On Sun, May 15, 2016 at 5:08 AM, Daniel Weigl via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org> wrote:

> 0x40000000 would be the next available to specify witness addresses.
> This is compatible with existing accounts and wallet layouts.

my main concern here is that
-) every Bip<this-bip>-compatible wallet in the future will have to implement all (then probably) legacy derivation and tx schemes.

I can see the advantage of a segwit only scheme, but we will need to support old derivations anyway for many decades if not indefinitely. People are using it to store value for the long term.

-) it does not fail in a deterministic way, if I import a seed or xPriv/xPub across different capable wallets.
It is more visible if one account has [no funds/does not show up] at all after an import than if something shows up but you need to make sure that the balance is what you might expect.

This is certainly a downside. It has to be weighed against the benefit of being able to upgrade existing wallets in place. Asking users to create a new wallet, and replace their recovery phrase backups is an even bigger problem in my estimation.

What do you think of doing both? A new BIP43 purpose number for segwit only wallets, but that also specifies 0x40000000/1 for the change/receive index so that the scheme is compatible with other schemes for upgrade existing wallets in place? There will certainly be wallet developers who decide to upgrade in place, but we can standardized both how to indicate segwit chains, independent of segwit only schemes or upgrade schemes, and still have the advantages of a new segwit only BIP43 purpose number.

Aaron Voisine

co-founder and CEO
breadwallet