[bitcoin-dev] [Pre-BIP] Motivating Address type for OP_RETURN

[Jeremy]

I guess in the interest of being clear; I don't particularly want a
OP_RETURN address either, they're just annoying to program around, and they
exist historically, as well as perhaps in the future.

Maybe people will start using the annex space to add any metadata required?
E.g. stealth addresses. I kinda hope not, but probably will be proposed as
a SF since it's much cheaper (witness + no amount) and per-input vs. per-tx.

It's interesting that they can be created with any length... i guess any
script can be an op return if you make it long enough...
--
@JeremyRubin <https://twitter.com/JeremyRubin>
<https://twitter.com/JeremyRubin>


On Sat, Apr 24, 2021 at 3:00 PM David A. Harding <dave at dtrt.org> wrote:

> On Sat, Apr 24, 2021 at 01:05:25PM -0700, Jeremy wrote:
> > I meant the type itself is too wide, not the length of the value. As in
> > Script can represent things we know nothing about.
>
> I guess I still don't understand your concern, then.  If script can
> represent things we know nothing about, then script commitments such as
> P2SH, P2WSH, and P2TR also represent things we know nothing about.  All
> you know is what container format they used.  For P2PK, bare multisig,
> OP_RETURN, and other direct uses of scriptPubKey, that container format
> is "bare" (or whatever you want to call it).
>
> > Btw: According to... Oh wait... You?
> >
> https://bitcoin.stackexchange.com/questions/35878/is-there-a-maximum-size-of-a-scriptsig-scriptpubkey
> > the max size is 10k bytes.
>
> I'm not sure what I knew at the time I wrote that answer, but the 10,000
> byte limit is only applied when EvalScript is run, which only happens
> when the output is being spent.  I've appended to this email a
> demonstration of creating a 11,000 byte OP_RETURN on regtest (I tried
> 999,000 bytes but ran into problems with bash's maximum command line
> length limit).  I've updated the answer to hopefully make it more
> correct.
>
> > Is it possible/easy to, say, using bech32m make an inappropriate message
> in
> > the address? You'd have to write the message, then see what it decodes to
> > without checking, and then re encode? I guess this is worse than hex?
>
> If someone wants to abuse bech32m, I suspect they'll do it the same way
> people have abused base58check[1], by using the address format's
> alphabet directly.  E.g., you compose your message using only
> the characters qpzry9x8gf2tvdw0s3jn54khce6mua7l and then append
> the appropriate checksum.
>
> [1]
> https://en.bitcoin.it/wiki/P2SH%C2%B2#The_problem:_storing_data_in_hashes
>
> > But it seems this is a general thing... If you wanted an inappropriate
> > message you could therefore just use bech32m addressed outputs.
>
> Yes, and people have done that with base58check.  IsStandard OP_RETURN
> attempts to minimize that abuse by being cheaper in two ways:
>
> 1. More data allowed in scriptSig, e.g. 80 byte payload (81 actually, I
>    think) for OP_RETURN versus 40 bytes for a BIP141 payload.
>    Maximizing payload size better amortizes the overhead cost of the
>    containing transaction and the output's nValue field.
>
> 2. Exemption from the dust limit.  If you use a currently defined
>    address type, the nValue needs to pay at least a few thousand nBTC
>    (few hundred satoshis), about $0.15 USD minimum at $50k USD/BTC.  For
>    OP_RETURN, the nValue can be 0, so there's no additional cost beyond
>    normal transaction relay fees.
>
> Although someone creating an OP_RETURN up to ~1 MB with miner support
> can bypass the dust limit, the efficiency advantage remains no matter
> what.
>
> > One of the nice things is that the current psbt interface uses a blind
> > union type whereby the entires in an array are either [address, amount]
> or
> > ["data", hex]. Having an address type would allow more uniform handling,
> > which is convenient for strongly typed RPC bindings (e.g. rust bitcoin
> uses
> > a hashmap of address to amount so without a patch you can't create op
> > returns).
>
> I don't particularly care how the data in PSBTs are structured.  My mild
> opposition was to adding code to the wallet that exposes everyday users
> to OP_RETURN addresses.
>
> > I would much prefer to not have to do this in a custom way, as opposed
> > to a way which is defined in a standard manner across all software
> > (after all, that's the point of standards).
>
> I'm currently +0.1 on the idea of an address format of OP_RETURN, but I
> want to make sure this isn't underwhelmingly motivated or will lead to a
> resurgence of block chain graffiti.
>
> -Dave
>
> ## Creating an 11,000 byte OP_RETURN
>
> $ bitcoind -daemon -regtest -acceptnonstdtxn
> Bitcoin Core starting
>
> $ bitcoin-cli -regtest -generate 101
> {
>   "address": "bcrt1qh9uka5z040vx2rc3ltz3tpwmq4y2mt0eufux9r",
>   "blocks": [
> [...]
> }
>
> $ bitcoin-cli -regtest send '[{"data": "'$( dd if=/dev/zero bs=1000
> count=11 | xxd -g0 -p | tr -d '\n' )'"}]'
> 11+0 records in
> 11+0 records out
> 11000 bytes (11 kB, 11 KiB) copied, 0.000161428 s, 68.1 MB/s
> {
>   "txid":
> "ef3d396c7d21914a2c308031c9ba1857694fc33df71f5a349b409ab3406dab51",
>   "complete": true
> }
>
> $ bitcoin-cli -regtest getrawmempool
> [
>   "ef3d396c7d21914a2c308031c9ba1857694fc33df71f5a349b409ab3406dab51"
> ]
>
> $ bitcoin-cli -regtest -generate 1
> {
>   "address": "bcrt1qlzjd90tkfkr09m867zxhte9rqd3t03wc5py5zh",
>   "blocks": [
>     "2986e9588c5bd26a629020b1ce8014d1f4ac9ac19106d216d3abb3a314c5604b"
>   ]
> }
>
> $bitcoin-cli -regtest getblock
> 2986e9588c5bd26a629020b1ce8014d1f4ac9ac19106d216d3abb3a314c5604b 2 | jq
> .tx[1].txid
> "ef3d396c7d21914a2c308031c9ba1857694fc33df71f5a349b409ab3406dab51"
>
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