> Betterhash has security improvements to stratum to prevent hijacking.
There's actually very little done w.r.t. "improving security" in Betterhash.
The primary [motivation](https://github.com/TheBlueMatt/bips/blob/betterhash/bip-XXXX.mediawiki#motivation) behind Betterhash is better decentralization. And of course, any new protocol has to think about potential attacks to the new scheme, which Matt obviously looked into (ref "Why are some messages signed and others not?" in the [linked doc](https://github.com/TheBlueMatt/bips/blob/betterhash/bip-XXXX.mediawiki#discussion)).
Betterhash is, in my opinion, great work. However, it is very much focused on the Bitcoin mining landscape (e.g. ASICs), and it is far more effort to implement than a simple mode change to the existing stratum protocol.
No, it is not a change to Bitcoin, the hashing algorithm, or its consensus rules in any way.
EDIT: I only now look at the title. "New hashing protocols" doesn't mean new PoW hash *function*. It's just a better protocol for communication between hashers, pools, and nodes to select the contents of blocks.
Edit: just to clarify, this isnotabout a new hashing algorithm or some consensus change. It's about a new protocol regulating the relationship between the pool operators and the individual miners, contributing to a pool. With Betterhash, individual miner get more control what to mine and how to construct blocks (currently, the pool operators have the power to decide how to use the hashrate exactly).
This is an article by u/StopAndDecrypt on why the BetterHash protocol (developed by Matt Corallo) is important, and which currently possible attacks/collusions (from miner's side) it prevents, if adopted in the future. Very educational write up.