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posted by hubie on Wednesday September 28, @03:23AM   Printer-friendly
from the very-1337-hash dept.

Arthur T Knackerbracket has processed the following story:

Generating checksums—cryptographic hashes such as MD5 or SHA-256 functions for files is hardly anything new and one of the most efficient means to ascertain the integrity of a file, or to check if two files are identical.

However, generating a file containing its own checksum as part of its content is a task quite daunting, if not seemingly impossible due to a paradox involved in the process.

That has not stopped a researcher from creating a PNG image that contains the file's MD5 checksum, visible within the matrix of pixels that make up the image.

[...] BleepingComputer confirmed the checksum of the image in question is 1337e2ef42b9bee8de06a4d223a51337, which are the characters displayed vertically within the image itself.

[...] A checksum is a smaller-sized chunk of data, or even a digit, derived from another set of digital data as a means to detect errors or data corruption that may have occurred. The idea is that any minor change occurring to the original file or piece of data will alter its checksum indicating that the integrity of the data is now void.

[...] You need the checksum or hash of a file first to include this information within the content of the file itself. But doing so by editing or altering the file will effectively change the file's checksum, therefore making this practice seem impossible.

[...] What Buchanan essentially created is colloquially called a "Hashquine," a term coined in 2017 by hardware and software enthusiast, foone to refer to files that show their own hash.

The same year, Google security engineers, known as spq and Ange Albertini successfully demonstrated the concept by respectively generating GIF and Postscript files that displayed their own hash as part of the file's contents:

[...] What Buchanan has demonstrated today, however, essentially makes the MD5 hashquine technique possible for PNG files.

[...] "Ever since, I wanted to make a PNG hashquine. I thought about it for a while, but couldn't figure it out - the same tricks used for the GIF file format can't be directly applied to PNG."

[...] Buchanan has shared a detailed technical breakdown in a Twitter thread on how he was able to land on his hashquine, and it has to do with leveraging hash collisions:

[...]  It seems it'll be a while until, much like Rogdham, Buchanan is also able to release his code for PNG-MD5 hashquines.

The researcher tells BleepingComputer he's further refining the code which at the time is "a bit of a rube goldberg machine" and potentially working on a paper.

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  • (Score: 2) by canopic jug on Wednesday September 28, @04:00AM (1 child)

    by canopic jug (3949) Subscriber Badge on Wednesday September 28, @04:00AM (#1273973) Journal

    MD5 collisions for images have been feasible with normal hardware for about a decade now. I looked around a bit but could not find an actual reference for this new claim. This would be interesting to read about if it were published by a reliable source. Images containing their own MD5 hashes have been around for a few years, but this might be some advancement or breakthrough in the process. The above summary points to Bleeping Computer which is fairly dodgy to begin with and it in turn points to some heresay aka "tweets".

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  • (Score: 4, Insightful) by c0lo on Wednesday September 28, @04:07AM

    by c0lo (156) on Wednesday September 28, @04:07AM (#1273978) Journal

    Now do it with SHA2/512 (grin)

  • (Score: 2) by number11 on Wednesday September 28, @05:26AM (2 children)

    by number11 (1170) on Wednesday September 28, @05:26AM (#1273986)

    Checksums are, I think, not the same as hashes. A check digit or a parity bit is a (very simple) form of checksum. At least, back in the old days, a checksum was derived by adding up all the bytes, and the checksum was the remainder mod whatever. CP/M used this to detect files that were changed but had not been properly closed (which would write any final changes, and a new checksum, to disk) and thus probably corrupt. And it worked. 255/256 of the time. (But there was that 1/256 chance that the checksum would be the same even though the file had been changed, and then you were hosed.)

    • (Score: 2) by HiThere on Wednesday September 28, @01:39PM

      by HiThere (866) on Wednesday September 28, @01:39PM (#1274029) Journal

      Well, with many definitions they are different ways of describing the same thing. If you had a table with 125 entries you could use your CP/M checksum as the index. (Which is why some implementations of hash tables have the index pointing to a list of matches that have been entered.)

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    • (Score: 0) by Anonymous Coward on Wednesday September 28, @05:33PM

      by Anonymous Coward on Wednesday September 28, @05:33PM (#1274064)

      Checksum are meant to catch accidental changes (e.g., errors/corruption of data). Hashes are made to stop intentional ones (malicious intent).

  • (Score: 5, Funny) by mhajicek on Wednesday September 28, @08:19AM

    by mhajicek (51) on Wednesday September 28, @08:19AM (#1273997)

    Bonus points for beginning and ending the hash with "1337".

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