Nostr notes by

📅 Original date posted:2021-09-17 📝 Original message:Hi ...

2023-06-07T22:59:34Z

In reply to nevent1q…mrru
_________________________

📅 Original date posted:2021-09-17
📝 Original message:Hi Giacomo,

I wrote the rust implementation of bitcoin signature messages and to
double-check I created some test vectors you can see at
https://github.com/rust-bitcoin/rust-bitcoin/blob/b7f984972ad6cb4942827c2b7c401f590588cdcf/src/util/sighash.rs#L689-L799.
These vectors have been created printing intermediate results from
https://github.com/bitcoin/bitcoin/blob/6401de0133e32a641ed9e78a85b3aa337c75d190/test/functional/feature_taproot.py

Il giorno gio 16 set 2021 alle ore 23:40 Giacomo Caironi via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> ha scritto:

> Hi,
> recently I have worked on a python implementation of bitcoin signature
> messages, and I have found that there was way better documentation about
> Segwit signature message than Taproot.
>
> 1) Segwit signature message got its own BIP, completed with test cases
> regarding only that specific function; Taproot on the other hand has the
> signature message function defined in BIP 341 and the test vectors in a
> different BIP (341). This is confusing. Shouldn't we create a different BIP
> only for Taproot signature message exactly like Segwit?
>
> 2) The test vectors for Taproot have no documentation and, most
> importantly, they are not atomic, in the sense that they do not target a
> specific part of the taproot code but all of it. This may not be a very big
> problem, but for signature verification it is. Because there are hashes
> involved, we can't really debug why a signature message doesn't pass
> validation, either it is valid or it is not. BIP 143 in this case is really
> good, because it provides hash preimages, so it is possible to debug the
> function and see where something went wrong. Because of this, writing the
> Segwit signature hash function took a fraction of the time compared to
> Taproot.
>
> If this idea is accepted I will be more than happy to write the test cases
> for Taproot.
>
> BTW this is the first time I contribute to Bitcoin, let me know if I was
> rude or did something wrong. Moreover english is not my first language, so
> I apologize if I wrote something awful above
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

--
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>;
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📅 Original date posted:2019-11-06 📝 Original message:Hello ...

2023-06-07T18:21:29Z

In reply to nevent1q…9vjj
_________________________

📅 Original date posted:2019-11-06
📝 Original message:Hello Adam,

are you sure you can't tackle the watch-only issue?

What if the proposer create the coinjoin-tx, plus another tx (encrypted
with the shared secret) which is a 1 input-1 output (1to1) tx which spend
his output to another of his key.
At this point when the receiver accept the proposal tx he could create
other tx 1to1 which are spending his tweaked output to pure bip32 derived
key, he than broadcast together the coinjoin tx and for every output of the
coinjoin tx one other tx which is a 1to1 tx.

Notes:
* We are obviously spending more fee because there are more txs involved
but the receiver ends up having only bip32 derived outputs.
* The receiver must create the 1to1 tx or the receiver lose privacy by
being the only one to create 1to1 tx
* a good strategy could be to let the coinjoin tx have a very low fee,
while the 1to1 tx an higher one so there is less risk that only the
coinjoin gets mined
* Whit this spending strategy, the wallet initial scan does not need to be
modified

Il giorno mar 22 ott 2019 alle ore 15:29 AdamISZ via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> ha scritto:

> Just to chime in on these points:
>
> My discussions with ghost43 and ThomasV led me to the same conclusion, at
> least in general, for the whole watch-only issue:
>
> It's necessary that the key tweak (`c` as per draft BIP) be known by
> Proposer (because has to add it to transaction before signing) and Receiver
> (to check ownership), but must not be known by anyone else (else Coinjoin
> function fails), hence it can't be publically derivable in any way but must
> require information secret to the two parties. This can be a pure random
> sent along with the encrypted proposal (the original concept), or based on
> such, or implicit via ECDH (arubi's suggestion, now in the draft, requiring
> each party to access their own secret key). So I reached the same
> conclusion: the classic watch-only use case of monitoring a wallet in real
> time with no privkey access is incompatible with this.
>
> It's worth mentioning a nuance, however: distinguish two requirements: (1)
> to recover from zero information and (2) to monitor in real time as new
> SNICKER transactions arrive.
>
> For (2) it's interesting to observe that the tweak `c` is not a
> money-controlling secret; it's only a privacy-controlling secret. If you
> imagined two wallets, one hot and one cold, with the second tracking the
> first but having a lower security requirement because cold, then the `c`
> values could be sent along from the hot to the cold, as they are created,
> without changing the cold's security model as they are not
> money-controlling private keys. They should still be encrypted of course,
> but that's largely a technical detail, if they were exposed it would only
> break the effect of the coinjoin outputs being indistinguishable.
>
> For (1) the above does not apply; for there, we don't have anyone telling
> us what `c` values to look for, we have to somehow rederive, and to do that
> we need key access, so it reverts to the discussion above about whether it
> might be possible to interact with the cold wallet 'manually' so to speak.
>
> To be clear, I don't think either of the above paragraphs describe things
> that are particularly likely to be implemented, but the hot/cold monitoring
> is at least feasible, if there were enough desire for it.
>
> At the higher level, how important is this? I guess it just depends; there
> are similar problems (not identical, and perhaps more addressable?) in
> Lightning; importing keys is generally non-trivial; one can always sweep
> non-standard keys back into the HD tree, but clearly that is not really a
> solution in general; one can mark out wallets/seeds of this type as
> distinct; not all wallets need to have watch-only (phone wallets? small
> wallets? lower security?) one can prioritise spends of these coins. Etc.
>
> Some more general comments:
>
> Note Elichai's comment on the draft (repeated here for local convenience:
> https://gist.github.com/AdamISZ/2c13fb5819bd469ca318156e2cf25d79#gistcomment-3014924)
> about AES-GCM vs AES-CBC, any thoughts?
>
> I didn't discuss the security of the construction for a Receiver from a
> Proposer who should after all be assumed to be an attacker (except, I
> emphasised that PSBT parsing could be sensitive on this point); I hope it's
> clear to everyone that the construction Q = P + cG is only controllable by
> the owner of the discrete log of P (trivial reduction: if an attacker who
> knows c, can find the private key q of Q, he can derive the private key p
> of P as q - c, thus he is an ECDLP cracker).
>
> Thanks for all the comments so far, it's been very useful.
>
> AdamISZ/waxwing/Adam Gibson
>
> Sent with ProtonMail Secure Email.
>
> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> On Monday, October 21, 2019 4:04 PM, SomberNight via bitcoin-dev <
> bitcoin-dev at lists.linuxfoundation.org> wrote:
>
> > > The SNICKER recovery process is, of course, only required for wallet
> >
> > recovery and not normal wallet use, so I don't think a small amount of
> > round-trip communication between the hot wallet and the cold wallet is
> > too much to ask---especially since anyone using SNICKER with a
> > watching-only wallet must be regularly interacting with their cold
> > wallet anyway to sign the coinjoins.
> >
> > What you described only considers the "initial setup" of a watch-only
> wallet. There are many usecases for watch-only wallets. There doesn't even
> necessarily need to be any offline-signing involved. For example, consider
> a user who has a hot wallet on their laptop with xprv; and wants to watch
> their addresses using an xpub from their mobile. Or consider giving an xpub
> to an accountant. Or giving an xpub to your Electrum Personal Server (which
> is how it works).
> >
> > Note that all these usecases require "on-going" discovery of addresses,
> and so they would break.
> >
> > ghost43
> >
> > (ps: Apologies Dave for the double-email; forgot to cc list originally)
> >
> > bitcoin-dev mailing list
> > bitcoin-dev at lists.linuxfoundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>
>
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

--
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>;
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📅 Original date posted:2019-10-21 📝 Original message:The ...

2023-06-07T18:21:21Z

In reply to nevent1q…2qzh
_________________________

📅 Original date posted:2019-10-21
📝 Original message:The "Receiver" could immediately create a tx that spend the coinjoin
outputs to bip32 keys,
The hard part is that he had to delay the broadcast otherwise he loose
privacy

Il giorno lun 21 ott 2019 alle ore 02:08 David A. Harding via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> ha scritto:

> On Sun, Oct 20, 2019 at 12:29:25AM +0000, SomberNight via bitcoin-dev
> wrote:
> > waxwing, ThomasV, and I recently had a discussion about implementing
> > SNICKER in Electrum; specifically the "Receiver" role.
>
> That'd be awesome!
>
> > As the referenced section [0] explains, the "Receiver" can restore
> > from seed, and assuming he knows he needs to do extra scanning steps
> > (e.g. via a seed version that signals SNICKER support), he can find
> > and regain access to his SNICKER outputs. However, to calculate `c` he
> > needs access to his private keys, as it is the ECDH of one of the
> > Receiver's pubkeys and one of the Proposer's pubkeys.
> >
> > This means the proposed scheme is fundamentally incompatible with
> > watch-only wallets.
> >
> > [0]
> https://gist.github.com/AdamISZ/2c13fb5819bd469ca318156e2cf25d79#Storage_of_Keys
>
> Your logic seems correct for the watching half of the wallet, but I
> think it's ok to consider requiring interaction with the cold wallet.
> Let's look at the recovery procedure from the SNICKER documentation
> that you kindly cited:
>
> 1. Derive all regular addresses normally (doable watch-only for
> wallets using public BIP32 derivation)
>
> 2. Find all transactions spending an output for each of those
> addresses. Determine whether the spend looks like a SNICKER
> coinjoin (e.g. "two equal-[value] outputs"). (doable watch-only)
>
> 3. "For each of those transactions, check, for each of the two equal
> sized outputs, whether one destination address can be regenerated
> from by taking c found in the method described above" (not doable
> watch only; requires private keys)
>
> I'd expect the set of candidate transactions produced in step #2 to be
> pretty small and probably with no false positives for users not
> participating in SNICKER coinjoins or doing lots of payment batching.
> That means, if any SNICKER candidates were found by a watch-only wallet,
> they could be compactly bundled up and the user could be encouraged to
> copy them to the corresponding cold wallet using the same means used for
> PSBTs (e.g. USB drive, QR codes, etc). You wouldn't even need the whole
> transactions, just the BIP32 index of the user's key, the pubkey of the
> suspected proposer, and a checksum of the resultant address.
>
> The cold wallet could then perform step #3 using its private keys and
> return a file/QRcode/whatever to the hot wallet telling it any shared
> secrets it found.
>
> This process may need to be repeated several times if an output created
> by one SNICKER round is spent in a subsequent SNICKER round. This can be
> addressed by simply refusing to participate in chains of SNICKER
> transactions or by refusing to participant in chains of SNICKERs more
> than n long (requring a maximum n rounds of recovery). It could also be
> addressed by the watching-only wallet looking ahead at the block chain a
> bit in order to grab SNICKER-like child and grandchild transactions of
> our SNICKER candidates and sending them also to the cold wallet for
> attempted shared secret recovery.
>
> The SNICKER recovery process is, of course, only required for wallet
> recovery and not normal wallet use, so I don't think a small amount of
> round-trip communication between the hot wallet and the cold wallet is
> too much to ask---especially since anyone using SNICKER with a
> watching-only wallet must be regularly interacting with their cold
> wallet anyway to sign the coinjoins.
>
> -Dave
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

--
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>;
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📅 Original date posted:2018-06-04 📝 Original message:I was ...

2023-06-07T18:12:43Z

In reply to nevent1q…mxdq
_________________________

📅 Original date posted:2018-06-04
📝 Original message:I was wondering why this multi-layer multi-block filter proposal isn't
getting any comment,
is it because not asking all filters is leaking information?

Thanks

Il giorno ven 18 mag 2018 alle ore 08:29 Karl-Johan Alm via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org> ha scritto:

> On Fri, May 18, 2018 at 12:25 AM, Matt Corallo via bitcoin-dev
> <bitcoin-dev at lists.linuxfoundation.org> wrote:
> > In general, I'm concerned about the size of the filters making existing
> > SPV clients less willing to adopt BIP 158 instead of the existing bloom
> > filter garbage and would like to see a further exploration of ways to
> > split out filters to make them less bandwidth intensive. Some further
> > ideas we should probably play with before finalizing moving forward is
> > providing filters for certain script templates, eg being able to only
> > get outputs that are segwit version X or other similar ideas.
>
> There is also the idea of multi-block filters. The idea is that light
> clients would download a pair of filters for blocks X..X+255 and
> X+256..X+511, check if they have any matches and then grab pairs for
> any that matched, e.g. X..X+127 & X+128..X+255 if left matched, and
> iterate down until it ran out of hits-in-a-row or it got down to
> single-block level.
>
> This has an added benefit where you can accept a slightly higher false
> positive rate for bigger ranges, because the probability of a specific
> entry having a false positive in each filter is (empirically speaking)
> independent. I.e. with a FP probability of 1% in the 256 range block
> and a FP probability of 0.1% in the 128 range block would mean the
> probability is actually 0.001%.
>
> Wrote about this here: https://bc-2.jp/bfd-profile.pdf (but the filter
> type is different in my experiments)
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

--
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>;
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📅 Original date posted:2018-05-18 📝 Original ...

2023-06-07T18:12:18Z

In reply to nevent1q…ps2k
_________________________

📅 Original date posted:2018-05-18
📝 Original message:Another parameter which heavily affects filter size is the false positive
rate which is empirically set
<https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki#construction>;
to 2^-20
The BIP recall some go code
<https://github.com/Roasbeef/bips/blob/83b83c78e189be898573e0bfe936dd0c9b99ecb9/gcs_light_client/gentestvectors.go>;
for how the parameter has been selected which I can hardly understand and
run, it's totally my fault but if possible I would really like more details
on the process, like charts and explanations (for example, which is the
number of elements to search for which the filter has been optimized for?)

Instinctively I feel 2^-20 is super low and choosing a lot higher alpha
will shrink the total filter size by gigabytes at the cost of having to
wastefully download just some megabytes of blocks.

2018-05-17 18:36 GMT+02:00 Gregory Maxwell via bitcoin-dev <
bitcoin-dev at lists.linuxfoundation.org>:

> On Thu, May 17, 2018 at 3:25 PM, Matt Corallo via bitcoin-dev
> <bitcoin-dev at lists.linuxfoundation.org> wrote:
> > I believe (1) could be skipped entirely - there is almost no reason why
> > you'd not be able to filter for, eg, the set of output scripts in a
> > transaction you know about
>
> I think this is convincing for the txids themselves.
>
> What about also making input prevouts filter based on the scriptpubkey
> being _spent_? Layering wise in the processing it's a bit ugly, but
> if you validated the block you have the data needed.
>
> This would eliminate the multiple data type mixing entirely.
> _______________________________________________
> bitcoin-dev mailing list
> bitcoin-dev at lists.linuxfoundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
>

--
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>;
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📅 Original date posted:2017-08-28 📝 Original message:Hi ...

2023-06-07T18:05:06Z

In reply to nevent1q…fxef
_________________________

📅 Original date posted:2017-08-28
📝 Original message:Hi everyone,

the Bitcoin headers are probably the most condensed and important piece of
data in the world, their demand is expected to grow.

When sending a stream of continuous block headers, a common case in IBD and
in disconnected clients, I think there is a possible optimization of the
transmitted data:
The headers after the first could avoid transmitting the previous hash
cause the receiver could compute it by double hashing the previous header
(an operation he needs to do anyway to verify PoW).
In a long stream, for example 2016 headers, the savings in bandwidth are
about 32/80 ~= 40%
without compressed headers 2016*80=161280 bytes
with compressed headers 80+2015*48=96800 bytes

What do you think?

In OpenTimestamps calendars we are going to use this compression to give
lite-client a reasonable secure proofs (a full node give higher security
but isn't feasible in all situations, for example for in-browser
verification)
To speed up sync of a new client Electrum starts with the download of a file
<https://headers.electrum.org/blockchain_headers>; ~36MB containing the
first 477637 headers.
For this kind of clients could be useful a common http API with fixed
position chunks to leverage http caching. For example /headers/2016/0
returns the headers from the genesis to the 2015 header included while
/headers/2016/1 gives the headers from the 2016th to the 4031.
Other endpoints could have chunks of 20160 blocks or 201600 such that with
about 10 http requests a client could fast sync the headers

--
Riccardo Casatta - @RCasatta <https://twitter.com/RCasatta>;
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