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Preventing Image Download - a possible solution?

P: n/a
Every so often, I see someone wanting to prevent heir images being
downloaded and the general consensus is "you can't".

Now a friend has asked me to think some more about this, and I think
that I might have a solution. It is somewhat complicated, but it
probably ought to work....

Forget disabling right click menus and the like, it seems to me that
the problem is screen capture.

To get around this, I consider the fact that the human eye is quite
versatile.

What if we dice the image into small sections and present these as a
table? The "trick" being, that we present each image in the
"checkerboard" of the table as an animated GIF - with each alternate
square toggling between part of the picture and a
black/white/transparent background?

Would that work? Would the human eye "fill in the gaps" and see a
single, complete picture?

I realise that it might not look perfect, but would it be "good
enough"?

Of course, when the algorithm is known, it could be reverse engineered,
but so can locks and you trust your house and car to them. Security
just has to be "good enough" to deter 99% of people, but can never be
totally watertight.

What do you think? Is this idea feasible? Has it already been done? Is
there any variation on it that can prevent a screen dump type image
capture?

Jan 3 '07 #1
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15 Replies


P: n/a
Rik
Baron Samedi wrote:
Every so often, I see someone wanting to prevent heir images being
downloaded and the general consensus is "you can't".
Indeed.
Now a friend has asked me to think some more about this, and I think
that I might have a solution. It is somewhat complicated, but it
probably ought to work....

Forget disabling right click menus and the like, it seems to me that
the problem is screen capture.

To get around this, I consider the fact that the human eye is quite
versatile.

What if we dice the image into small sections and present these as a
table? The "trick" being, that we present each image in the
"checkerboard" of the table as an animated GIF - with each alternate
square toggling between part of the picture and a
black/white/transparent background?

Would that work? Would the human eye "fill in the gaps" and see a
single, complete picture?
And have a terrible headache? I hardly think that many animated pictures
can keep up a 20Hz or more. And think of how it will behave when not all
images are in... On top of it all you cannot control wether they are in
sync or not, which can very well lead to very, very weird effects.
>
I realise that it might not look perfect, but would it be "good
enough"?
Not very likely. But hey, try it, slicing and animating something that
simple shouldn't take very long. A grotesque example culd be made in no
time.
Of course, when the algorithm is known, it could be reverse
engineered, but so can locks and you trust your house and car to
them. Security just has to be "good enough" to deter 99% of people,
but can never be totally watertight.

What do you think? Is this idea feasible? Has it already been done? Is
there any variation on it that can prevent a screen dump type image
capture?
I've seen weird overlays with random parts of pictures over each other.
Doesn't look very good loading, and after loading it's still a ugly.

As always, if you want to protect you material you shouldn't put it online.
If you want to show some art that people will have to pay for, put online
either a watermarked a low resolution picture (or both) online.
--
Rik Wasmus
Jan 3 '07 #2

P: n/a
Baron Samedi wrote:
>
What if we dice the image into small sections and present these as a
table?
Considering that each image is a separate request to the server (plus
all the added table markup bloat) download time could be severely impacted.

--
Berg
Jan 3 '07 #3

P: n/a
Baron Samedi <Pa************@gmail.comwrote:
Every so often, I see someone wanting to prevent heir images being
downloaded and the general consensus is "you can't".
You can do this. But the only way to do this is to keep this image on
your local harddisk and never show it on your web page.

There's no way to prevent that other people can download your image when
you put it on your web page. The problem is that the browser has to
download the image to be able to show it on the screen. So regardless of
what you're doing, the download has happend in all cases even before the
image is shown the very first time. So depending of the browser the
people are using, they may even be able to get your image from the
browser cache, or configure their browsers so that you're script to
block the right mouse click will be deactivated, or to disable GIF
animations etc. If someone wants to get your image, he is able to get
it.

So all you can do is

- not to show your image at all in the web
- only show a scaled down or low quality version of your image
so nobody is able to use the full quality image.

--
Alexander
Jan 3 '07 #4

P: n/a
Baron Samedi wrote:
Every so often, I see someone wanting to prevent heir images being
downloaded and the general consensus is "you can't".
Very often discussed, it remains "you can't".

Some options are:

1) don't publish images
2) restrict size and quality to e.g. 300 x 400 pixels,
to make high quality prints impossible
3) write a signature like 'www.mydomain.com' into the image,
to advertise at least your site
4) deliver another version of the image,
if the referrer is not from the own site.

I like a combination of 3) and 4), i.e. in case of a foreign referrer a
version with signature/copyright notice is delivered.

Helmut Wollmersdorfer
Jan 3 '07 #5

P: n/a

Rik wrote:
Baron Samedi wrote:
Every so often, I see someone wanting to prevent heir images being
downloaded and the general consensus is "you can't".

Indeed.
Now a friend has asked me to think some more about this, and I think
that I might have a solution. It is somewhat complicated, but it
probably ought to work....

Forget disabling right click menus and the like, it seems to me that
the problem is screen capture.

To get around this, I consider the fact that the human eye is quite
versatile.

What if we dice the image into small sections and present these as a
table? The "trick" being, that we present each image in the
"checkerboard" of the table as an animated GIF - with each alternate
square toggling between part of the picture and a
black/white/transparent background?

Would that work? Would the human eye "fill in the gaps" and see a
single, complete picture?

And have a terrible headache? I hardly think that many animated pictures
can keep up a 20Hz or more. And think of how it will behave when not all
images are in... On top of it all you cannot control wether they are in
sync or not, which can very well lead to very, very weird effects.
I am just a dumn non-techy, so I don't have the answers (which is why I
ask).

Isn't this how movies work? Lots of images, shown 25 per second,
folling the eye into thinking that it is seeing motion?

I am asking for a friend who wants to join an online dating site, but
is paranoid about putting her picture on the internet (let's not
discuss that, let's just keep to the techy stuff). I suggetsed that
she get a free site, like GeoCitites or soemthing, host the picture
there and give out the URL. But,. the problem is still how to prevent
screen dumps,e tc, and all taht I can think of is not showing the whole
image at once...

I realise that it might not look perfect, but would it be "good
enough"?

Not very likely. But hey, try it, slicing and animating something that
simple shouldn't take very long. A grotesque example culd be made in no
time.
Sorry, but I don't knwo how to.

Jan 5 '07 #6

P: n/a
>>>3) write a signature like 'www.mydomain.com' into the image,
to advertise at least your site

Yeah, do this and then hope people want to downlaod your image! Most
won't though....

Jan 5 '07 #7

P: n/a
On 2007-01-05, Baron Samedi <Pa************@gmail.comwrote:
[snip]
What if we dice the image into small sections and present these as a
table? The "trick" being, that we present each image in the
"checkerboard" of the table as an animated GIF - with each alternate
square toggling between part of the picture and a
black/white/transparent background?

Would that work? Would the human eye "fill in the gaps" and see a
single, complete picture?

And have a terrible headache? I hardly think that many animated pictures
can keep up a 20Hz or more. And think of how it will behave when not all
images are in... On top of it all you cannot control wether they are in
sync or not, which can very well lead to very, very weird effects.

I am just a dumn non-techy, so I don't have the answers (which is why I
ask).

Isn't this how movies work? Lots of images, shown 25 per second,
folling the eye into thinking that it is seeing motion?

I am asking for a friend who wants to join an online dating site, but
is paranoid about putting her picture on the internet (let's not
discuss that, let's just keep to the techy stuff). I suggetsed that
she get a free site, like GeoCitites or soemthing, host the picture
there and give out the URL. But,. the problem is still how to prevent
screen dumps,e tc, and all taht I can think of is not showing the whole
image at once...
Even if it did work, which it might, someone could easily take the
animated gif apart again (or merge its layers together) and reconstruct
the original image.
Jan 6 '07 #8

P: n/a

Ben C wrote:
On 2007-01-05, Baron Samedi <Pa************@gmail.comwrote:
[snip]
What if we dice the image into small sections and present these as a
table? The "trick" being, that we present each image in the
"checkerboard" of the table as an animated GIF - with each alternate
square toggling between part of the picture and a
black/white/transparent background?

Would that work? Would the human eye "fill in the gaps" and see a
single, complete picture?

And have a terrible headache? I hardly think that many animated pictures
can keep up a 20Hz or more. And think of how it will behave when not all
images are in... On top of it all you cannot control wether they are in
sync or not, which can very well lead to very, very weird effects.
I am just a dumn non-techy, so I don't have the answers (which is why I
ask).

Isn't this how movies work? Lots of images, shown 25 per second,
folling the eye into thinking that it is seeing motion?

I am asking for a friend who wants to join an online dating site, but
is paranoid about putting her picture on the internet (let's not
discuss that, let's just keep to the techy stuff). I suggetsed that
she get a free site, like GeoCitites or soemthing, host the picture
there and give out the URL. But,. the problem is still how to prevent
screen dumps,e tc, and all taht I can think of is not showing the whole
image at once...

Even if it did work, which it might, someone could easily take the
animated gif apart again (or merge its layers together) and reconstruct
the original image.
I disagree with the word "easilly".

Look, abossultely *no* security is foolproof. It just has to be "good
enough".

In this case, a recently single friend wants to get back into dating,
but she doesn't want to mail her photo to strangers (at least
initially) - all that I could think of was to host it somewhere, give
them a UTL and point them to it.

I didn't want to go into this before, because, UseNet being what it is,
the thread will probably now spin of on tangents about whether she
should be meeting strangers on the net, and if she doesn't trust them
with her pic (remember, I said *initially*, after she meets them, she
may want to share her pic, but not until she knows them) then she
shouldn't be meeting them, etc, etc.

Can we please stick to the technical aspect on this one? It is quite an
interesting technical challenge.

Jan 8 '07 #9

P: n/a
Baron Samedi wrote:
>
Isn't this how movies work? Lots of images, shown 25 per second,
folling the eye into thinking that it is seeing motion?
Since the goal was to display a *still* picture, how the eye can be
tricked into seeing motion isn't relevant.
>
I am asking for a friend who wants to join an online dating site, but
is paranoid about putting her picture on the internet (let's not
discuss that, let's just keep to the techy stuff). I suggetsed that
she get a free site, like GeoCitites or soemthing, host the picture
there and give out the URL. But,. the problem is still how to prevent
screen dumps,e tc, and all taht I can think of is not showing the whole
image at once...
Whatever code would be used to make this happen, can be copied and used
elsewhere.
Jan 8 '07 #10

P: n/a

Harlan Messinger wrote:
Baron Samedi wrote:

Isn't this how movies work? Lots of images, shown 25 per second,
folling the eye into thinking that it is seeing motion?

Since the goal was to display a *still* picture, how the eye can be
tricked into seeing motion isn't relevant.
The first time in my life that I ever saw a video camera - back in
1989, no less - it was being used to film a cactus in a botanical
garden!

If it achieves the purpose, let someone have a look at something, does
it matter how it is done? I wouldn't advocate a standard movie format,
like mpeg, because that is too easy to capture, but even just two still
images, each showing only 50%, alternated quickly ought to be good
enough to let the eye think that it is seeing a single, motionless
picture.

Maybe we are talking at crossed porpoises here? Why should some moving
format be used to represent a motionless object?



I am asking for a friend who wants to join an online dating site, but
is paranoid about putting her picture on the internet (let's not
discuss that, let's just keep to the techy stuff). I suggetsed that
she get a free site, like GeoCitites or soemthing, host the picture
there and give out the URL. But,. the problem is still how to prevent
screen dumps,e tc, and all taht I can think of is not showing the whole
image at once...

Whatever code would be used to make this happen, can be copied and used
elsewhere.

As previously stated - there is *no* absolute security, anywhere. Not
the locks on your house, not even the locks on the Whitehouse - about
10 or 15 years ago a slightly deranged guy climbed the walls of
Buckingham Palace and found the Queen's bedroom. He sat on the end of
her ed chatting until help (summoned by her silent alarm button)
arrived.

There is no absolute security, and I don't want to pretend that there
is. TO paraphrase Bruce Schneier, security just needs to be good enough
to protect whatever you want to protect. You don't put a 20k alarm
system on a 5k car.

So, just enough to dissuade the average internet user, pelase.

Jan 8 '07 #11

P: n/a
On 2007-01-08, Baron Samedi <Pa************@gmail.comwrote:
>
Ben C wrote:
[snip]
>Even if it did work, which it might, someone could easily take the
animated gif apart again (or merge its layers together) and reconstruct
the original image.

I disagree with the word "easilly".
It's a matter of degree. How easily? Well I think you could do it in a
few button clicks with a program like the GIMP or Photoshop. It would
require some computer literacy, but not much more than that.
Look, abossultely *no* security is foolproof. It just has to be "good
enough".
No problem then, I just didn't want you to you think your solution was
more foolproof than it was.
Jan 8 '07 #12

P: n/a

Baron Samedi wrote:
[...]
So, just enough to dissuade the average internet user, pelase.
There is *no way* to protect the image once it is posted. None, zero,
zip. If protection only has to be "good enough", use Flickr knowing
that anyone who wants to will get the image, but will have to jump
through a few hoops to do it.

I'd suggest that the "average" internet user has absolutely no interest
whatsoever in your friend. They may wish to save her image, but so
what? What personal security issue does that raise? If anyone is
determined to use her image for foul play (however you wish to define
that), they will. Your *only* security is to not post the image.

But what "security" does not posting the image provide? People are
mugged, murdered, raped and assaulted on a fairly regular basis in all
parts of the world without ever having posted their image on the
internet. I don't think posting an image increases her likelihood of
being a victim of such crimes (or whatever else she is afraid of);
similarly, not posting it is no security that it won't happen.

--
Rob

Jan 10 '07 #13

P: n/a
Baron Samedi wrote:
Harlan Messinger wrote:
>Baron Samedi wrote:
>>Isn't this how movies work? Lots of images, shown 25 per second,
folling the eye into thinking that it is seeing motion?
Since the goal was to display a *still* picture, how the eye can be
tricked into seeing motion isn't relevant.

If it achieves the purpose, let someone have a look at something, does
it matter how it is done?
It has nothing to do with whether it matters how it's done. You were
suggesting that displaying this still picture using a rapidly changing
mosaic of smaller images should work because of the way motion pictures
work. The way motion pictures work is one thing, and the solution you
were talking about is a completely different thing that has nothing to
do with the way motion pictures work, so I was pointing out to you that
your idea that one would work *because* the other works doesn't make sense.
Jan 10 '07 #14

P: n/a

RobG wrote:
Baron Samedi wrote:
[...]
So, just enough to dissuade the average internet user, pelase.

There is *no way* to protect the image once it is posted. None, zero,
zip. If protection only has to be "good enough", use Flickr knowing
that anyone who wants to will get the image, but will have to jump
through a few hoops to do it.

I'd suggest that the "average" internet user has absolutely no interest
whatsoever in your friend. They may wish to save her image, but so
what? What personal security issue does that raise? If anyone is
determined to use her image for foul play (however you wish to define
that), they will. Your *only* security is to not post the image.

But what "security" does not posting the image provide? People are
mugged, murdered, raped and assaulted on a fairly regular basis in all
parts of the world without ever having posted their image on the
internet. I don't think posting an image increases her likelihood of
being a victim of such crimes (or whatever else she is afraid of);
similarly, not posting it is no security that it won't happen.

--
Rob

Good points, Rob, and I tend to agree. However, it's not my wishes we
are talking of here. "Mine is not to reason why ..."

Jan 23 '07 #15

P: n/a

Harlan Messinger wrote:
Baron Samedi wrote:
Harlan Messinger wrote:
Baron Samedi wrote:
Isn't this how movies work? Lots of images, shown 25 per second,
folling the eye into thinking that it is seeing motion?
Since the goal was to display a *still* picture, how the eye can be
tricked into seeing motion isn't relevant.
If it achieves the purpose, let someone have a look at something, does
it matter how it is done?

It has nothing to do with whether it matters how it's done. You were
suggesting that displaying this still picture using a rapidly changing
mosaic of smaller images should work because of the way motion pictures
work. The way motion pictures work is one thing, and the solution you
were talking about is a completely different thing that has nothing to
do with the way motion pictures work, so I was pointing out to you that
your idea that one would work *because* the other works doesn't make sense.
Ok, so I am dumb. Why wouldn't it work? Or, to pharse it another way,
can you see how to make it work.

Again, it doesn't have to be toally unbreakable. Just too much effort
for *the average user* to attempt to break it. And image quality
doesn't have to be perfect, just good nough to be recongnizable.

Jan 23 '07 #16

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