile phone ?
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traveled over several international borders now with this
setup, and it seems to work well, no connections.
tightness is the key: just a very small opening (like below
1mm) and the darn thing connects. wrap it tight and it will
work.

after some cycles of wrapping and unwrapping the aluminum
foil little holes start to show around the lines of the
folding. so this no permanent solution, but must be renewed
every so often.
Posted on RetroBBS II


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