Re: [PATCH v6] lib/hash: add siphash

[Stephen Hemminger <stephen@networkplumber.org>]

On Wed, 16 Oct 2024 16:48:12 +0100
"Medvedkin, Vladimir" <vladimir.medvedkin@intel.com> wrote:

> Hi Stephen,
> 
> Thanks for introducing this hash function.
> 
> I have just a few nits:
> 
> On 01/08/2024 16:31, Stephen Hemminger wrote:
> > The existing hash functions in DPDK are not cryptographically
> > secure and can be subject to carefully crafted packets causing
> > DoS attack.  
> Currently in DPDK we have 3 hash functions, 2 of them can be used with 
> our cuckoo hash table implementation:
> 
> 1. CRC - Very weak, do not use with hash table if you don't fully 
> control all keys to install into a hash table.
> 
> 2. Toeplitz - keyed hash function, not used with hash tables, fastest if 
> you have GFNI, level of diffusion fully depends on the hash key, weak 
> against differential crypto analysis. Technically may be used with hash 
> tables in number of usecases.
> 
> 3. Jenkins hash (lookup3) - and here I can not say that it is not secure 
> and it is subject to collisions. I'm not aware on any successful attacks 
> on it, it has a great diffusion (see https://doi.org/10.1002/spe.2179). 
> It is also keyed with the same size of the key as rte_hsiphash().
> 
> So I won't agree with this sentence.

I am not a crypto or hash expert. This text is based on the statements
by the original author of siphash who does have such expertise.
See the wikipedia page:  https://en.wikipedia.org/wiki/SipHash
and the original paper: 
https://web.archive.org/web/20170327151630/https://131002.net/siphash/siphash.pdf

The problem is that Jenkins and Toeplitz
"were designed to have a close-to-uniform distribution, not to
meet any particular cryptographic goals"