Mailing List Archive: add-photo continued ...

add-photo continued ...

gnupg-users at gnupg

Sep 4, 2019, 11:45 AM

Post #1 of 7 (999 views)

Hi all,

some of you may remember the add-photo thread we had a while ago
and I wondered why the max image size for a UAT packet is 16 MB.

Recently I saw a Twitter post explaining that a .jpeg image header
can contain 16 MB of data. I do not have the link currently handy,
sorry!

So here is a little keyserver test showing data in a .jpeg header
of a UAT packet.

It is a zipped folder containing 10 little 'messages' created with
openssl.

As keyserver I used the Ubuntu keyserver because it is then easier
for users to extract the data. Simple right-click on the image and
then once saved as index.jpg do an 'unzip index.jpg' to obtain the
folder with the text files.

<https://keyserver.ubuntu.com/pks/lookup?search=0x9101026E485CA9DE&fingerprint=on&op=index>

Regards
Stefan

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Re: add-photo continued ... [ In reply to ]

gnupg-users at gnupg

Sep 4, 2019, 4:16 PM

Post #2 of 7 (999 views)

Stefan Claas via Gnupg-users wrote:

> Recently I saw a Twitter post explaining that a .jpeg image header
> can contain 16 MB of data. I do not have the link currently handy,
> sorry!

I think I talked nonsense here about the 16 MB header size! Hopefully
I can find the authors technique again, because he posted the source
code too ...

Regards
Stefan

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Re: add-photo continued ... [ In reply to ]

gnupg-users at gnupg

Sep 4, 2019, 4:43 PM

Post #3 of 7 (999 views)

Stefan Claas via Gnupg-users wrote:

> Hi all,
>
> some of you may remember the add-photo thread we had a while ago
> and I wondered why the max image size for a UAT packet is 16 MB.
>
> Recently I saw a Twitter post explaining that a .jpeg image header
> can contain 16 MB of data.

That's just decadence. :-)
Just because it can, doesn't mean it should.
16MB is plenty. Use tinypng.com.

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Re: add-photo continued ... [ In reply to ]

gnupg-users at gnupg

Sep 5, 2019, 12:44 AM

Post #4 of 7 (999 views)

On 2019-09-05 01:16, Stefan Claas via Gnupg-users wrote:
> Stefan Claas via Gnupg-users wrote:
>
>> Recently I saw a Twitter post explaining that a .jpeg image header
>> can contain 16 MB of data. I do not have the link currently handy,
>> sorry!
>
> I think I talked nonsense here about the 16 MB header size! Hopefully
> I can find the authors technique again, because he posted the source
> code too ...

No, seems not to be nonsense, as understood.

https://dev.exiv2.org/projects/exiv2/wiki/The_Metadata_in_JPEG_files

2.4 ICC

The maximum size of an ICC profile is limited to 256 * (63535 - 16) =
16,261,888 bytes. This is quite a large profile!

I wonder what kind of data would require such a max size.

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Re: add-photo continued ... [ In reply to ]

gnupg-users at gnupg

Sep 5, 2019, 8:27 AM

Post #5 of 7 (995 views)

raf via Gnupg-users wrote:

> Stefan Claas via Gnupg-users wrote:
>
> > Hi all,
> >
> > some of you may remember the add-photo thread we had a while ago
> > and I wondered why the max image size for a UAT packet is 16 MB.
> >
> > Recently I saw a Twitter post explaining that a .jpeg image header
> > can contain 16 MB of data.
>
> That's just decadence. :-)
> Just because it can, doesn't mean it should.
> 16MB is plenty. Use tinypng.com.

Well, at least people can use this teqnique to fire-up important
documents, which should be preserverd for the next generations,
since SKS is censor resistant and the Ubuntu keyserver allows
easy retrival of documents ...

BTW. I just found also the authors link on twitter.

https://twitter.com/David3141593/status/1057042085029822464

Regards
Stefan

--
box: 4a64758de9e8ceded2c481ee526440687fe2f3a828e3a813f87753ad30847b56
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Re: add-photo continued ... [ In reply to ]

gnupg-users at gnupg

Dec 29, 2019, 4:23 PM

Post #6 of 7 (971 views)

Stefan Claas via Gnupg-users wrote:

> raf via Gnupg-users wrote:
>
> > Stefan Claas via Gnupg-users wrote:
> >
> > > Hi all,
> > >
> > > some of you may remember the add-photo thread we had a while ago
> > > and I wondered why the max image size for a UAT packet is 16 MB.
> > >
> > > Recently I saw a Twitter post explaining that a .jpeg image header
> > > can contain 16 MB of data.
> >
> > That's just decadence. :-)
> > Just because it can, doesn't mean it should.
> > 16MB is plenty. Use tinypng.com.
>
> Well, at least people can use this teqnique to fire-up important
> documents, which should be preserverd for the next generations,
> since SKS is censor resistant and the Ubuntu keyserver allows
> easy retrival of documents ...
>
> BTW. I just found also the authors link on twitter.
>
> https://twitter.com/David3141593/status/1057042085029822464

In case people here haven't seen yet.

<https://keyserver.ubuntu.com/pks/lookup?search=0x7b96d396e6471601754be4db53b620d01ce0c630&fingerprint=on&op=vindex>

Regards
Stefan

--
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Re: add-photo continued ... [ In reply to ]

gnupg-users at gnupg

Jan 4, 2020, 5:08 AM

Post #7 of 7 (966 views)

Stefan Claas via Gnupg-users wrote:

> Stefan Claas via Gnupg-users wrote:
>
> > raf via Gnupg-users wrote:
> >
> > > Stefan Claas via Gnupg-users wrote:
> > >
> > > > Hi all,
> > > >
> > > > some of you may remember the add-photo thread we had a while ago
> > > > and I wondered why the max image size for a UAT packet is 16 MB.
> > > >
> > > > Recently I saw a Twitter post explaining that a .jpeg image header
> > > > can contain 16 MB of data.
> > >
> > > That's just decadence. :-)
> > > Just because it can, doesn't mean it should.
> > > 16MB is plenty. Use tinypng.com.
> >
> > Well, at least people can use this teqnique to fire-up important
> > documents, which should be preserverd for the next generations,
> > since SKS is censor resistant and the Ubuntu keyserver allows
> > easy retrival of documents ...
> >
> > BTW. I just found also the authors link on twitter.
> >
> > https://twitter.com/David3141593/status/1057042085029822464
>
> In case people here haven't seen yet.
>
> <https://keyserver.ubuntu.com/pks/lookup?search=0x7b96d396e6471601754be4db53b620d01ce0c630&fingerprint=on&op=vindex>

https://github.com/hockeypuck/hockeypuck/issues/68

Regards
Stefan

--
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