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Just as you wouldn't want to use a general purpose PRNG for security applications so too you wouldn't want to use a secure PRNG for general purposes, particular

Just as you wouldn't want to use a general purpose PRNG for security applications so too you wouldn't want to use a secure PRNG for general purposes, particularly demanding applications such as Monte Carlo simulations. Your dismissal strikes me as both ignorant and rude.

JoachimS 11y ago
What are the random number data rates for those applications? One of the good features of ChaCha is that it is fast. A modern CPU can churn out Gbps of data. And in HW you can do it at low clock frequencies. This is the reason we use ChaCha as the CSPRNG in the Cryptech HSM.
daurnimator 11y ago
> Just as you wouldn't want to use a general purpose PRNG for security applications so too you wouldn't want to use a secure PRNG for general purposes, particularly demanding applications such as Monte Carlo simulations. Why not? It's perfectly valid to use a secure RNG for non-secure purposes. As I mentioned, I've used ChaCha20 for those sort of purposes too. And the random number generation barely shows up as a fraction of the runtime. i.e. improving 1% of the runtime by 99% isn't worth the overhead of having more than one random number generator.
- danieltillett 11y ago
  The reason why is crypto RNG are much slower than something less secure. It really depends on the application, but in the code I wrote today a significant fraction of my application’s time was spent in the RNG function. By replacing the RNG I managed to speed up my code by a bit over 2 fold. I am not doing crypto work so this is great.
  - daurnimator 11y ago
    ChaCha is fast. very fast. see just below: https://news.ycombinator.com/item?id=9890599 https://news.ycombinator.com/item?id=9890599 I'm not sure why they marked it as "fairly slow" in the table in the OP.
    - danieltillett 11y ago
      Fast and slow are all relative - ChaCha is relatively fast but PGC is faster.
- ars 11y ago
  > Why not? It's perfectly valid to use a secure RNG for non-secure purposes. It's much slower. Yes, in your application it was a fraction, but they are still much slower than non-secure RNG's.
- eterm 11y ago
  One of the benefits of a PRNG is reproducibility. If you are doing a monte carlo simulation, then you can get good results while still starting runs from predictable seeds. (e.g. [0,1,2,3,4,...]) This gives you both good quality random numbers during the simulation run yet lets others reproduce your results and expand with more results if required.
  - dchest 11y ago
    ChaCha20 is a cipher, of course, it creates reproducible sequences.

JoachimS 11y ago

What are the random number data rates for those applications? One of the good features of ChaCha is that it is fast. A modern CPU can churn out Gbps of data. And in HW you can do it at low clock frequencies. This is the reason we use ChaCha as the CSPRNG in the Cryptech HSM.

daurnimator 11y ago

> Just as you wouldn't want to use a general purpose PRNG for security applications so too you wouldn't want to use a secure PRNG for general purposes, particularly demanding applications such as Monte Carlo simulations. Why not? It's perfectly valid to use a secure RNG for non-secure purposes. As I mentioned, I've used ChaCha20 for those sort of purposes too. And the random number generation barely shows up as a fraction of the runtime. i.e. improving 1% of the runtime by 99% isn't worth the overhead of having more than one random number generator.

danieltillett 11y ago
The reason why is crypto RNG are much slower than something less secure. It really depends on the application, but in the code I wrote today a significant fraction of my application’s time was spent in the RNG function. By replacing the RNG I managed to speed up my code by a bit over 2 fold. I am not doing crypto work so this is great.
- daurnimator 11y ago
  ChaCha is fast. very fast. see just below: https://news.ycombinator.com/item?id=9890599 https://news.ycombinator.com/item?id=9890599 I'm not sure why they marked it as "fairly slow" in the table in the OP.
  - danieltillett 11y ago
    Fast and slow are all relative - ChaCha is relatively fast but PGC is faster.
ars 11y ago
> Why not? It's perfectly valid to use a secure RNG for non-secure purposes. It's much slower. Yes, in your application it was a fraction, but they are still much slower than non-secure RNG's.
eterm 11y ago
One of the benefits of a PRNG is reproducibility. If you are doing a monte carlo simulation, then you can get good results while still starting runs from predictable seeds. (e.g. [0,1,2,3,4,...]) This gives you both good quality random numbers during the simulation run yet lets others reproduce your results and expand with more results if required.
- dchest 11y ago
  ChaCha20 is a cipher, of course, it creates reproducible sequences.