From: Luke Dashjr <luke@dashjr.org>
To: bitcoin-dev@lists.linuxfoundation.org, Matthew Roberts <matthew@roberts.pm>
Date: Thu, 4 Aug 2016 03:27:34 +0000
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Subject: Re: [bitcoin-dev] BIP clearing house addresses
Precedence: list

On Wednesday, August 03, 2016 6:16:20 PM Matthew Roberts via bitcoin-dev 
wrote:
> In light of the recent hack: what does everyone think of the idea of
> creating a new address type that has a reversal key and settlement layer
> that can be used to revoke transactions?

This isn't something that makes sense at the address, since it represents the 
recipient and not the sender. Transactions are not sent from addresses ever.

> You could specify so that transactions "sent" from these addresses must
> receive N confirmations before they can't be revoked, after which the
> transaction is "settled" and the coins become redeemable from their
> destination output. A settlement phase would also mean that a transaction's
> progress was publicly visible so transparent fraud prevention and auditing
> would become possible by anyone.

This is already possible. Just nLockTime your withdrawls for some future 
block. Don't sign any transaction that isn't nLockTime'd at least N blocks 
beyond the present tip.

Luke