Implementing BIP69 for May2022

A previous post by @markblundeberg here details a short list of possible differences wallets can form valid transactions. These differences allow for fingerprinting, a technique which can reveal which wallet software was used to create which transactions. This is a privacy issue which should be mitigated as much as possible.

BIP69 is a low hanging fruit on this list. The BIP69 full spec can be found here. BIP69 eliminates the ability to fingerprint a wallet via intput/output ordering for commonly used transaction formats by deterministically sorting the inputs and outputs lexicographically. BIP69 is not a part of consensus and is not intended to be.

As a step towards increasing the privacy of transactions, I encourage wallet developers to implement BIP69 and have it enabled by default (when applicable) in time for the may2022 upgrade. If you are not a developer please encourage the developers of the wallet you use to make this suggested change.

Below is a list of wallets who either already support or plan to support for May. Please make a comment in this thread if you have information about additional wallets that can be added to this list.

Wallets that use BIP69

  • Electron Cash

Wallets that plan to implement it for May2022

  • BCHN
  • BU

Are there any downsides to BIP69, besides the fact that it creates some work for wallet developers? Any downsides for user privacy that we could forsee?

It is a very small change and the work created is minimal.
Overall, this BIP increases privacy for those who imeplement it. The only downside might be that if not every wallet implements it then it will be easier to identify which transactions came from a non BIP69 wallet. The solution for the wallet developer is to implement BIP69.