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Filtration Residue
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horst



Joined: 06 Mar 2009
Posts: 24
Location: Germany

Post Filtration Residue Reply with quote
I've extracted some information from the image but I have no clue what the solution is. Any hints?
Thu Oct 01, 2009 10:37 am View user's profile Send private message
michuber



Joined: 26 Oct 2008
Posts: 57

Post Reply with quote
You should consider the first sentence of the last paragraph.
Fri Oct 02, 2009 2:44 pm View user's profile Send private message
jonik555



Joined: 31 Aug 2009
Posts: 43
Location: Prague

Post Reply with quote
I'm really stuck here, I have extracted informations too, but i cant find the answer, do You mean last paragraph of informations in picture? (is that sentence this? Xxx xxxxxx xxx xxxxxx xxxxx xx xxxxx xxxxxx xxxxxxxxxx xx xxxxx xx x xxxxxxxx-xx-xxxxxxxx xxxxx.) or last paragraph in whole information(not only part inside picture). Please help me little bit.

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There are 10 types of people, those who understand ternary, those who think that this joke is about binary and the others.
Thu Mar 11, 2010 5:54 pm View user's profile Send private message
michuber



Joined: 26 Oct 2008
Posts: 57

Post Reply with quote
Did you compare the extracted text to the original?
Thu Mar 11, 2010 9:00 pm View user's profile Send private message
teebee



Joined: 10 Nov 2008
Posts: 89
Location: Germany

Post Reply with quote
Yes, the crossed out sentence is the one pointed out by michuber. Moreover, you should read the excerpt carefully.
Thu Mar 11, 2010 9:01 pm View user's profile Send private message
jonik555



Joined: 31 Aug 2009
Posts: 43
Location: Prague

Post Reply with quote
Thank you, but I still dont understand this sentence. yes i compared it and found something added to table, but dont know what to do with it. what is the form of answer? and is the filter type the one used in IHDR header?

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There are 10 types of people, those who understand ternary, those who think that this joke is about binary and the others.
Fri Mar 12, 2010 6:18 am View user's profile Send private message
laz0r



Joined: 04 Feb 2010
Posts: 290
Location: Within the depths of Unix

Post Reply with quote
Any help on how to extract the information in the first place?

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There is no spoon.
Fri Mar 12, 2010 5:00 pm View user's profile Send private message
jonik555



Joined: 31 Aug 2009
Posts: 43
Location: Prague

Post Reply with quote
Yes. I have got it! Many thanks for hints.

_________________
There are 10 types of people, those who understand ternary, those who think that this joke is about binary and the others.
Wed Mar 17, 2010 5:37 pm View user's profile Send private message
Adriano



Joined: 17 Oct 2010
Posts: 6

Post Reply with quote
That was a tricky one - and it brought me some deeper understanding of the PNG spec.. Wink
Thanks for the hints!
Sat Oct 23, 2010 8:17 pm View user's profile Send private message
HugStuart



Joined: 25 Oct 2008
Posts: 13

Post Reply with quote
Thank you all for this discussion. It helped a lot to solve this challenge. Once you are on the right track it's not that hard. I just wonder if there are some similiarities to "Lucy in the Sky with Briolettes" Rolling Eyes
Tue Oct 26, 2010 1:41 pm View user's profile Send private message ICQ Number
michuber



Joined: 26 Oct 2008
Posts: 57

Post Reply with quote
HugStuart wrote:
I just wonder if there are some similiarities to "Lucy in the Sky with Briolettes"

This is a good hint for those who don't know the song.
Tue Oct 26, 2010 2:50 pm View user's profile Send private message
MyNameIsAlreadyTaken



Joined: 17 Oct 2010
Posts: 31
Location: Germany

Post Reply with quote
Alright, I'm pretty sure I'm on the right track [already decoded the first message], but for the next step i need to decompress the PNG-File.

From what I've understood in the PNG-specifications, I need to concat the content of all IDAT-chunks and it is decompressed using the LZ77-algorithm. The first step wasn't a big deal, but how can i decompress it now? I've tried to simply decompress it with gzip -d file.gz, but it didn't work.


Could maybe someone hint me on how to decompress the file?


Edit: Alright, my approach to try to convert the PNG-Data into a gzip file failed, since I don't know the crc32 of the original data. Fortunately, I got a hint via pm, that one of the tools I used had a nice option that wasn't documented in the manpages.
Fri Oct 29, 2010 12:16 pm View user's profile Send private message
polarlemniscate



Joined: 03 Mar 2010
Posts: 6

Post Reply with quote
Any hints as to which tool?
Quote:
n
PostPosted: Fri Oct 29, 2010 12:16 pm Post subject:
Alright, I'm pretty sure I'm on the right track [already decoded the first message], but for the next step i need to decompress the PNG-File.

From what I've understood in the PNG-specifications, I need to concat the content of all IDAT-chunks and it is decompressed using the LZ77-algorithm. The first step wasn't a big deal, but how can i decompress it now? I've tried to simply decompress it with gzip -d file.gz, but it didn't work.


Could maybe someone hint me on how to decompress the file?


Edit: Alright, my approach to try to convert the PNG-Data into a gzip file failed, since I don't know the crc32 of the original data. Fortunately, I got a hint via pm, that one of the tools I used had a nice option that wasn't documented in the manpages.

Fri Oct 29, 2010 8:28 pm View user's profile Send private message
MyNameIsAlreadyTaken



Joined: 17 Oct 2010
Posts: 31
Location: Germany

Post Reply with quote
It was [tool removed, sorry guys], my manpages most seemingly weren't up-to-date.


I hope this isn't too much of a spoiler, it's just the tool - people will still need to think of what they got to do with the data.
Fri Oct 29, 2010 9:09 pm View user's profile Send private message
laz0r



Joined: 04 Feb 2010
Posts: 290
Location: Within the depths of Unix

Post Reply with quote
Ok, I've successfully decoded the message within and found a few differences within the table. However, do I need to consider all the random spacing and dots?

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There is no spoon.
Wed Dec 08, 2010 1:23 pm View user's profile Send private message
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