LSB mode will crash when use PNG with transparent backgound
liam-thunder opened this issue · comments
when I try to decode some PNG with transparent backgound, my Chrome or IE will stuck and crash..
1. Check if your bug can be reproduced in stego.js.org
2. If yes, attach your PNG and messages here. I’ll take a look when I have
time.
3. If no, take a look at the difference at the calling method. You might
did something wrong.
…On Wed, May 16, 2018 at 6:13 AM ChenYou ***@***.***> wrote:
when I try to encode some PNG with transparent backgound, my Chrome or IE
will stuck and crash..
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@zeruniverse thanks for your quick reply!
I've tested on stego.js.org, using a png with transparent background a simple message "1", using Level 1 to write image
Write can be performed successfully, but the picture's background has been turned into all black. And this black-background png image's message can be read successfully.
But when I read message from a transparent background png image with no message contained, it will caused my Chrome stuck and crash.
BTW, when I try to read some message from a picture (with background) which has no message contained, it will show some messy characters. I don't know the algorithm behind stego, but I wonder if there any possible enhancement to make this behavior better?
Thanks!
1. You need level 0 for LSB.
2. The algorithm was designed in the way that you can always extract
messages, but with incorrect key, the message is wrong. This is intended
such that people don’t know whether it’s something inside the image if they
don’t know the password. The crash is due to the same reason (You are
decrypting something meaningless) and again it’s intended
…On Wed, May 16, 2018 at 6:54 PM ChenYou ***@***.***> wrote:
@zeruniverse <https://github.com/zeruniverse> thanks for your quick reply!
I've tested on stego.js.org, using a png with transparent background a
simple message "1", using Level 1 to write image
[image: star_png1580]
<https://user-images.githubusercontent.com/1531217/40152231-fc316040-59b6-11e8-82f1-3ac898d72d4f.png>
Write can be performed successfully, but the picture's background has been
turned into *all black*. And this black-background png image's message *can
be read successfully*.
But when I read message from a transparent background png image *with no
message contained*, it will caused my Chrome *stuck and crash*.
BTW, when I try to read some message from a picture (*with background*)
which has no message contained, it will show some messy characters. I don't
know the algorithm behind stego, but I wonder if there any possible
enhancement to make this behavior better?
Thanks!
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To get better behaviour, you can append some verification bits everytime
you wrote message and check those bits when you extract msgs
…On Wed, May 16, 2018 at 7:15 PM Jeffery ZHAO ***@***.***> wrote:
1. You need level 0 for LSB.
2. The algorithm was designed in the way that you can always extract
messages, but with incorrect key, the message is wrong. This is intended
such that people don’t know whether it’s something inside the image if they
don’t know the password. The crash is due to the same reason (You are
decrypting something meaningless) and again it’s intended
On Wed, May 16, 2018 at 6:54 PM ChenYou ***@***.***> wrote:
> @zeruniverse <https://github.com/zeruniverse> thanks for your quick
> reply!
> I've tested on stego.js.org, using a png with transparent background a
> simple message "1", using Level 1 to write image
> [image: star_png1580]
> <https://user-images.githubusercontent.com/1531217/40152231-fc316040-59b6-11e8-82f1-3ac898d72d4f.png>
> Write can be performed successfully, but the picture's background has
> been turned into *all black*. And this black-background png image's
> message *can be read successfully*.
>
> But when I read message from a transparent background png image *with no
> message contained*, it will caused my Chrome *stuck and crash*.
>
> BTW, when I try to read some message from a picture (*with background*)
> which has no message contained, it will show some messy characters. I don't
> know the algorithm behind stego, but I wonder if there any possible
> enhancement to make this behavior better?
>
> Thanks!
>
> —
> You are receiving this because you were mentioned.
>
>
> Reply to this email directly, view it on GitHub
> <#7 (comment)>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AEbvNIowPNNs45EuKEdZVjnZN5o8rGeHks5tzNhQgaJpZM4UBSQz>
> .
>
Thanks.. So the crash is intended ? I get it..
I indeed use level 0 for LSB.. the above comment 'level 1' is a typo. sorry.
Still the transparent backgound is turned into black when write message to a transparent png
The crash is due to message not correct. and it’s intended that the program
has no way to check if the message is correct.
Don’t use transparent background. The current design does not consider the
transparent case
…On Wed, May 16, 2018 at 7:58 PM ChenYou ***@***.***> wrote:
Thanks.. So the crash is intended ? I get it..
I indeed use level 0 for LSB.. the above comment 'level 1' is a typo.
sorry.
Still the transparent backgound is turned into black when write message to
a transparent png
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<#7 (comment)>,
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Again if you do want to know if an image has valid message. Write some
verification bits at very beginning and you can check them easily later
…On Wed, May 16, 2018 at 8:22 PM Jeffery ZHAO ***@***.***> wrote:
The crash is due to message not correct. and it’s intended that the
program has no way to check if the message is correct.
Don’t use transparent background. The current design does not consider the
transparent case
On Wed, May 16, 2018 at 7:58 PM ChenYou ***@***.***> wrote:
> Thanks.. So the crash is intended ? I get it..
> I indeed use level 0 for LSB.. the above comment 'level 1' is a typo.
> sorry.
> Still the transparent backgound is turned into black when write message
> to a transparent png
>
> —
> You are receiving this because you were mentioned.
>
>
> Reply to this email directly, view it on GitHub
> <#7 (comment)>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AEbvNNNWeQLeYYt1OF7wsO3vLUjyomcvks5tzOdUgaJpZM4UBSQz>
> .
>
Ok, thanks for the help!