Topic: BIP 322 draft design and improvement thread - page 2. (Read 890 times)

I am not an expert in the various use-cases I stated for this, so I will make no attempt to reply to any of that.


No, this was in older revisions of BIP322 as a TODO, one of the unaddressed "edge cases" if you want to call it that.


Yeah well if I don't do something about it (read: write specifications for dealing with it, write code that uses it, maybe tell Blockchain Commons that there are people who are actually interested in helping out with their BIP322 efforts), then nobody's going to do anything about related problems.

Because everyone has this kind of attitude that "If nobody replies to my proposals, that must mean they are garbage" - which is wrong because perhaps it's a good idea but the decision-makers for that particular proposal haven't seen it yet  (It is worth mentioning that I have no clue if Kalle has seen a single one of my mailing list or Github comments). It's thankless work, because for all the pitchforks thrown in your general direction, you get virtually no credit at all - but I'm not here for credit, I'm here for progress and advancement of Bitcoin. And it's the only reason why I'm still continuing these efforts.

And, if you don't do anything, progress grinds to a halt [and, if this non-activity extends to maintenance, then you don't just have a "maintenance-mode" project, you end up with a completely abandoned project].

In this space, and any other truly open-source space, all the work is decentalized. Take that away and you don't truly have an open-source project anymore - at worst you have some quasi-OSS like Microsoft's and Google's stuff (source code is accessible, but suggestions and final decisions are made behind closed-doors).


Their definition of "delegation" is completely different from the one listed in the BIP (although incidentially, the solutions are both loosely derived from the same mailing list post):

- CoinGeek's is: "Alice allows Bob to spend her UTXO on-chain"
- Mine is: "Alice hides her UTXOs behind an invalid, off-chain output which can sign a BIP322 transaction"

There is a huge difference here. It is indeed foolish, and very risky, to design some protocol that allows other people to spend your money. It would be no better than a smart contract. In fact, their's is a smart contract, whereas I have explicitly stated that my schema is not one.

This "signer delegation" that I'm talking about in previous posts, does not allow a person to spend anything, it hides the original UTXOs from the signature and only allows other people to sign a message on their own behalf.

All this without revealing any private keys to anybody - the delegated has to solve a challenge script to sign the message.


In 99% of real-world cases there is no need for multiple chains of delegations, a single delegation transaction will suffice. Once you read the pesudonym example below, you'd see that the 1% cases would be like "making an alias for an alias for a person" (e.g. suppose Satoshi makes a new nickname).

BIP322 signing has always been P2P, there is no central entity involved.


Again, there is no delegation of authority from one person to another in this scheme. We are merely hiding the address(es) behind some operation that combines them together to make a new address. The TODO says this is for "better CoinJoin and Lightning compatibility" - although it is possibly redundant according to your statements about these two technologies, it has to be introduced in a way that they can make use of BIP322 signed messages if they want to in the future. A third technology could be invented in the future on top of CoinJoin or LN that requires BIP322 signatures for correct operation, that's why.

In this sense, it's not really "delegation" in the traditional sense at all - we're just hiding the original signers' identity behind a pseudonym e.g. "Satoshi Nakamoto".

True this scheme is not perfect - it assumes a trusted public - because anybody can claim the pseudonym i.e. claim to own the delegated address - so in the example for pseudonym this would be solved by introducing a GPG key alongside the pseudonym's posts - I'm working on a similar way to solve that particular problem with this proposal.


Actually, the BIP never mentioned the word "person" in that TODO, so this was merely an assumption that I made, and this never really made any sense until I thought about this problem and realized that it's not attempting to delegate control to different people, but to different aliases.


You almost got it, but the signer attaches the delegation tx to the "to_spend" tx. The Message/Address/Signature tuple contains the witness stack for unlocking the sole output of the "to_delegate" tx.

Currently, only "to_spend" is verified by others because ther is no info to verify the delegation tx. I'm going to admit that this is a problem that needs to be solved, by giving the alias its own keypair i.e. identity (this will mean using P2WPKH instead of P2WSH).


On the web pages of course. Legacy signed messages were never stored in the blockchain anyway.

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TL;DR

This is not truly "delegation" as other people call it, but the problem of hiding of signer's identity behind a pseudonym, so that he/she cannot be fingerprinted and monitored by spies.

Why did BIP322 call it that, then? I don't know. But this seems to be the meaning that is implied.

Look, I know that you don't like BIP322 because of the way it looks, but by any means, somebody has to make a message signing solution that not only works technically, but has the general consensus of all technical people.

edited for spelling

edit 2: In fact, in light of this, I can simplify the proposal a little bit:

- Instead of a P2WSH output, "to_delegate" creates a single, standard P2WPKH output withits own keypair.
- In a "Full with UTXOs" signed message, the outputs to be proven are already inside the "to_sign" inputs - meaning they are fully included in the signature and can be verified - if any of these inputs want to hide behind an alias, they only have to generate a new keypair. Then make a "to_delegate" transaction which has:
-- an invalid input
-- one or more UTXOs as input
-- a single P2WPKH output with the generated keypair
Which resembles a normal transaction but it's invalid because of the invalid input. This specific tx is not verified as that would be equivalent to "revealing the identity of the alias".

Now "to_sign" transactions can have this alias UTXO as an input instead of all those UTXOs that want to hide their identity.

I do not believe it is possible to fully prove that an entity really is the alias it claims to be: That would be tantamount to the "do you believe XXX is satoshi" problem. So the issue of forgery will always be there, so "delegation" in the form I specified must be restricted to specific use cases where all parties are trustworty (e.g. signatures shared with a limited subset of entities like a CoinJoin, not so sure about what else could benefit from this).

Is there something known as delegation problem or you have figured it out as well?  

I appreciate your commitment but if you don't go with a bit slower and lower tempo, it becomes noisy, and eventually spammy, in the worst sense, as you wrap it behind innocent even formal technical stuff, as if there is a real problem, and you are doing your job, as a dev or something, to deal with it, which is absolutely misleading in its entirety, kinda covert spam.

Google it, "delegation problem", to find out that there is just one bitcoin related reference to such thing, and it is Faketoshi backed, nothing more than a scam advertisement!

Interestingly, still their work is more elegant than yours! They propose a same chain of delegation by signing stupid messages recursively, where it is supposed to convince users of a (centralized) entity that they have some authorization on behalf of the original signer.

No matter how anybody would solve or implement it, the sole fact that one is concerned about delegation of authority, puts her out of the bitcoin circle, why? Because, there was actually a delegation problem, i.e, delegation of control over funds; Bitcoin solved it unlike cryptography that had failed it for decades. Resurrecting it, for suggesting an imaginary cryptographic solution, is nothing other than breaking with bitcoin under its umbrella.

Oh, poof! BIP322  

It is crazy. How this delegation is going to be verified and approved anyway? By attaching the previous stupid txn(s) of BIP322 to the current stupid txn? Otherwise, the poor verifier from where should obtain the first one??? Remember, they are not going to the blockchain, so where are they? In Faketoshi Wright's private DB?
Pure nonsense, it is so anti-bitcoin that makes me truly sick.

"Scamming people by presenting it as a bitcoin development with a covert right to double-spend", answered  CSW while blinking  

Proving liquidity to whom? How?
We have nodes pared with each other in channels, each being fully aware of the balance/liquidity available, there is no way for any third party to be aware of this status unless it is running a sophisticated multi-node attack to monitor the fee circulation and other statistics. Publc channels voluntarily advertise their status through gossip protocol, but it is not provable by any means to anybody.

It is also a non problem.
Modern coinjoin services do not rely on liquid providers, thanks to Schnorr blind signatures, CoinJoin is now fully trustless and private, Wasabi Wallet for instance makes it possible for users to join their txns without relying on a liquidity provider middleman.
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Sure, not to mention being useless.

Nice catch. I should probably update the corresponding mailing list entry.


I could've just used OP_RIPEMD160, but I followed the example of P2WPKH-P2SH where the address hash is hashed with SHA256 and RIPEMD160 to create a new, nested address hash, so I prefer to leave it like that.

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There is actually one flaw I found in this scheme - it's that you can't verify that the message is indeed signed with the UTXOs, because they are not even known.

This stems from a tradeoff where you can't have both the privacy of delegation, and verifiability of the delegation, at the same time.

I'm not sure what to do about this.

[I should probably collect all this info on my website instead of dumping it all on the mailing list]

Just use "OP_HASH160 OP_PUSH OP_EQUAL". This OP_VERIFY is needed only if this part should be concatenated with something else as " OP_VERIFY ". Also note that OP_HASH160 is in practice "OP_SHA256 OP_RIPEMD160", so you could use OP_RIPEMD160 instead of OP_HASH160, and then just push 256-bit hash, reached as SHA-256("something").

OK, I just figured out how to solve the delegation problem.

In BIP322, there is a [planned] provision for some person to delegate signing to another person. That means the second person can do all the signing stuff that the first person could do, and the signature is as if the first person signed it.

What this could be useful for?

- L2/Lightning Network, a channel is just 2-of-2 multisig, so a prospective channel co-creator "delegate" signing to the channel itself, by signing a UTXO inside the multisig - signing along with the other party, creating a dummy output (see below), which can be signed to prove liquidity on behalf of the channel, while keeping the channel itself anonymous.
- CoinJoin, To prove that some CoinJoin coordinator is liquid without violating its anonymity by revealing public keys, the person managing the CoinJoins delegates signing from all UTXOs to be used in the CJ, at once, delegating signing to another dummy output.
- By the same token, Mixers can prove their liquidity without revealing their UTXO set.
- Silent Payments, where the public key is not even known in the first place, the address of a silent payment can delegate signing to another dummy output which only the sender and receiver know about.

So how does this delegation work? It's very simple:

1. All UTXOs that want to delegate signing to a different party must sign a preliminary transaction of this format:
- All input/output amounts are zero.
- input 1 is an invalid input of the kind in BIP322
- the rest of the inputs are the UTXOs wanting to delegate signing to a different party, with valid signatures/witness stacks.
- there is only one output, and it is a P2WSH output with the following script:
OP_PUSH OP_SWAP OP_HASH160 OP_EQUALVERIFY
- And the witness stack that will "spend" the transaction in the "to_spend" tx is simply:

- Likewise, the "to_spend" tx has only one input, refering to the txid of the delegating transaction with output point 0 i.e. the UTXO :0. Outputs of "to_spend" remain the same.
-- Contrary to the use of Hash160, we are NOT hashing a public key or script. We are hashing an address hash, implying that we are using addresses.

Do you know why I said "delegating to a different party"? Because it could be a functionally different entity, just like how CEO is diffferent from LLC company even if it has only 1 employee. The "address" here represents a kind of company - it can represent a channel, it can represent a coinjoin, it can represent a silent payment. The channel/CJ/etc. only has to hash the decoded RIPEMD160 of an address, with another SHA256-RIPEMD160, to make an "address" that can be used to sign messages from.

This "address" aka. LLC company can even be encoded with Bech32 to make it look like a real address - obviously don't send any funds directly to that address because they will be lost - and in fact, it *should* be Bech32-encoded when transmitting the Signed Message.

A signed message has these three parts:

Message
Address
Signature

BIP322 specifies the signature is just the raw transaction format of "to_sign". Normally, the address would simply be the address you are signing from, but in the case of delegation, it is desireable for the original addresses to remain anonymous. So since an address must be filled in somewhere, the Bech32 "hash-of-address-hash" created above can be used as a P2WSH address.

Advantages of this scheme:

- The real addresses/UTXOs signing the transaction are only known to each other and whoever is managing the "to_delegate" transaction.
- Only the real signers and the person who is in charge of the P2WSH output can sign the "to_delegate" output and thus sign a message from it (note that they could be the same person).
- There can be an arbitrary number of delegations before the transaction is actually signed (the new person who is in charge of signing, i.e. has the P2WSH output of the "to_delegate" transaction can simply generate another address hash, and delegate to that "address" in another transaction, giving some other person that "address" if they want to)
- Delegated signatures can wrap Full and Full with UTXOs signing formats, so Light clients do not have to directly support those two formats, either for complexity reasons, or because they have no UTXO set.
- And crucially: **There is no on-chain transaction, so the delegation is private and cannot be traced back by the public**.

And there are virtually no disadvantages to this.

I should emphasize that you don't delegate signing to another person, you delegate signing to another party that may just be comprised by one person. I say this because the delegation does not make any new on-chain UTXOs that someone could posess, but it simply creates a hash160 of some address hash that was generated by the delegators, and the hash-of-address-hash does not necessarily have to represent a person, it can also represent a service.

FAQ:

Q: Does this utilize the Full format?
A: Yes.

Q: How to represent the delegation in a signed transaction?
A: Just encode the hash-of-address-hash in Bech32 version 0 and put it in the Address field.

Q: If the delegation is private, then how can the address-hash be known and the transaction signed?
A: The UTXO signers take a random address associated with them and then make the hash160 of that address. Whoever they give this to, can sign a BIP322 transaction.

Q: How can the public verify a delegated BIP322 transaction if the address-hash is private?
A: The hash-of-address-hash is revealed in the Address, not in the Signature. BIP322 states that the signature only contains the "to_sign" transaction, which does not contain the witness stack of "to_spend" that has the hash-of-address-hash (because THAT was already spent in "to_spend") therefore the address hash is Bech32 (version 0) encoded and can be decoded to re-construct "to_spend" transaction and from there "to_sign".

Q: How to differentiate between non-delegated and delegated signatures?
A: You can't. But then again, BIP322 doesn't differentiate between "message signatures from an address" and a signature from a set of UTXOs so it wouldn't be able to identify a delegated transaction anyway.
Rather, a full-blown verification software should present a list-box or a set of radio buttons, that toggles between "Legacy", "Simple", "Full", "Full with UTXOs" and "Full with Delegation" - Each of these controls the content in the Address field - this would already be required to support validating Legacy signatures anyway, which are otherwise incompatible with the transaction-based signing (and this is the workaround BIP322 specifies to support that).

Q: What if the verifier does not have a UTXO set (light clients)?
A: Then present three toggles or radio buttons: "Legacy", "Simple", and "Delegated" - each of these options only require a single encoded address to be specified in the field, and Full, and Full With UTXOs signatures can be wrapped with a delegation to support a single address. Consequentially, these control how the signed transaction is [re]constructed for sign/verify.

Even better: we have OP_PUBKEY and OP_PUBKEYHASH. They make scripts automatically invalid when occured, so they behave as OP_RESERVED, but they are just named. So, "OP_PUBKEY OP_CHECKSIG" and "OP_DUP OP_HASH160 OP_PUBKEYHASH OP_EQUALVERIFY OP_CHECKSIG" could be used to mark transaction as invalid, and turn on backward-compatible verification at the same time.

Exactly. And if we want to make it somehow compatible with "Bitcoin Message", then OP_PUBKEYHASH could represent P2PKH addresses, and OP_PUBKEY could be used to check P2PKs. Then, it can be safely combined with other opcodes, because it would behave exactly as OP_RESERVED, and will mark transaction as invalid when used on-chain, but will be accepted when skipped.

At any rate, it means that besides TODOs, all we have to change in the BIP is specify that "The behavior of OP_CHECKSIG and related opcodes is changed when verifying proofs to hash `to_spend` instead of a real transaction" or words to that effect (apologies if I missed something in this correction).


As far as I know, gmaxwell did not help with the BIP322 design, so why do you keep bringing him up here?

Reading through your post, it looks that there is no template matching, it is verification without interpreter. The fake BIP322 transation is to be verified! A client without the interpreter! People have hell of a job to support it, don't they? Very few are invited to this party, I suppose.

It is not the way you design software, seriously. It is just contingent dependency, we need the message to be signed explicitly, otherwise we are dependent on this verifier.  Now, check a real template based solution and compare the elegance and beauty:
We have three parties: the signer, the verifier and the consumer.

The signer:
 already knows which address should be used, it signs a message with keys for the address, then it attaches the address the script behind it (if any).

The verifier:
First and foremost, checks whether signature is correct per se. If passed, the message is authenticated, but it continues checking if the signer has included supplementary, bitcoin blockchain related info, if so, it compares the address received directly or extracted from the supplied script (template based), comparing it with the keys used, if passed, the address reference is attached to the message.

The consumer module:
Has a signed message with public keys disclosed and a reference to a bitcoin address for profiling purposes and as a metadata.

Such a signed message is independent of bitcoin-like clients/modules, standing on its foot, it is self-contained.

Note that we have a total different scenario here with what Greg Maxwell has proposed:
Here the signed message is the core data, relation with bitcoin is metadata. Greg has put it upside-down because in the real world, we focus on the message. If this up-side down world has an excuse to exist, who am I to oppose, what I'm insisting on is to do it separately and in its own application domain (being a very narrow domain, I suppose).

P.S.
Note how downward compatible and inclusive is the scheme I suggested, with just standard Digital signature libraries, very simple applications can communicate (just ignoring the bitcoin address related meta data) with each other as well as with much more sophisticated applications.

Also note that there is no need to reject the upside-down world, it can exist and do whatever it is  supposed to do.

NO! I think you misunderstand what "template matching" means here. This isn't jamming some other signature format into a BIP 322 signature. There's no "template friendly message" to create, and no signing again.

In this context, template matching occurs against the output script for which the BIP 322 signature signs for. This output script is produced by the address provided, as addresses encode output scripts. A template matching verifier would simply look at the address, see if that address type is one that it understands. Because standard scripts have fixed witness structures, the verifier can look at the scriptSig and witness to see if those match the template, then extract the components that it expects, and verifies that those are correct. This also generalizes to things that don't have addresses, such as Lightning HTLCs, as the script has a fixed structure and so the witnesses will also have a fixed structure.

For example, a template verifier for P2PKH would be given a P2PKH address. It understands P2PKH addresses and knows that it should expect a scriptSig that begins with a byte between 0x07 and 0x49, followed by however many bytes that number was, followed by a byte that is either 0x21 or 0x41, followed by however many bytes that number is. It knows that the first of those is an ECDSA signature, and the second is a public key. It knows that it should check that the public key's hash160 should match the one encoded in the provided address. It knows that the signature, pubkey, and the sighash of the current transaction, should validate using ECDSA. It can do all of this, because the programmer hard coded these things in. If anything doesn't match, it just immediately says the signature is invalid. If it gets an address it doesn't know, it tells the user that verification is inconclusive because it doesn't know that address type.

Template matching is literally just the inverse of signing. It's just that instead of putting things into a scriptSig or witness, it's pulling data out. This technique works for any set of scripts where the opcodes remain in (relatively) fixed positions, the only things that differentiate them are preimages and pubkeys.

Really?  
Just because we have scripts that USE Digital Signature schemes, then we have a Programmable Digital Signature system? Are you kidding or what?
Before rushing to the keyboard, always do your homework: Google it! Programmable Digital Signature System.

Done? As I said, and you quoted, there is no such thing in the world, Right?

As for your show-off with what you've learned about the way interpreter is implemented in bitcoin client:

Please note: We are comparing message signing using templates with this job done using the interpreter, the latter, according to BIP32 is done by putting the message in a virtual/invalid transaction and signing this transaction, these two are incompatible, so, no, they don't reach to an agreement. The only way for this to happen is the ugly dependent way, I briefly described.

For sure, if it holds any water, it would be poisonous, imo.

NO! It will be incompatible with ALL BIP322 generated signatures and vice versa, They belong to two different worlds and only with lots of dependencies and ugly stuff can agree upon a message being signed: you need to generate and sign a template friendly message then put this message in BIP322 virtual txn then again sign it!! lots of other ugly details here.

The question is: why should they communicate ever? One being a conventional message signing algorithm, the other being a special proof-of-authority "thing".

In my view, it is a too long shot which ends in a total miss-fire. There is no reasonable way for circumventing the versioning requirements when you add features, trust me, it will never happen, there is no general solution for all the problems. Soft-forks do not happen in bitcoin on a daily basis, it is not a "project", like what Etherem is, so, it'd be easy to add new templates ever few years or so.

With all due respect, Peter, you need to re-think this approach. You are free to implement your script version and promote it as whatever you wish.
I'm serious, it is useful, but as far as it is not introduced as a signing mechanism, hence "postponing" the development and implementation of a standardized template based (universal) signing system.

The interpreter based system you suggest is good and useful, but in its own domain and universe, for its own (future?) applications.

Wrong. You can always send your coins to " OP_DROP OP_CHECKSIG" and spend them, then it will be quite similar to OP_CHECKDATASIG, the difference will be just in the format of the message: in "Bitcoin Message" you have this famous prefix, here you would have transaction data as your prefix. So, the different message will be signed, but the whole functionality will be the same. Or you could have " OP_CHECKSIG" and use different sighashes that would take your message from the stack instead. There are many options.

Quote

No problem, as super devs you are entitled to do inventions, but as an observer I have all the rights to review and to resist.

Good luck banning "OP_SHA256 OP_EQUALVERIFY OP_CHECKSIG" from the script, and all other variants of that.

Quote

Why should anybody do it?

Because you cannot stop people from implementing it on their own. Having it standardized would mean that their signatures will at least be compatible with some BIP. Now we have a situation, where different wallets implement their own ways of handling signatures, so there is a choice between getting it standardized or not. You cannot stop it, because it is not something that has to go through some kind of soft-fork, it is purely informational no-fork, trying to resist is like trying to stop HD wallets.

Also note that we have almost-BIP-322-compatible network called signet, and note that it can be hijacked to serve the same purpose: the recipient could set some signet challenge, and wait for a valid signed block. The only catch in hijacking the signet is that mining is needed to make a valid signature. But one simple change, and you can get fully working script verifier, if you set the difficulty to the same value as in regtest.

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Then how is it possible to have both, template based and interpreter based implementations in one world?

Guess what, P2SH is template-based and interpreter-based: you have some template, some fixed opcodes here and there, and it works. It is fully compatible with other nodes, because just more data are pushed into the stack, and old nodes simply check if the hash of the script is correct, but upgraded nodes actually execute the script. And here it could be similar: some nodes could know how to handle transactions, and other nodes could simply require some magic bytes in some format, and then perform signature checking on some hashed data, and report everything non-standard as "not implemented".

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First and foremost, stop scrambling the terminology, I know, we all know, Greg is genius, you are genius, ..., no doubts, but we are all humans, sometimes we go too far.

So, go on, and propose some BIP to get rid of the entire Script, and go back to P2PK-only-world. Or make a sidechain for that, and put your coins there. Because as long as we have Script, and as long as it gets more and more complex, there will be use cases for signing different outputs. Unless you want to tell someone that "You have your coins on P2SH/P2WSH/P2TR? Too bad, please move to P2PKH, and sign it, then I will verify it".

It's okay if you don't feel this terminology is warranted. Do you disagree it is useful abstraction?


A template-matching based verifier will only be compatible with a subset of potential BIP322 signatures, reporting "inconclusive" for others. That's the price for not having a full script interpreter.

But even if *all* implementations use just template-matching based verification, this approach still has the advantage of defining a single format that is compatible with *all* potential future extensions that correspond to script features. Because addresses are encodings of scripts, and what we're signing for is the ability to spend outputs sent to a certain address, using script for the message signing too is just the obvious match in my view.


I believe it is entirely uninteresting to work on any kind of message signing system that is restricted to a subset of what script can do. That is postponing another inevitable future problem again, when that subset no longer suffices.

No!
It is just an invention, a bad one: Programmable digital signature. There was no such thing in the world before you guys made it up, right? No problem, as super devs you are entitled to do inventions, but as an observer I have all the rights to review and to resist.

What happened now? Bitcoin script is a digital signature with transactions as their messages, then it evolved to a general pupose one for arbitrary messages? So, there are two consecutive inventions : first we invent programmable DS, and immediately we go all-in to make it even more general purpose? Fantastic but absurd, isn't it?
Or maybe BIP322 is just hijacking (taking) your invention, landing it where it was not supposed to land (through a transposition).  

I understand how it feels, getting high by doing abstractions and generalizations, but it needs to pass some review and criticisn. I'm afraid the vague and loose terminology is a bad sign.

Bitcoin scripting system is not a digital signature scheme, it may use this technology (we have signature free scripts, don't we?). Using a technology doesn't make a system identical with that technology.

However, why should anybody do it? Ruining an established terminology.
What's the catch? Proof-of -ownership or something? Why should it be considered an act of signing? Why don't we simply open a BIP for this one with an appropriate terminology? It is not "message signing" per se, it is "virtual transacting", whatever.

Then how is it possible to have both, template based and interpreter based implementations in one world?
Above thread, I've already discussed it, for now let's check just one issue (there are more, believe me):

For a p2sh where the script is well-formed and can be supported by both, either the message produced by interpreter friendly style is not compatible with template based verification and fails, or it is compatible.
For compatibility, you should
1- Prepare and sign a message template based.
2- Put the signed message in the virtual txn.
3- Supply witness data, using your signature again!
4- Every time check the verifier and supply properly either the virtual txn or the message.

The last step is necessary unless you IMPOSE dependencies on template based wallets.

Ugly & Disgusting.

My Suggestions: (I want to be constructive)

1- First and foremost, stop scrambling the terminology, I know, we all know, Greg is genius, you are genius, ..., no doubts, but we are all humans, sometimes we go too far.

2- Ripping this sign-by-script concept off from BIP322, let it focus on true signing with support for references to standard txns (with well-formed scripts).

3- Make another BIP Just for proof-by-interpretation thing. Find a proper label.

Do not mix signing-with-ref-to-txo and proof-by-interpretation/whatever.
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The Bitcoin script system *is* a (programmable) digital signature scheme on its own, which achow101 is referring to as "script signatures". This digital signature scheme is distinct from the ECDSA/Schnorr signature algorithms available in Bitcoin script (but builds upon it).

• The "public keys" of this digital signature scheme are the scriptPubKeys in transaction outputs.
• The "messages" of this scheme are the spending transactions, excluding witness data.
• The "signatures" of this scheme are the scriptSigs and witnesses in transaction inputs.

It's a programmable signature scheme in that it supports more complex assertions than "a single party with key X agrees"; e.g. it can express agreement of multiple parties (using e.g. a P2SH scriptPubKey with a redeemscript that requires signatures with multiple keys). The actual script semantics are more-or-less irrelevant for this. It just suffices to express the kinds of assertions we care about.

BIP322 is taking this script signature system, and transposing it to a different context: messages that aren't transactions. Everything else remains the same: the scriptPubKeys remain the "public keys" verified against (=addresses), the "signatures" remain scriptSigs/witnesses (but now embedded in a BIP322 signature encoding, rather than being placed in a transaction). However, the "messages" are replaced with a virtual transaction derived from the message being signed, rather than any real transaction. This permits reusing all the script logic a signer and/or verifier may have (however complex or simplistic that may be) for transactions to be immediately applied to messages.

No new opcodes are needed or involved - the only thing that changes is that in BIP322 context, OP_CHECKSIG (and friends) don't compute a sighash from a spending transaction, but from a virtual transaction that is derived from the message being signed. If you want to BIP322-sign for "I have the ability to spend funds sent to address X" with message M, all you need to do is demonstrate your ability to "spend" funds sent to X, using a virtual transaction that commits to M. If you have the capacity (in terms of access to private keys, and in terms of having signing algorithms for it) to do that for the script corresponding to X (whether that's a simple single-key constructor, or something far more complicated) for real transactions, you also have the ability to do that for this BIP322 virtual transaction.

I don't understand any of the concerns brought up here. AFAICT, the only thing necessary to move BIP322 forward is finalizing the last details of the specification, and implementing it (which may mean bring the Bitcoin Core implementation up-to-date, if BIP changes are made, and/or implementations for other software, which may be template based).

I understood the whole script up to OP_CHECKSIG.

From my understanding, OP_CHECKSIG will compute the hash of all the inputs, outputs and script combined together.

For simple and full proof, we can simply compute such signature by hand and place it on the stack for the purposes of equality comparison.

But in the case of legacy proofs, which are supposed to be backward-compatible with the ECDSA (r,s) signatures, it would result in a different signature from when computing r,s from the private key.

This raises an interesting question: P2PKH message signing as it is now won't be removed out of backward compatibility concern, so does the legacy proof simply imply doing the standard ECDSA signing while skipping the entire script interpreter and tx format?

No new opcodes are needed. Just use "OP_DUP OP_HASH160

OP_EQUALVERIFY OP_SWAP OP_SHA256 OP_EQUALVERIFY OP_CHECKSIG", and then check two things:
1) is " " valid for this transaction, according to BIP-322
2) is " " valid for a given "Bitcoin Message"
Then, you can hash "Bitcoin Message" and check the second case in your software, and also consider such signature valid. By making the above script "standard", you can expand verification, just in the same way as P2SH was introduced.

I have addressed some more TODOs in a mailing list post, which I will quote verbatim:


At this point, the core of the BIP is already done, but such cases need to be addressed as "how can I sign a message from the Lightning Network" and "how can I allow another person to sign a message on my behalf, without giving him/her access to my private keys?"

Side note: I don't think most people here even know what a Merkle branch is, the form that is already used in Taproot, so if I prepared an explanation about this data structure, would it help you guys understand what is being proposed here?

Side note 2: I'm starting to suspect that the witness stack which contains the solution to a "challenge" in the second transaction which the spec calls 'to_sign' just has an ecdsa signature and public key (from bottom-to-top order) in the case of P2[W]{SH|PKH} - I'm not really sure what is pushed on a Taproot address, so I may have to make a guide for that too.

[silent transactions as referred to in the mailing list and Github is the same thing as Silent Payments thread started by @witcher_sense].

@NotATether,
It is called "BIP322 discussion thread", isn't it?

Change its title to "I want to join the club by any means", or lock it, whatever, just don't get mad and angry because it doesn't make sense to stop discussing in a discussion thread. 

Guys can we stop with these arguments that aren't accomplishing anything? The point of this thread is to discuss how to solve the edge cases of BIP322 to bring it to final status:


I dropped the old BIP because luke-jr told me it's better to help finalize BIP322, and I want to make change happen [as opposed to whining about it]. That's the end of the story. This thread is not for rambling about why my BIP was (or shouldn't have been) rejected, open a new thread if you want to discuss that.
Message signing with transactions looks ugly but is the only way to demonstrate proof-of-spendability-from-UTXOs. Let's leave it at that.

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Anyway, what I did come here to post was that there is apparently a bunch of TODOs for addressing interoperability with various BIPs and proposals that are likewise in draft or maybe not submitted yet - one of them is interoperability with Silent Payments so this is what I have suggested on the Github issue for it (see the second post of this thread):