Re: [bitcoin-dev] Human readable checksum (verification code) to avoid errors on BTC public addresses

From: ts <ts@cronosurf•com>
To: Marek Palatinus <marek@palatinus•cz>,
	Bitcoin Protocol Discussion
	<bitcoin-dev@lists•linuxfoundation.org>
Subject: Re: [bitcoin-dev] Human readable checksum (verification code) to avoid errors on BTC public addresses
Date: Fri, 3 Sep 2021 00:08:42 -0500	[thread overview]
Message-ID: <e81a1400-2b3a-bdeb-ccfd-6aad56c09785@cronosurf.com> (raw)
In-Reply-To: <CAJna-Hhtr0v_uEE-4ET4FPNnGnPv8sW2JXkVka0XDkphy_YmSg@mail.gmail.com>

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Hi Marek,

Marek Palatinus wrote on 8/31/21 3:47 AM:
> I fully agree with sipa and his reasoning that this proposal is not solving any particular 
> problem, but making it actually a bit worse.
Ok, I understand. I'm just trying to find ways to reduce the risk of sending to the wrong 
address and to make the transaction process a bit more user friendly, specially for 
inexperienced users. I am sure that it can be implemented in a way without making it "worse". 
For example, if there is the risk that the user looks ONLY at the code and not at the address, 
then the code should have enough entropy to account for it. If looking at 6 characters is 
considered to be enough, then the code should also be 6 characters long. As I mentioned in my 
following message, the code could be made from specific characters of the address instead of a 
checksum (e.g. first 4 and last 2 characters). By showing these characters to the user 
separately and in a bigger font, he will be encouraged to verify all of these characters.

> Also, do you know what I hate more than copy&pasting bitcoin addresses? Copy pasting zillion 
> random fields for SEPA/wire transfers. And I believe that a single copy pasta of a bitcoin 
> address is a much better user experience after all.

I totally agree with this :)

Cheers,
TS

> Best,
> slush
>
> On Tue, Aug 31, 2021 at 9:08 AM ts via bitcoin-dev <bitcoin-dev@lists•linuxfoundation.org 
> <mailto:bitcoin-dev@lists•linuxfoundation.org>> wrote:
>
>     Pieter, thanks for your comments. Here my thoughts:
>
>     Pieter Wuille wrote on 8/29/21 9:24 AM:
>     > On Saturday, August 28th, 2021 at 5:17 PM, ts via bitcoin-dev
>     <bitcoin-dev@lists•linuxfoundation.org <mailto:bitcoin-dev@lists•linuxfoundation.org>>
>     wrote:
>     >
>     >> Following up on my original proposal, I would like to get some more feedback of the
>     community
>     >>
>     >> to see if this could be realized at some point. Also, any recommendations as to who
>     to contact
>     >>
>     >> to get things rolling?
>     >
>     > I honestly don't understand the point of what you're suggesting.
>
>     It is about creating a simple technical assistance that makes it more user friendly and
>     less
>     error prone to verify the entered address. For all types of users, including those who are
>     less tech savvy.
>
>
>     > * If you're concerned about random typos, this is something already automatically
>     protected against through the checksum (both base58check or bech32/bech32m).
>
>     I agree, but as mentioned in the original proposal, it is not about random typos (although
>     this would help for other coins without integrated checksum of course), but rather about
>     copy&paste errors (both technical or user caused).
>
>
>     > * If you're concerned about accidentally entering the wrong - but honestly created -
>     address, comparing any few characters of the address is just as good as any other. It
>     doesn't even require the presence of a checksum. Looking at the last N characters, or
>     the middle N, or anything except the first few, will do, and is just as good as an
>     "external" checksum added at the end. For randomly-generated addresses (as honest ones
>     are), each of those has exactly as much entropy.
>
>     Correct. However, I believe that ADDITIONALLY to looking at N characters, a quick check
>     of a 3
>     or 4 digit code in bigger font next to the address would make for a better user experience.
>     This gives the user the reassurance that there is definitely no error. I agree that most
>     users
>     with technical background including most of us here will routinely check the first/last N
>     characters. I usually check the first 3 + last 3 characters. But I don't think this is very
>     user friendly. More importantly, I once had the case that two addresses were very
>     similar at
>     precisely those 6 characters, and only a more close and concentrated look made me see the
>     difference. Moreover, some inexperienced users that are not aware of the consequences of
>     entering a wrong address (much worse than entering the wrong bank account in an online bank
>     transfer) might forget to look at the characters altogether.
>
>
>     > * If you're concerned about maliciously constructed addresses, which are designed to
>     look similar in specific places, an attacker can just as easily make the external
>     checksum collide (and having one might even worsen this, as now the attacker can focus
>     on exactly that, rather than needing to focus on every other character).
>
>     Not so concerned about this case, since this is a very special case that can only occur
>     under
>     certain circumstances. But taking this case also into consideration, this is why the user
>     should use the verification code ADDITIONALLY to the normal way of verifying, not
>     instead. If
>     the attacker only focuses on the verification code, he will only be successful with
>     users that
>     ONLY look at this code. But if the attacker intends to be more successful, he now needs to
>     create a valid address that is both similar in specific places AND produces the same
>     verification code, which is way more difficult to achieve.
>
>
>     > Things would be different if you'd suggest a checksum in another medium than text
>     (e.g. a visual/drawing/colorcoding one). But I don't see any added value for an
>     additional text-based checksum when addresses are already text themselves.
>
>     Yes, a visual checksum could also work. Christopher Allen proposed to use LifeHash as an
>     alternative. It would be a matter of balancing the more complex implementation and need of
>     space in the app's layout with the usability and advantages of use. One advantage of the
>     digit
>     verification code is that it can be spoken in a call or written in a message.
>
>     > This is even disregarding the difficulty of getting the ecosystem to adopt such changes.
>
>     No changes are needed, only an agreement or recommendation on which algorithm for the code
>     generation should be used. Once this is done, it is up to the developers of wallets and
>     exchanges to implement this feature as they see fit.
>
>     Greetings,
>     TS
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>

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