Re: [PATCH v5 2/3] KEYS: Replace assoc_array with rhashtable

[Eric Biggers]

On Fri, Nov 06, 2026 at 09:21:32AM +0100, Hannes Reinecke wrote:
> While I am pretty much in favour with this approach, is there a specific
> reason why siphash has been chosen?

SipHash is the preferred choice for secure hash tables.  It is secure,
performs well on short inputs, and doesn't require special instructions.
See Documentation/security/siphash.rst

> Would there be a chance to make this configurable?
> I do see slight complications when running in secure environments
> (ie FIPS-certified environments) where most of the hash functions
> might not be available ...

SipHash support is available even when the kernel is booted with fips=1,
so there's no issue there.  It's already widely used in the kernel for
hash tables, and that hasn't blocked FIPS certifications either.

Side note: fips=1 actually has little do with security, and in some
cases it actually decreases security.  See for example
https://lore.kernel.org/linux-crypto/20261026183332.11402-1-ebiggers@xxxxxxxxxx/
where I'm fixing a vulnerability caused by fips=1.

- Eric