Sip RNG

[dhardy]

I have implemented a psuedo-random number generator based on SipHash, and hope I might be able to get some feedback on the design?

This PRNG construction appears to be statistically high-quality, though only with moderate speed, and I don't know about cryptographic strength.

The motivation to doing this is to provide a "universal PRNG seeder", meaning:

• any input can be deterministically transformed into a key of any required size
• the output key has a high chance of avoiding low hamming-weight values even for naive input
• for similar input values, there is a high chance that the output keys are very different

This is not intended for use in cryptography, but only for deterministic PRNGs used in simulations.

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The choice of how many rounds to use, and where, is arbitrary, but designed to be similar to the standard 2-4 selection used by SipHash.

The additional tweaks to state between these rounds are entirely arbitrary choices other than being some extra tweak.

A quick guide to the source code:

• 39, 57, 69: hasher state
• 51, 69: RNG state
• 320: SipHash::write function
• 216: SipHash for short input
• 361: SipHash::finish function for standard output
• 242: conversion from SipHash to SipRng
• 146: SipRng::next_u64 function
• 410: c_rounds / d_rounds functions
• 440, 462: test vectors

[veorq]

This is not the right place for such review work.