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Not A Number
Personal blog · notanumber.netprogrammingmath
Not A Number is a personal blog at notanumber.net about programming and math. Since 2010, 7 different Hacker News readers have linked it 8 times, most often “Underhanded C: The Leaky Redaction”. The last post was in 2020, but the archive is still widely read.
Too few sampled comments (4) to say how often HN recommends it.?
Why HN links it
HN readers link this blog for its entry in the 2008 Underhanded C Contest, which shows a leaky redaction trick in which hidden data survives in PPM image format.
Summarised by Claude from a sample of 4 HN comments that link here. Each comment is marked recommending, critical or neutral (citing without judging); how this works.
Programming, Theory, and Math
Most-linked posts?
- Underhanded C: The Leaky Redaction4 people · 5 mentions · first linked 2010-12-23
- Not a Number – Cuckoo Byte Stuffing Algorithm2 people · 2 mentions · first linked 2014-05-16
What Hacker News says?
The 2008 Underhanded C Contest [1] had an exercise in "leaky" redaction. The winner, [2], used a very fun approach. [1] http://www.underhanded-c.org/_page_id_17.html [2] http://notanumber.net/archives/54/underhanded-c-the-leaky-re...
Comment linking /archives/54/underhanded-c-the-leaky-redaction
on “How the US Pushed Sweden to Take Down the Pirate Bay”Submitted Underhanded C: The Leaky Redaction as a story · 63 points
HN discussionHere is the link if anyone's interested: http://notanumber.net/archives/54/underhanded-c-the-leaky-re...
Comment linking /archives/54/underhanded-c-the-leaky-redaction
on “A tool for recovering passwords from pixelized screenshots”Submitted Not a Number – Cuckoo Byte Stuffing Algorithm as a story · 2 points
HN discussionI remember that one: the two blacks were not slightly different, they were both exactly black but written in different ways. The image was in PPM format, which stores the color components of the pixels as ASCII text (so a white pixel is stored as "255 255 255" and a black one is "0 0 0"). To redact the image, the code replaced every digit of the numbers with '0', so white became "000 000 000" and black stayed as "0…
Comment linking /archives/54/underhanded-c-the-leaky-redaction
on “Sega mistakenly reveals sales numbers of popular games”Submitted Newtype in C, a touch of strong typing using compound literals as a story · 2 points
HN discussionReminds me of my favourite winner of the underhanded c contest, back in 2008 http://notanumber.net/archives/54/underhanded-c-the-leaky-re... Effectively this draws 'black boxes', but in a way that allows the developer to recover much information from the document if desired. The trick is in the ppm format, where a 0, 00, and 000 are all valid 'black' values. The redaction works by turning all 'digits' into zeros in…
Comment linking /archives/54/underhanded-c-the-leaky-redaction
on “How Not to Redact a Warhead”Submitted Cuckoo Byte Stuffing as a story · 1 points
HN discussion