[bitcoin-dev] Fwd: P2WPKH Scripts, P2PKH Addresses, and Uncompressed Public Keys

[Gregory Maxwell <greg@xiph.org>]

On Mon, Aug 28, 2017 at 3:29 PM, Alex Nagy via bitcoin-dev
<bitcoin-dev@lists.linuxfoundation.org> wrote:
> If Alice gives Bob 1MsHWS1BnwMc3tLE8G35UXsS58fKipzB7a, is there any way Bob
> can safely issue Native P2WPKH outputs to Alice?

Absolutely not. You can only pay people to a script pubkey that they
have specified.

Trying to construct some alternative one that they didn't specify but
in theory could spend would be like "paying someone" by putting a
cheque in a locked safe labeled "danger radioactive" that you quietly
bury in their back yard.  Or taking the payment envelope they gave you
stuffing it with cash after changing the destination name to pig latin
and hiding it in the nook of a tree they once climbed as a child.

There have been technical reasons why some wallets would sometimes
display some outputs they didn't generate but could spend, but these
cases are flaws-- they're not generic for all cases they could in
theory spend, and mostly exist because durability to backup recovery
makes it impossible for it to tell what it did or didn't issue.

So regardless of your query about uncompressed keys, you cannot do
what you described: Wallets will not see the payment and may have no
mechanism to recover it even if you tell the recipient what you've
done. And yes, the use of an uncompressed yet could later render it
unspendable.