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A comment on Designing a New PRNG. Parent comment

Re:Designing a New PRNG by zokier on Monday December 20, 2021 @04:17PM (#29630398)
Seems that vigna (author of the xoshiro family of rngs) mostly agrees with you

> Personally, I don't believe in the "middle ground" of "difficult-to-predict-but-not-crypto": usually it just means it is so easy to break that nobody

https://github.com/rust-random/rand/issues/905#issuecomment-...

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Re:Designing a New PRNG by omoikane on Monday December 20, 2021 @05:37PM (#29631349)
I wish that issue would also link to the rebuttal: https://www.pcg-random.org/posts/on-vignas-pcg-critique.html
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Re:Designing a New PRNG by ttybird2 on Monday December 20, 2021 @09:46PM (#29633216)
https://www.pcg-random.org/

PCG's statistical quality is "excellent" but chacha20's just "good"?

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Re:Designing a New PRNG by loeg on Tuesday December 21, 2021 @01:16AM (#29634547)
It is a bit odd. I think the PCG authors are talking about reduced-round variants below 8[1] re: statistical quality. I agree it doesn't belong in a row labeled "ChaCha20." It seems obvious that chacha below 4 rounds is total garbage[2] but I don't know much about 4-7 rounds. The Too Much Crypto guy likes 8 rounds for cryptographic purposes.

[1]: https://www.pcg-random.org/other-rngs.html#id7

[2]: https://cr.yp.to/snuffle/diffusion.html

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Re:Designing a New PRNG by tptacek on Monday December 20, 2021 @09:29PM (#29633126)
Do you find that rebuttal persuasive? For someone who doesn't care at all about anyone's "tone", and just wants to know what the hell is going on with these constructions, I didn't find much there.
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Re:Designing a New PRNG by omoikane on Monday December 20, 2021 @11:28PM (#29633879)
My reading of both:

- Vigna claims small differences in internal states don't have avalanche effects, and the rebuttal says those small differences in internal states don't occur normally, not with the proper seeding steps.

- Vigna claims to be able to predict one particular variant of PCG, and the rebuttal said that that was one of the weaker variants that specifically has "insecure" in the name.

It's persuasive to me in suggesting that Vigna's claims are perhaps not that clear cut.

I am not an expert in PRNG and I wouldn't say this makes PCG win over Xorshiro or not, I just think it's unfortunate that the issue above linked only one side of the argument, especially since I find the other side more pleasant to read.

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