On Wed, 29 Jul 2026 22:22:37 -0700, Maria Sophia wrote:

Having never used Python Pillow, and while I was already writing
code, I decided to try to use it to foil camera sensor PRNU
fingerprinting.

This was the first I had heard of such a thing, so I looked it up <https://en.wikipedia.org/wiki/Photo_response_non-uniformity>.

That?s just an artifact of the way image sensors are made, so it?s not deliberately designed to be a secret identification feature or
anything; the article even says that it is possible to characterize
the noise pattern for a given sensor, and subtract it out to produce higher-quality images, e.g. for metrology purposes.

--- PyGate Linux v1.5.19
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On Thu, 30 Jul 2026 07:42:33 -0800, Maria Sophia wrote:

With respect to the Pillow imaging tools, the part I'm experimenting
with is how best to easily break that PRNU fingerprint with image manipulation.

You mean in the general case, for an image obtained from an unknown
camera?

Because if you only want to do it for your own camera(s), you can do
what the Wikipedia article describes, and use a calibration image to
determine the sensor ?fingerprint?, so you can subtract that from all
images you intend to publish.

--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On 30/07/2026 17.42, Maria Sophia wrote:
[...]

Right now, the PRNU-scrubbing script pipeline is running two full
destructive passes, each intended to disrupt PRNU by performing
a. blur
b. rotate
c. crop
d. resize
e. inject noise
But that doubly scrubbed image is a bit to destroyed to be usable.

Have you tried to de-noise first, with
something like BM3D, and then re-noise?

For both operations likely some noise
parameter is required.

I know this is not the same as the PRNU,
but de-noising will reduce / remove any
uncorrelated information.

Re-noise will make it plausible.

bye,

--

piergiorgio

--- PyGate Linux v1.5.19
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On Fri, 31 Jul 2026 13:59:58 -0800, Maria Sophia wrote:

... but PRNU isn't random noise.

It is random noise, but only in the spatial domain; it is not
time-varying.

--- PyGate Linux v1.5.19
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On 01/08/2026 01.13, Maria Sophia wrote:
[...]

I'm under the impression there is some
confusion here.

De-noising algorithms, like BM3D or any
de-noising auto-encoder, de-noise just
one image.
There is no temporal noise involved, it
is only spatial, since the algorithms
see only one, single, image.

There are temporal de-noising algorithm
which could be applied to video sequences,
but this does not seem to be the case here.

On the other hand, PRNU will have some
spatial statistical properties, even if
it is fixed for a given sensor.

Now, assuming we have some PRNU from some
unrelated sensor (meaning we can generate
a spatial noise with same statistical
properties), it would be possible to
consider to apply this noise ("apply", not
"add") to a given image.

This means the effective PRNU will be the
combination ("combination", not "sum") of
two PRNUs, resulting in a new fingerprint,
different from the original one.

So, de-noising is not really needed, but it
might be helpful to reduce / remove / modify
the original PRNU, so that the applied one
will be more evident.

The point here is that the image content
will not be altered too much, so quality
will be somehow preserved.
Different than blurring or resizing.

If you do not like BM3D, you can look, as
mentioned above, into de-noising auto-encoders.
These will be even more aggressive in removing
the PRNU content (maybe with more damage to
the overall image).

Finally, consider the "simple" case of generative
algorithm (AI stuff, so to speak).
These could (YMMV) generate image *without* any
PRNU, similar or identical to the one taken
with the camera.
So, the fingerprint will be gone (maybe there will
be another one from the AI).

It seems to me there is a lot to explore way
beyond the simple image modification algorithms.

bye,

--

piergiorgio

--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Piergiorgio Sartor <piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> wrote:

On 01/08/2026 01.13, Maria Sophia wrote:
[...]

I'm under the impression there is some
confusion here.

To be expected considering who the OP is...

On the other hand, PRNU will have some
spatial statistical properties, even if
it is fixed for a given sensor.

Now, assuming we have some PRNU from some
unrelated sensor (meaning we can generate
a spatial noise with same statistical
properties), it would be possible to
consider to apply this noise ("apply", not
"add") to a given image.

This means the effective PRNU will be the
combination ("combination", not "sum") of
two PRNUs, resulting in a new fingerprint,
different from the original one.

So, de-noising is not really needed, but it
might be helpful to reduce / remove / modify
the original PRNU, so that the applied one
will be more evident.

The two main issues regarding PRNU that the OP has missed when jumping to conclusions are: 1) it is probabilitic, 2) it is comparative.

That means for 1) there's no guarantee that the noise in your camera
sensor is unique to you. It might be common, or very similar, to all
cameras of that model and batch. The statistical model is based on small samples of camera sensors so it isn't a globally accurate model.

For 2) that means it cannot state which device was used to take a photo
without having the device in question in your possession.

Just like ballistics. Once you have a suspect gun in your possession you
can make some assessment of the probability of whether that gun fired a particular round.


--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

On Sun, 2 Aug 2026 11:18:31 -0800, Maria Sophia wrote:

I'm curious, Chris, why you always feel so desperate to try to
insult me?

Just killfile the haters and move on.

--- PyGate Linux v1.5.19
* Origin: Dragon's Lair, PyGate NNTP<>Fido Gate (3:633/10)

Maria Sophia <mariasophia@comprehension.com> wrote:

Chris wrote:

I'm under the impression there is some
confusion here.

To be expected considering who the OP is...

I'm curious, Chris, why you always feel so desperate to try to insult me?

As you've argued before that calling someone stupid is not an insult if
it's true. I'm not insulting you...

I also gave you a lot of useful information which you've chosen to ignore.

And then you lie when you say you don't know of another way to share python code. You've been informed many times how to share code usefully.

Posting code on usenet when it's python is particularly bad as all tabs are lost and therefore the script will not work. Attempts at fixing the
indentation may make the code run, but probably incorrectly.


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