Subject: Re: [bitcoin-dev] Proposed new policy for transactions that depend on other unconfirmed transactions

From: Taariq Lewis <[email-masked]>
Date: Wed, 7 Oct 2015 23:10:37 -0700

Our comment was posted to Github:
https://github.com/bitcoin/bitcoin/pull/6771#issuecomment-146429708

We, at Serica and DigitalTangible actively use unspent tx chains to allow
our customers to speed their bitcoin user-experience without the need for
them to wait on blockchain confirmations. These transactions are usually
sequential and must happen between our customers and our marketplace of
merchants and other customers. For example, a user agrees to place an order
to purchase bitcoin and then make a bitcoin payment, for a product or
services, with that bitcoin, should their desired price be met while they
are unable to actively monitor their transaction.

We currently do not have a need to chain more than 5 unspents given our
current use cases for onboarding new customers into the bitcoin ecosystem.
Given this PR, we agree with its principle, since the proposal aims to
limit to MAX_ANCESTORS = 25 and MAX_DESCENDANTS = 25, which we think is
reasonable. We have not **yet** seen a use case for more than 25 chains of
unconfirmed in our ecosystem.

However, we would like to publish our viewpoint that we wish to avoid a
slippery slope of restrictions in unspents to fall from from 25 to 2 or
even 0. The limits imposed should not prevent, at minimum, 5 step chains of
transactions that are needed to give a customer temporary control over
funds that they would otherwise not have access to unless they waited for a
confirmation before conducting another transaction. In these situations,
where an instant purchase must be made with customer control, that btc must
be sent to a customers address and then be quickly relayed to a merchant or
another party in a transaction to create a seamless experience. All of this
must happen within 0 confs because our customers will not wait for a whole
confirm and we do not wish to lose the opportunity to make Bitcoin more
available and useful to a broader audience with higher performance demands.

Zero confirmations, when done properly, help increase adoption of Bitcoin
and make it more competitive against other forms of payments. However, we
do think it's good to prevent abuse of the system with reasonable
constraints for the current ecosystem of applications and wallets.

Cheers,
Taariq Lewis & Serica/DigitalTangible team.

>
> ------------------------------
>
> Message: 2
> Date: Mon, 21 Sep 2015 11:02:20 -0400
> From: Alex Morcos <[email-masked]>
> To: Danny Thorpe <[email-masked]>
> Cc: Bitcoin Dev <[email-masked]>
> Subject: Re: [bitcoin-dev] Proposed new policy for transactions that
>         depend on other unconfirmed transactions
> Message-ID:
>         <CAPWm=
> [email-masked]>
> Content-Type: text/plain; charset="utf-8"
>
> Thanks for everyone's review.  These policy changes have been merged in to
> master in 6654 <https://github.com/bitcoin/bitcoin/pull/6654>, which just
> implements these limits and no mempool limiting yet.  The default ancestor
> package size limit is 900kb not 1MB.
>
> Yes I think these limits are generous, but they were designed to be as
> generous as was computationally feasible so they were unobjectionable
> (since the existing policy was no limits).  This does not preclude future
> changes to policy that would reduce these limits.
>
>
>

-- 
*Taariq Lewis*
p: +1-646-479-6098
e: [email-masked]