The case of the 9 bit AES key
48 points by ledoge 3 hours ago | 16 comments

tptacek 24 minutes ago
"MuPDF versions before 1.28.5 use an implementation of the drand48 family" yeah, ok, so they're basically not doing real encryption. The number of bits in the key space isn't the real story; the keys simply aren't cryptographically random.
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ubutler 35 minutes ago
Rule #1 of rolling your own RNG: don’t.

Rule #2? Please don’t.

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j16sdiz 23 minutes ago
That's why we use the system RNG !
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flanz_10 7 minutes ago
btw, the idea that the system rng isnt good enough, or "runs out" or whatever, is no longer true on pretty much every modern, widely used os.

btw... im sure there's some legacy rng in windows or some shit that isnt good. read the docs but if it's the blessed system rng, you're probably fine!

although... i suppose if this is news to you (the person reading this), then you probably shouldn't be implementing whatever you are that really requires prng. ask a friend for help. im not trying to be a jerk, i just want to make sure you dont hurt yourself!

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JonChesterfield 49 minutes ago
Wonderful.
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paulpauper 3 hours ago
it's like the weak hardware wallet entropy bug
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jeffbee 2 hours ago
You'd have to be completely off your rocker to use a PDF tool written in C anyway.
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advisedwang 53 minutes ago
very VERY few people judge tools like this by the language used to develop them.
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jeffbee 44 minutes ago
How many people judge their tools based on the AES key entropy?
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OptionX 29 minutes ago
A lot actually.

You're confusing just assuming by default its enough for purpose rather than not caring at all.

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j16sdiz 19 minutes ago
just down vote it.

You can downvote anything not interesting.

If he have list some alternative or give example, it might be interesting.

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cowlevel 2 hours ago
What are the alternatives?
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crote 17 minutes ago
PDF.js, for example. It's what Firefox uses, and most websites with integrated on-page PDF viewing functionality.
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lirolero 2 hours ago
Genuine question, since I'm not very knowledgeable about this: why is using C for a PDF tool such a bad idea?
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tptacek 22 minutes ago
I think the claim is hyperbolic, since most people memory-unsafe PDF implementations, but PDF is a monster format, a metaformat that brings in virtually every conceivable display format, and their renderer implementations with them, often poorly-maintained, never-touched reference implementations from the before times. PDF is pretty scary.
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recursive 23 minutes ago
buffer overflow vulnerability in code dealing with user generated data and a complex file format.
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