No one is immune to theft. Assuming you are is a mistake.

In a perfect world, maybe, but we don't live in a perfect world. Everyone was sure Trezors were perfectly safe, until it was demonstrated that it is possible to extract a seed phrase from a Trezor in under 15 minutes with some fairly basic equipment. The only way to be sure that data can't be extracted is for it not to be there in the first place.

Maybe, but it'll be pretty easy to figure out when my relatives or I find a hardware wallet in my house. Commit it to memory only and the coins are lost forever.

Since you control neither the sending wallet nor the receiving wallet, then you cannot use either RBF nor CPFP. There are no free accelerators other than ViaBTC. Your only remaining option is to privately pay a miner to include your transaction if you are that desperate for a confirmation. You can also do this via ViaBTC, but the cost is usually quite high.

Ledger have this option of permanently attaching a passphrase to a secondary PIN, so you don't have to enter the passphrase each time. When I had a Ledger device, I deliberately did not use this feature for the reasons given above. I don't want my passphrase to be stored on a hardware wallet at all. If it is stored on the hardware wallet, then there always exists the possibility that it can be extracted from the hardware wallet. Yes it's a small inconvenience to enter it every time I need to use the wallet, but I put up with much bigger inconveniences in the name of security.

I also have multiple different passphrases, and so attaching only one of these to a secondary PIN doesn't solve the issue for any of my other passphrased wallets.

All my passphrases are firmly committed to memory, but I still have paper back ups of them all. Doesn't matter how well you have memorized something - a brain injury can make you forget your own name.

I have no idea about Metamask specifically as I have never used it, but each hidden wallet can store any number of different coins. You just need a compatible wallet in order to access each one.

Yes, Electrum supports passphrases. Most good wallets do. You will never run in to a problem of not having software which can recover hidden wallets.

I would also just add that Trezor now support government surveillance and control, and so is a very poor choice of hardware wallet.

If you set a precedent by refunding this, and are expected to refund all future similar scenarios, then either you will go bankrupt or have to break that precedent when someone takes advantage of this and repeatedly claims to still own a funded note which they have actually already spent. Better to not set the precedent at all, I would have thought.

Even if someone can tell you the exact balance on a note, this doesn't solve the situation. I could fund a note of 0.1 BTC, claim I lost the private key, have you refund me that amount, and then contact you again pretending to be a different person and the real owner of that note with a letter of guarantee to prove it.

If you were to go down this route, then rather than disable the other notes why not just wait and see what happens to them? Presumably the owners would notice they are disabled and contact you when they attempted to spend them - either way you will know they are not the note belonging to this user.

In any other wallet or service if you do not save your seed phrase or private keys, then your coins are irretrievably lost. I personally wouldn't expect Whirlwind to be any different.

Although there is obviously no way to guarantee that a user has actually saved the private key or letter of guarantee, perhaps you could not display the deposit address until the download LoG button has at least been clicked?

No. You require both the seed phrase and the passphrase to access the hidden wallet and the coins inside. If you lose the passphrase, then you cannot access the coins in the hidden wallet, even if you still have the seed phrase.

Bad idea. You should back it up on paper, separately to your seed phrase.

If a government is completely blocking the internet in order to suppress and control its population, then I would haven no issues attempting to bypass those restrictions and fight for my freedom, including the financial freedom that bitcoin brings.

Any internet blackout would likely simply prevent access to the outside world, like China or North Korea already do to various degrees. Systems like national banking or emergency response could easily continue to run.

There are alternative options, although they will take a bit of time and effort in order to set up and use.

The easiest way to stay synced with the network without an internet connection is via Blockstream Satellite. It is possible to repurpose any old satellite dish in order to do this.

In order to broadcast a transaction, you need to get it to someone with an internet connection. This might be someone who has bypassed government restrictions, or maybe someone who lives near a border and can use the connection of another country, or someone outside your country altogether. You can get it to them via a mesh network such as goTenna, via SMS, via radio, or any other way you like.

Samourai isn't perfect, but I would readily recommend it over Wasabi. If you do use Samourai, then it's important to enable Tor and link it to your own node to maintain full privacy.

For desktop, then the easiest option is to use Sparrow (also with Tor and your own node) to mix with Samourai's Whirlpool. The best, but more complex, option is to run JoinMarket.

Why would you implement support for a permissioned federation when you have options like Lightning and Monero available to you?

I doubt it very much. There is nothing even close to consensus about this on the mailing list, and even if there was, it would likely take months of discussion on GitHub before a viable pull request was ready to be merged.

Yes. For bitcoind, add the argument -maxmempool=300 where 300 is the number of megabytes you want to set as the upper limit.

Alternatively, you can add the same argument to your bitcoin.conf file.

Bear in mind that Lightning is still very much in its infancy. There are a lot of further developments which are in the works which we will hopefully see come to fruition over the coming years, and there will be plenty of more developments which have not yet been thought of.

Touching on darkv0rt3x's point above regarding opening and closing channels - two developments which are currently ongoing are Eltoo and Channel Factories. In short, these would allow multiple users to cooperate to make a single on chain transaction, and then on top of that single transaction open as many payment channels between each other as they like. This would significantly decrease the on chain footprint of Lightning channels.

Wasabi still offer coinjoins, but they use the blockchain analysis firm Coinfirm to spy on all your inputs and approve whether or not they are allowed to be coinjoined at all. It is the very antithesis of what you want from a privacy wallet, and so Wasabi should be avoided at all costs.

Trezor is simply a gateway to Wasabi coinjoins, so they should also be avoided for the same reasons above.

For a simple desktop wallet which offers coinjoins, then your best bet would be Sparrow (connected to your own node of course), which utilizes Samourai's Whirlpool.

For the best coinjoin implementation, but a more complex set up and use, then go for JoinMarket.

Exactly as it suggests - the number of transactions in your mempool which have not yet been successfully broadcast to any peers.

Although the majority of nodes run with the default setting of 300 MB, there is no requirement for any node to stick to this, and nodes are free to change the memory they dedicate to their mempool.

For the transactions in your mempool, yes. But as we've seen, there are other nodes such as mempool.space which have much larger mempools. As the transaction in your mempool start to get added to blocks and your memory usage drops, your node will start to accept and store these transactions from other nodes with larger mempools.

Bytes is the raw size of these transactions. In OP's example, his 95,792 transactions will fill 65,539,423 bytes of block space when they are mined.

This is different to usage. Usage is specifically RAM usage of these deserialized transactions, not the bytes they will take up on the blockchain. The RAM usage will vary based on everything from his node's hardware to the specifics of the transactions in his mempool.

Size is the number of unconfirmed transactions your node holds in its mempool. Your node is holding 95,792 transaction.

Usage is the amount of memory those unconfirmed transactions are using after they have been deserialized. Your node is using 299,771,632 bytes. By default, the maximum is 300,000,000 bytes (300 MB).

Since you asked about mempool.space, you'll see that under memory usage it currents says something around 910 MB / 300 MB. This is because they have increased their maximum limit from 300 MB to something much higher. If you also increased your node's max memory usage to over 1 GB, then your node would also store the other 200,000 or so transactions which mempool.space's node is storing. As it stands, your node will drop the lowest fee transactions to stay within the default memory limit.

Rather than extract individual private keys as the posters above have suggested, the best thing to do is to recover your wallet via the seed phrase in some software such as Electrum or Ian Coleman, extract the master private key at your chosen derivation path, and then import that using a descriptor to Bitcoin Core in order to recreate the entire wallet.

Blockchair tends to suggest a fairly reasonable fee, so you are fine to keep using it. Generally, however, I suggest using https://mempool.space/ instead, since they give a very nice selection of 4 different fees for no/low/medium/high priority.

If you want to get more advanced, then take a look at https://jochen-hoenicke.de/queue/#BTC%20(default%20mempool),8h,weight, read the text under the graph, and see if you can understand what it is showing you. This lets you then pick a fee yourself and place your transaction exactly where you would like in the mempool, as well as taking in to account things like if the mempool is filling or emptying.

Since my post above not even 24 hours ago, we have now completely caught up with the deficit of blocks and are indeed 1 block ahead of where we should be. We still have over 200 MvB of transactions to process, and at present the difficulty is set to increase at the next retargeting. This should be more than enough to prove to your friend that his hypothesis is incorrect.