[Cryptography] an associative hash function

[David Leon Gil]

On Wed, May 27, 2015 at 10:47 AM, Jelle van den Hooff
<jelle at vandenhooff.name> wrote:
> An associative hash function is a hash function
> that allows you to efficiently calculate hash(concat(a, b)) from hash(a) and
> hash(b).

I quite like the construction, so I thought I'd note that this may
have some applications in anonymous routing as well.

> There is a small catch, as the associative hash function described has an
> output that grows in size as O(log n), instead of the O(1) delivered by SHA
> et al. That is, for now, the price to pay for associativity.

Perhaps a construction from lattice-based CRHFs might achieve O(1)?