From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp1.osuosl.org (smtp1.osuosl.org [IPv6:2605:bc80:3010::138]) by lists.linuxfoundation.org (Postfix) with ESMTP id 6CD24C002F; Wed, 19 Jan 2022 07:32:54 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp1.osuosl.org (Postfix) with ESMTP id 3CF098199D; Wed, 19 Jan 2022 07:32:54 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org X-Spam-Flag: NO X-Spam-Score: -4.199 X-Spam-Level: X-Spam-Status: No, score=-4.199 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no Received: from smtp1.osuosl.org ([127.0.0.1]) by localhost (smtp1.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 78eMxSWm9oVj; Wed, 19 Jan 2022 07:32:52 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from outgoing.mit.edu (outgoing-auth-1.mit.edu [18.9.28.11]) by smtp1.osuosl.org (Postfix) with ESMTPS id AA7F48161D; Wed, 19 Jan 2022 07:32:51 +0000 (UTC) Received: from mail-lf1-f47.google.com (mail-lf1-f47.google.com [209.85.167.47]) (authenticated bits=0) (User authenticated as jlrubin@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 20J7Wmwq003089 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NOT); Wed, 19 Jan 2022 02:32:49 -0500 Received: by mail-lf1-f47.google.com with SMTP id br17so5723139lfb.6; Tue, 18 Jan 2022 23:32:49 -0800 (PST) X-Gm-Message-State: AOAM531DZA2JYI15l2cAIdaXCemMAHJlDgEJVE5JOS6kNboCIrvKQAhD kY6xcA0yPQt+f2mHUwh1BkBpuGU4Qn55ZnHfYU4= X-Google-Smtp-Source: ABdhPJwsUnJOs0PQL1xxnkzKyBeXxl+nSuaBSWR1tB+H2SoI6vpi5Oekx846Bg6ZmYD3BxxUQSEDsrZw2eEcS2o7YIw= X-Received: by 2002:a05:651c:904:: with SMTP id e4mr23696564ljq.198.1642577567773; Tue, 18 Jan 2022 23:32:47 -0800 (PST) MIME-Version: 1.0 References: In-Reply-To: From: Jeremy Date: Tue, 18 Jan 2022 23:32:36 -0800 X-Gmail-Original-Message-ID: Message-ID: To: Billy Tetrud Content-Type: multipart/alternative; boundary="0000000000007179f805d5ea64ed" Cc: Bitcoin Protocol Discussion , lightning-dev Subject: Re: [bitcoin-dev] [Pre-BIP] Fee Accounts X-BeenThere: bitcoin-dev@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Bitcoin Protocol Discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 19 Jan 2022 07:32:54 -0000 --0000000000007179f805d5ea64ed Content-Type: text/plain; charset="UTF-8" Ah my bad i misread what you were saying as being about SIGHASH_BUNDLE like proposals. For what you're discussing, I previously proposed https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2020-September/018168.html which is similar. The benefit of the OP_VER output is that SIGHASH_EXTERNAL has the issue that unless you're binding a WTXID (which is maybe too specific?) then you can have fee bumping cycles. Doing OP_VER output w/ TXID guarantees that you are acyclic. The difference between a fee account and this approach basically boils down to the impact on e.g. reorg stability, where the deposit/withdraw mechanism is a bit more "robust" for reorderings in reorgs than the in-band transaction approach, although they are very similar. -- @JeremyRubin On Tue, Jan 18, 2022 at 8:53 PM Billy Tetrud wrote: > > because you make transactions third party malleable it becomes > possible to bundle and unbundle transactions. > > What I was suggesting doesn't make it possible to malleate someone else's > transaction. I guess maybe my proposal of using a sighash flag might have > been unclear. Imagine it as a script opcode that just says "this > transaction must be mined with this other transaction" - the only > difference being that you can use any output with any encumberance as an > input for fee bumping. It doesn't prevent the original transaction from > being mined on its own. So adding junk inputs would be no more of a problem > than dust attacks already are. It would be used exactly like cpfp, except > it doesn't spend the parent. > > I don't think what I was suggesting is as different from your proposal. > All the problems of fee revenue optimization and feerate rules that you > mentioned seem like they'd also exist for your proposal, or for cpfp. Let > me know if I should clarify further. > > On Tue, Jan 18, 2022 at 8:51 PM Jeremy wrote: > >> The issue with sighash flags is that because you make transactions third >> party malleable it becomes possible to bundle and unbundle transactions. >> >> This means there are circumstances where an attacker could e.g. see your >> txn, and then add a lot of junk change/inputs + 25 descendants and strongly >> anchor your transaction to the bottom of the mempool. >> >> because of rbf rules requiring more fee and feerate, this means you have >> to bump across the whole package and that can get really messy. >> >> more generally speaking, you could imagine a future where mempools track >> many alternative things that might want to be in a transaction. >> >> suppose there are N inputs each with a weight and an amount of fee being >> added and the sighash flags let me pick any subset of them. However, for a >> txn to be standard it must be < 100k bytes and for it to be consensus < >> 1mb. Now it is possible you have to solve a knapsack problem in order to >> rationally bundle this transaction out of all possibilities. >> >> This problem can get even thornier, suppose that the inputs I'm adding >> themselves are the outputs of another txn in the mempool, now i have to >> track and propagate the feerates of that child back up to the parent txn >> and track all these dependencies. >> >> perhaps with very careful engineering these issues can be tamed. however >> it seems with sponsors or fee accounts, by separating the pays-for from the >> participates-in concerns we can greatly simplify it to something like: >> compute effective feerate for a txn, including all sponsors that pay more >> than the feerate of the base txn. Mine that txn and it's subsidies using >> the normal algo. If you run out of space, all subsidies are same-sized so >> just take the ones that pay the highest amount up until the added marginal >> feerate is less than the next eligible txn. >> >> >> -- >> @JeremyRubin >> >> >> >> On Tue, Jan 18, 2022 at 6:38 PM Billy Tetrud >> wrote: >> >>> I see, its not primarily to make it cheaper to append fees, but also >>> allows appending fees in cases that aren't possible now. Is that right? I >>> can certainly see the benefit of a more general way to add a fee to any >>> transaction, regardless of whether you're related to that transaction or >>> not. >>> >>> How would you compare the pros and cons of your account-based approach >>> to something like a new sighash flag? Eg a sighash flag that says "I'm >>> signing this transaction, but the signature is only valid if mined in the >>> same block as transaction X (or maybe transactions LIST)". This could be >>> named SIGHASH_EXTERNAL. Doing this would be a lot more similar to other >>> bitcoin transactions, and no special account would need to be created. Any >>> transaction could specify this. At least that's the first thought I would >>> have in designing a way to arbitrarily bump fees. Have you compared your >>> solution to something more familiar like that? >>> >>> On Tue, Jan 18, 2022 at 11:43 AM Jeremy wrote: >>> >>>> Can you clarify what you mean by "improve the situation"? >>>> >>>> There's a potential mild bytes savings, but the bigger deal is that the >>>> API should be much less vulnerable to pinning issues, fix dust leakage for >>>> eltoo like protocols, and just generally allow protocol designs to be fully >>>> abstracted from paying fees. You can't easily mathematically quantify API >>>> improvements like that. >>>> -- >>>> @JeremyRubin >>>> >>>> >>>> >>>> On Tue, Jan 18, 2022 at 8:13 AM Billy Tetrud >>>> wrote: >>>> >>>>> Do you have any back-of-the-napkin math on quantifying how much this >>>>> would improve the situation vs existing methods (eg cpfp)? >>>>> >>>>> >>>>> >>>>> On Sat, Jan 1, 2022 at 2:04 PM Jeremy via bitcoin-dev < >>>>> bitcoin-dev@lists.linuxfoundation.org> wrote: >>>>> >>>>>> Happy new years devs, >>>>>> >>>>>> I figured I would share some thoughts for conceptual review that have >>>>>> been bouncing around my head as an opportunity to clean up the fee paying >>>>>> semantics in bitcoin "for good". The design space is very wide on the >>>>>> approach I'll share, so below is just a sketch of how it could work which >>>>>> I'm sure could be improved greatly. >>>>>> >>>>>> Transaction fees are an integral part of bitcoin. >>>>>> >>>>>> However, due to quirks of Bitcoin's transaction design, fees are a >>>>>> part of the transactions that they occur in. >>>>>> >>>>>> While this works in a "Bitcoin 1.0" world, where all transactions are >>>>>> simple on-chain transfers, real world use of Bitcoin requires support for >>>>>> things like Fee Bumping stuck transactions, DoS resistant Payment Channels, >>>>>> and other long lived Smart Contracts that can't predict future fee rates. >>>>>> Having the fees paid in band makes writing these contracts much more >>>>>> difficult as you can't merely express the logic you want for the >>>>>> transaction, but also the fees. >>>>>> >>>>>> Previously, I proposed a special type of transaction called a >>>>>> "Sponsor" which has some special consensus + mempool rules to allow >>>>>> arbitrarily appending fees to a transaction to bump it up in the mempool. >>>>>> >>>>>> As an alternative, we could establish an account system in Bitcoin as >>>>>> an "extension block". >>>>>> >>>>>> *Here's how it might work:* >>>>>> >>>>>> 1. Define a special anyone can spend output type that is a "fee >>>>>> account" (e.g. segwit V2). Such outputs have a redeeming key and an amount >>>>>> associated with them, but are overall anyone can spend. >>>>>> 2. All deposits to these outputs get stored in a separate UTXO >>>>>> database for fee accounts >>>>>> 3. Fee accounts can sign only two kinds of transaction: A: a fee >>>>>> amount and a TXID (or Outpoint?); B: a withdraw amount, a fee, and >>>>>> an address >>>>>> 4. These transactions are committed in an extension block merkle >>>>>> tree. While the actual signature must cover the TXID/Outpoint, the >>>>>> committed data need only cover the index in the block of the transaction. >>>>>> The public key for account lookup can be recovered from the message + >>>>>> signature. >>>>>> 5. In any block, any of the fee account deposits can be: released >>>>>> into fees if there is a corresponding tx; consolidated together to reduce >>>>>> the number of utxos (this can be just an OP_TRUE no metadata needed); or >>>>>> released into fees *and paid back* into the requested withdrawal key >>>>>> (encumbering a 100 block timeout). Signatures must be unique in a block. >>>>>> 6. Mempool logic is updated to allow attaching of account fee spends >>>>>> to transactions, the mempool can restrict that an account is not allowed >>>>>> more spend more than it's balance. >>>>>> >>>>>> *But aren't accounts "bad"?* >>>>>> >>>>>> Yes, accounts are bad. But these accounts are not bad, because any >>>>>> funds withdrawn from the fee extension are fundamentally locked for 100 >>>>>> blocks as a coinbase output, so there should be no issues with any series >>>>>> of reorgs. Further, since there is no "rich state" for these accounts, the >>>>>> state updates can always be applied in a conflict-free way in any order. >>>>>> >>>>>> >>>>>> *Improving the privacy of this design:* >>>>>> >>>>>> This design could likely be modified to implement something like >>>>>> Tornado.cash or something else so that the fee account paying can be >>>>>> unlinked from the transaction being paid for, improving privacy at the >>>>>> expense of being a bit more expensive. >>>>>> >>>>>> Other operations could be added to allow a trustless mixing to be >>>>>> done by miners automatically where groups of accounts with similar values >>>>>> are trustlessly split into a common denominator and change, and keys are >>>>>> derived via a verifiable stealth address like protocol (so fee balances can >>>>>> be discovered by tracing the updates posted). These updates could also be >>>>>> produced by individuals rather than miners, and miners could simply honor >>>>>> them with better privacy. While a miner generating an update would be able >>>>>> to deanonymize their mixes, if you have your account mixed several times by >>>>>> independent miners that could potentially add sufficient privacy. >>>>>> >>>>>> The LN can also be used with PTLCs to, in theory, have another >>>>>> individual paid to sponsor a transaction on your behalf only if they reveal >>>>>> a valid sig from their fee paying account, although under this model it's >>>>>> hard to ensure that the owner doesn't pay a fee and then 'cancel' by >>>>>> withdrawing the rest. However, this could be partly solved by using >>>>>> reputable fee accounts (reputation could be measured somewhat >>>>>> decentralized-ly by longevity of the account and transactions paid for >>>>>> historically). >>>>>> >>>>>> *Scalability* >>>>>> >>>>>> This design is fundamentally 'decent' for scalability because adding >>>>>> fees to a transaction does not require adding inputs or outputs and does >>>>>> not require tracking substantial amounts of new state. >>>>>> >>>>>> Paying someone else to pay for you via the LN also helps make this >>>>>> more efficient if the withdrawal issues can be fixed. >>>>>> >>>>>> *Lightning:* >>>>>> >>>>>> This type of design works really well for channels because the >>>>>> addition of fees to e.g. a channel state does not require any sort of >>>>>> pre-planning (e.g. anchors) or transaction flexibility (SIGHASH flags). >>>>>> This sort of design is naturally immune to pinning issues since you could >>>>>> offer to pay a fee for any TXID and the number of fee adding offers does >>>>>> not need to be restricted in the same way the descendant transactions would >>>>>> need to be. >>>>>> >>>>>> *Without a fork?* >>>>>> >>>>>> This type of design could be done as a federated network that bribes >>>>>> miners -- potentially even retroactively after a block is formed. That >>>>>> might be sufficient to prove the concept works before a consensus upgrade >>>>>> is deployed, but such an approach does mean there is a centralizing layer >>>>>> interfering with normal mining. >>>>>> >>>>>> >>>>>> Happy new year!! >>>>>> >>>>>> Jeremy >>>>>> >>>>>> -- >>>>>> @JeremyRubin >>>>>> >>>>>> _______________________________________________ >>>>>> bitcoin-dev mailing list >>>>>> bitcoin-dev@lists.linuxfoundation.org >>>>>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >>>>>> >>>>> --0000000000007179f805d5ea64ed Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Ah my bad i misread what = you were saying as being about SIGHASH_BUNDLE like proposals.
<= div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif= ;font-size:small;color:#000000">
For what you're discussing, I previously p= roposed=C2=A0https://lists.linuxfoundation.org/pipermai= l/bitcoin-dev/2020-September/018168.html which is similar.

The benefit of the OP_VER output is t= hat SIGHASH_EXTERNAL has the issue that unless you're binding a WTXID (= which is maybe too specific?) then you can have fee bumping cycles. Doing O= P_VER output w/ TXID guarantees that you are acyclic.

The difference between a fee account and this = approach basically boils down to the impact on e.g. reorg stability, where = the deposit/withdraw mechanism is a bit more "robust" for reorder= ings in reorgs than the in-band transaction approach, although they are ver= y similar.

--
<= /div>

On Tue, Jan 18, 2022 at 8:53 PM Billy Tetrud <billy.tetrud@gmail.com> wrote:
>=C2=A0 bec= ause you make transactions third party malleable it becomes possible to bun= dle and unbundle transactions.

What I was sugges= ting doesn't make it possible to malleate someone else's transactio= n.=C2=A0I guess maybe my proposal of using a sighash flag might have be= en unclear. Imagine it as a script opcode that just says "this transac= tion=C2=A0must be mined with this other transaction" - the only differ= ence being that you can use any output with any encumberance=C2=A0as an inp= ut for fee=C2=A0bumping. It doesn't prevent the original transaction fr= om being mined on its own. So adding junk inputs would be no more of a prob= lem than dust attacks already are. It would be used exactly like cpfp, exce= pt it doesn't spend the parent.=C2=A0

= I don't think what I was suggesting is as different from your proposal.= All the problems of fee revenue optimization and feerate rules that you me= ntioned seem like they'd also exist for your proposal, or for cpfp. Let= me know if I should clarify further.=C2=A0

On Tue, Jan 18, 202= 2 at 8:51 PM Jeremy <jlrubin@mit.edu> wrote:
The issue with sighash flags is that b= ecause you make transactions third party malleable it becomes possible to b= undle and unbundle transactions.
<= br>
This means there are circumsta= nces where an attacker could e.g. see your txn, and then add a lot of junk = change/inputs=C2=A0+ 25 descendants and strongly anchor your transaction to= the bottom of the mempool.

because of rbf rules requiring more= fee and feerate, this means you have to bump across the whole package and = that can get really messy.

more generally speaking, you could i= magine a future where mempools track many alternative things that might wan= t to be in a transaction.

suppose there are N inputs each with = a weight and an amount of fee being added and the sighash flags let me pick= any subset of them. However, for a txn to be standard it must be < 100k= bytes and for it to be consensus < 1mb. Now it is possible you have to = solve a knapsack problem in order to rationally bundle this transaction out= of all possibilities.

<= div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif= ;font-size:small;color:rgb(0,0,0)">This problem can get even thornier, supp= ose that the inputs I'm adding themselves are the outputs of another tx= n in the mempool, now i have to track and propagate the feerates of that ch= ild back up to the parent txn and track all these dependencies.

perhaps with very careful engineering these issues can be tamed. however = it seems with sponsors or fee accounts, by separating the pays-for from the= participates-in concerns we can greatly simplify it to something like: com= pute effective feerate for a txn, including all sponsors that pay more than= the feerate of the base txn. Mine that txn and it's subsidies using th= e normal algo. If you run out of space, all subsidies are same-sized so jus= t take the ones that pay the highest amount up until the added marginal fee= rate is less than the next eligible txn.




On Tue, Jan 18, 2022 at 6:= 38 PM Billy Tetrud <billy.tetrud@gmail.com> wrote:
I see, its not primarily to make it cheaper to append fees, b= ut also allows appending fees in cases that aren't possible now. Is tha= t right? I can certainly see the benefit of a more general way to add a fee= to any transaction, regardless of whether you're related to that trans= action or not.=C2=A0

How would you compare the pros and = cons of your account-based approach to something like a new sighash flag? E= g a sighash flag that says "I'm signing this transaction, but the = signature is only valid if mined in the same block as transaction=C2=A0X (o= r maybe transactions LIST)". This could be named SIGHASH_EXTERNAL. Doi= ng this would be a lot more similar to other bitcoin transactions, and no s= pecial account would need to be created. Any transaction could specify this= . At least that's the first thought I would have in designing a way to = arbitrarily bump fees. Have you compared your solution to something more fa= miliar like that?

On Tue, Jan 18, 2022 at 11:43 AM Jeremy <jlrubin@mit.edu> wrote= :
Can you clarify what you mean by "improve the situation"?

There's a potential mild bytes savings, but the bigger deal = is that the API should be much less vulnerable to pinning issues, fix dust = leakage for eltoo like protocols, and just generally allow protocol designs= to be fully abstracted from paying fees. You can't easily mathematical= ly quantify=C2=A0API improvements=C2=A0like that.


On Tue, Jan 18, 2022 at 8:13 AM Bi= lly Tetrud <= billy.tetrud@gmail.com> wrote:
Do you have any back-of-the-napkin math on quantifying=C2=A0how = much this would improve the situation vs existing methods (eg cpfp)?
<= div>


On Sat, Jan 1, 2022 at 2:04= PM Jeremy via bitcoin-dev <bitcoin-dev@lists.linuxfoundation.org>= ; wrote:
Happy new years devs,

I figured I would share som= e thoughts for conceptual review that have been bouncing around my head as = an opportunity to clean up the fee paying semantics in bitcoin "for go= od". The design space is very wide on the approach I'll share, so = below is just a sketch of how it could work which I'm sure could be imp= roved greatly.

Transaction fees are an integral part of bitcoin= .

However, due to quirks of Bitcoin's transaction design, f= ees are a part of the transactions that they occur in.

While th= is works in a "Bitcoin 1.0" world, where all transactions are sim= ple on-chain transfers, real world use of Bitcoin requires support for thin= gs like Fee Bumping stuck transactions, DoS resistant Payment Channels, and= other long lived Smart Contracts that can't predict future fee rates. = Having the fees paid in band makes writing these contracts much more diffic= ult as you can't merely express the logic you want for the transaction,= but also the fees.

Previously, I proposed a special type of tr= ansaction called a "Sponsor" which has some special consensus=C2= =A0+ mempool rules to allow arbitrarily appending fees to a transaction to = bump it up in the mempool.

As an alternative, we could establis= h an account system in Bitcoin as an "extension block".

Here's how it might work:

1. Define a special any= one can spend output type that is a "fee account" (e.g. segwit V2= ). Such outputs have a redeeming key and an amount associated with them, bu= t are overall anyone can spend.
2.= All deposits to these outputs get stored in a separate UTXO database for f= ee accounts
3. Fee accounts can si= gn only two kinds of transaction: A: a fee amount and a TXID (or Outpoint?)= ; B: a withdraw amount, a fee, and an=C2=A0address
4. These transactions are committed in an extension block = merkle tree. While the actual signature must cover the TXID/Outpoint, the c= ommitted data need only cover the index in the block of the transaction. Th= e public key for account lookup can be recovered from the message=C2=A0+ si= gnature.
5. In any block, any of t= he fee account deposits can be: released into fees if there is a correspond= ing tx; consolidated together to reduce the number of utxos (this can be ju= st an OP_TRUE no metadata needed); or released into fees *and paid back* in= to the requested withdrawal key (encumbering a 100 block timeout). Signatur= es must be unique in a block.
6. M= empool logic is updated to allow attaching of account fee spends to transac= tions, the mempool can restrict that an account is not allowed more spend m= ore than it's balance.

But aren't accounts "bad= "?

Yes, accounts are bad. But these accounts are not= bad, because any funds withdrawn from the fee extension are fundamentally = locked for 100 blocks as a coinbase output, so there should be no issues wi= th any series of reorgs. Further, since there is no "rich state" = for these accounts, the state updates can always be applied in a conflict-f= ree way in any order.


Improving the privacy of this design:

This design c= ould likely be modified to implement something like Tornado.cash or somethi= ng else so that the fee account paying can be unlinked from the transaction= being paid for, improving privacy at the expense of being a bit more expen= sive.

Other operations could be added to allow a trustless mixi= ng to be done by miners automatically where groups of accounts with similar= values are trustlessly =C2=A0split into a common denominator and change, a= nd keys are derived via a verifiable stealth address like protocol (so fee = balances can be discovered by tracing the updates posted). These updates co= uld also be produced by individuals rather than miners, and miners could si= mply honor them with better privacy. While a miner generating an update wou= ld be able to deanonymize their mixes, if you have your account mixed sever= al times by independent miners that could potentially add sufficient privac= y.

The LN can also be used with PTLCs to, in theory, have anoth= er individual paid to sponsor a transaction on your behalf only if they rev= eal a valid sig from their fee paying account, although under this model it= 's hard to ensure that the owner doesn't pay a fee and then 'ca= ncel' by withdrawing the rest. However, this could be partly solved by = using reputable fee accounts (reputation could be measured somewhat decentr= alized-ly by longevity of the account and transactions paid for historicall= y).

Scalability

This design is funda= mentally 'decent' for scalability because adding fees to a transact= ion does not require adding inputs or outputs and does not require tracking= substantial amounts of new state.

Paying someone else to pay = for you via the LN also helps make this more efficient if the withdrawal is= sues can be fixed.

Lightning:

This ty= pe of design works really well for channels because the addition of fees to= e.g. a channel state does not require any sort of pre-planning (e.g. ancho= rs) or transaction flexibility (SIGHASH flags). This sort of design is natu= rally immune to pinning issues since you could offer to pay a fee for any T= XID and the number of fee adding offers does not need to be restricted in t= he same way the descendant transactions would need to be.

= Without a fork?

This type of design could be done as a fede= rated network that bribes miners -- potentially even retroactively after a = block is formed. That might be sufficient to prove the concept works before= a consensus upgrade is deployed, but such an approach does mean there is a= centralizing layer interfering with normal mining.


<= div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-serif= ;font-size:small;color:rgb(0,0,0)">Happy new year!!

Jeremy
_______________________________________________
bitcoin-dev mailing list
= bitcoin-dev@lists.linuxfoundation.org
https://lists.linuxfoundation.org/mail= man/listinfo/bitcoin-dev
--0000000000007179f805d5ea64ed--