privacy – How to accept donation correctly?

Imagine a web page that wants to accept Bitcoin donations. A naive approach is to provide a single address on the page and that’s it. The problem here is that the address is known to everyone and if the money ever moves, the address is being reused for new donations after the first spend.

OK, so how can we do better? We can have xpub and generate a new address every time … every time what? The first basic strategy would be to generate a new address as soon as someone sends a donation to the previously generated one. The problem here is that an active monitoring of the web page by a robot simply reveals all the addresses again.

Can we do better? We can, for example, generate a new address per IP address. Doing this, the robot would always see one address that is dedicated to its IP address and unless someone from the robot’s network under the same IP address donated, the robot could not reveal anything useful. The problem here is that if we assume not very high conversion rate, we generate a lot of addresses and most of them never receive any donation. This causes a problem with seed recovery, where there usually is a gap limit defined for the maximum number of empty addresses that are scanned before the scan is terminated. I assume this is quite wallet specific rule, but I assume in general, the problem exists here (does it really?).

So how can we do better? Say we want to use a cold storage using a 24 word seed + passphrase and we are happy to run Bitcoin Core together with the web page. How can we solve donation in a way that is manageable, can be recovered from seed, and at the same time optimizes for privacy? Does a solution already exists somewhere (for example BTCPayServer)? If so, how does it work and what are the privacy properties of such a solution?

context free – Does this grammar accept this words?

It looks the grammar indeed accepts all words of the form $(b+a)^nca^n$ (which means, all words that start with any sequence of $n$ $b$‘s and $a$‘s, and then a single $c$ and afterwards exactly $n$ times the letter $a$).

To show why, try to show the two following things:

  1. every word accepted by the grammar must be with such form

  2. every word with such form has a derivation sequence in the grammar.

The first statement can be easily proved by induction (over sequence derivation length), if you notice that each derivation of $S$ adds only one element to both sides.

The second statement can be much more easily proved, try to think of what derications are necessary to create such words.

accounts – Best way to ask an user to accept the terms and conditions

I’ve currently working on a registration page, and after looking across the internet I’ve seen two different types of way to get an user to agree with the Terms and Conditions.

The first way is to use a checkbox, labelled with “I agree to the Terms and Privacy Policy”

The second way I’ve seen is some text labelled near the continue button, with the “By clicking “Continue”, you agree to the Terms and Privacy Policy” on it. Most technology companies seem to use this option.

Is there any difference between both of them, and if not, which one would be more appealing for the visitors?

air travel – Will the authority accept my second ticket as a confirmation that I am transiting

I booked two ticket from two different companies.

The first ticket is from Germany to Barcelona, arrives in the morning. The second is from Barcelona to non-Eu country departs at night.

Spain currently does not require any tests when going there for a transit. When they ask me for my corona test, will they accept my second ticket as a confirmation that I’m going there for less than 24h without going outside the airport?

domain name system – Network solution does not accept an AWS machine as nameserver

I have set up an AWS EC2 machine as a (BIND) nameserver and I am in the process of making it secondary for several domains we manage. This is cool for all our domain name vendors (e.g. IT-NIC, Marcaria) except Network Solution. I have so far been unable to make their panel to accept the AWS machine as nameserver – the reported reason is that the nameserver “does not exist or is behind a firewall”. The machine itself is already acting as secondary NS for several domains and answering queries regularly.

In an attempt to make NetSol accept the machine I enabled ping, zone transfers and set an MX for the zone the NS is in (which is of course silly, but one never knows). All to no avail, and Google’s not helping.

Has anybody confronted, and hopefully solved, a similar problem?

Advanced thanks.

The only (slighty) unusual thing about the machine is that I do not own the reverse resolution (PTR) for the host – so I am adding it as, but the PTR says the name is

If it serves, the error code returned by netsol’s panel is
“-2313 Invalid host”

❓ASK – Do you think a new business should only accept cash instead of card as well? | Proxies-free

There have been cases in teh past where cards have been declined after the fact and a business faces a problem in then securing the funds from the customer. For a larger business this is manageable as they have the resources to go after the customer and secure the funds or to write off the amount if it is small, however this can be more risky for small businesses as they need the money to progress the business idea and they also do not have resources to follow after a customer. Do you think that it is safer for new businesses to focus solely on cash payments?