From: Chris Stewart <stewart.chris1234@gmail.com>
To: jeremy <jeremy.l.rubin@gmail.com>
Cc: Bitcoin Development Mailing List <bitcoindev@googlegroups.com>
Subject: Re: [bitcoindev] [BIP-0054] 64-Byte Transactions and Potential Legitimate Uses
Date: Sat, 2 May 2026 10:26:15 -0500 [thread overview]
Message-ID: <CAGL6+mGeqx8TvWSfSg_FdrbHVy+3Sk5VmQ+_WPjGjhXbp=LiBA@mail.gmail.com> (raw)
In-Reply-To: <123e5545-2eda-4eca-9532-4f4cea2b83ecn@googlegroups.com>
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I do concede your point that witness stripping isn't well understood by the
general community. Here is a writeup I did for readers of the mailing list
that may not understand what Jeremy is talking about the characteristics of
a 64 byte transaction[0]. There is a big distinction between pre-segwit 64
byte transactions and segwit 64 byte transactions.
> A transaction that donates to a future miner from a segwit (any version)
output via a spend to something like <512> OP_CSV (-> push2 bytes 512 csv
-> 0x02 0x00 0x02 0xb2)
I find this confusing. Can you give 2 hex encoded transactions (funding
transaction, spending transaction) that do this? regtest is fine, i can
just decode locally.
Splitting hairs semantically if understand the transactions you are
proposing above, "donating" to a "future miner" i.e. sending money to *anyone
(not a specific someone)* in the future that can mine a block - doesn't
seem much different to me than "anyone can spend the funds". I'll await
your transactions though in the case that I am missing something.
[0] -
https://delvingbitcoin.org/t/great-consensus-cleanup-revival/710/73?u=chris_stewart_5
On Fri, May 1, 2026 at 4:15 PM jeremy <jeremy.l.rubin@gmail.com> wrote:
> For fun, let's start with a pop-quiz:
>
> Select all that apply: There can exist a transaction of ___ bytes
> serialized size that BIP-0054's 64-byte restriction invalidates:
>
> A) 64 Bytes
> B) 0 Bytes
> C) 1.5MB
> D) 32 Bytes
> E) 5MB
>
>
> The answer is A, 64 Bytes, and -- perhaps surprisingly -- C, 1.5MB.
>
> Why is this the case?
>
> BIP-0054 uses the term 64-byte transaction, but defines it as follows:
>
> *> Transactions whose witness-stripped serialized size is exactly 64 bytes
> are invalid.*
>
> In a [personally run] straw-poll of devs at a recent conference, no-one
> knew this precise edge condition or that the transactions could have a
> meaningful witness. For clarity, the restriction on bytes is on
> INVALID_TX_NONWITNESS_SIZE, not on the size with Witness.
>
> Therefore, it is more accurate to refer to this in all sentences
> throughout the BIP as:
>
> *> transactions with exactly 64 bytes of non-witness data*,
>
> due to the propensity for confusion.
>
> BIP-0054 also makes a comment that the transactions it invalidates are
> essentially useless:
>
>
> *> 64-byte transactions can only contain a scriptPubKey that lets anyone
> spend the funds, or one that burns them.*
>
> This is not strictly correct. Here are a few examples of current and
> future uses for 64-byte transactions:
>
> *Current Uses:*
> - A transaction that donates to a future miner from a segwit (any version)
> output via a spend to something like <512> OP_CSV (-> push2 bytes 512 csv
> -> 0x02 0x00 0x02 0xb2)
> - That same output which is used as a connector output for things that
> should be claimed by a miner at a future time
> - Pay-to-Anchor / ephemeral anchor outputs -- while typically p2a is for
> txns you want to add a subsidy ability, a 64-byte txn could be used to shim
> a keyed anchor to a p2a output after a certain delay.
>
> *Future Uses:*
> - Future work which might use output scripts for e.g. Transaction Sponsor
> encodings
> - Future covenants work which encodes time-of-creation run scripts that
> e.g. quine an input; possibly in conjunction with sponsors
> - Future where we have expensive reusable PQ or Contract public keys that
> are posted once and referred to by index
>
>
> While, in a sense, current uses are much more concerning than future uses,
> with introspection opcodes, it might create substantive additional
> complexity to ensure that there is always a valid way to add a padding byte
> without upsetting a state machine.
>
> As there are now documented use cases for 64-byte transactions that this
> proposal makes more difficult to do, I recommend replacing the text in the
> BIP that says
>
>
> *> 64-byte transactions can only contain a scriptPubKey that lets anyone
> spend the funds, or one that burns them. *
> With something like:
>
> *> There are documented use cases for 64-byte transactions that this
> proposal makes more difficult to cleanly do, but we do not believe these
> use cases will ever be valuable or worth protecting.*
>
> Or a more accurate reflection of the BIP-0054 authors' opinion.
>
> Jeremy
>
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next prev parent reply other threads:[~2026-05-02 15:56 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-01 21:14 [bitcoindev] [BIP-0054] 64-Byte Transactions and Potential Legitimate Uses jeremy
2026-05-01 22:03 ` eric
2026-05-14 13:50 ` 'Antoine Poinsot' via Bitcoin Development Mailing List
2026-05-02 5:29 ` Anthony Towns
2026-05-02 15:26 ` Chris Stewart [this message]
2026-05-02 18:09 ` jeremy
2026-05-06 11:10 ` 'Antoine Poinsot' via Bitcoin Development Mailing List
2026-05-06 21:35 ` jeremy
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