BUIP082: opt-in malleability fix
Proposer: Gal Buki (@torusJKL)
Submitted on: 2017-12-25
Status: passed 

Background

Malleability is not an issue when working only with confirmed tx. But if
an application wants to reference an unconfirmed tx based on its tx id
it could fail if said id is changed (malleate).

Motivation

Allow applications to use unconfirmed tx based on a non-malleable id.
This could open up Bitcoin Cash to new technology we do not know of
today.

Goal

The solution will make tx non-malleable by the 1st party. It should be
opt-in and mustn’t require existing inputs to be moved first (e.g. with
SegWit where the tx has to originate from a SegWit address).

Task

1. The Bitcoin Unlimited lead developer shall engage in the discussion
   with other consensus implementations and propose a solution. The
   solution can be already proposed by others or be a new one.
2. Writing of a specification and a pull request to the BitcoinCash
   repo such that other develops can implement the solution in their
   software.
3. Development of the malleability fix for BUCash.

Timetable

The malleability fix should be developed and to be implemented for
BUCash with the aim of being ready for inclusion in the scheduled
November 2018 protocol upgrade.

Caveats

The lead developer will have discretion and flexibility to modify
details specified in this BUIP, while keeping within the spirit of the
BUIP with the goal of advancing an opt-in malleability fix for Bitcoin
Cash.

References

- Malleability fix
proposal

- Malleability Fix
SIGHASH_ANYOUTPUT

- Start differenciating txid and
txhash