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Electrum has that function; but it's more of a "coin-control" feature than safety.
Because it's possible client side - freeze an address or UTXO from being spent (though that client) but it wont stop anyone who already got your private keys from spending your coins.
It won't? That's terrible! Well that's not going to work!
You can freeze your outputs with specific time parameters, so that the outputs in that specific address can't be spent until the time has elapsed.
I know but the problem is, when I need to use my money I need to use it. I can't really afford to always wait for days or weeks for something to get unlocked. I might be able to wait for hours or a couple days at most but then once I use what I need, I need to be able to freeze my address again until the next time comes around. The truth is though sometimes I might even need to use my money on the spur of the moment without any waiting at all!
I don't think a nTimeLock parameter would help the OP, at least not alone. From what I can tell, the OP wants the ability to "freeze" his coin as a security measure. If the OP's private keys are stolen, the attacker could simply wait for the time lock to expire. Also, the OP would be unable to spend his coin at an arbitrary time.
On point. The part about spending my money at an "arbitrary time" thanks for bringing that up too.
The "freeze" feature as described by the OP is really more of a loss prevention measure for the bank as the bank is the one who will be on the hook if there is an unauthorized transaction.
Well I don't know about that but what I do know is it give me an incredible peace of mind knowing that because I clicked the freeze button, there is no transactions being done with my card. But the moment I need to, I can just click on unfreeze and do my business and then freeze it again, making it impervious to the outside world even if they know my card number and such. that's security, I tell you!
Now there is that matter of what would happen if I lost my credit card and someone else found it and I didn't even know about it. Well, I'll be happy to explain what would happen in that case too. You see, they wouldn't be able to use it even though they had it in their physical possession. Even with the 4 digit code number on the back of the card it would do them no good. Because when they tried to go to an atm machine or buy something, it would get declined period the end. And when I got around to noticing that someone had stolen my card, I could just call the bank and get a new one sent out, credit line transfers over to the new card. You can't beat that! I'm sure bitcoin will get to that level at some point. which will be cool. maybe that's part of taproot, not sure! there's alot of taproot experts out there, and i wouldn't put it past them to understand how that could work with this.
A 2 of 2 multisig doesn't "freeze" anything, you will need both keys at all times to be able to spend coins from the created address. Additionally "freezing" usually requires a time component where user locks up their coins for a certain period of time which is not possible with multisig.
You see I was thinking of making my friend an authorized cardholder but I told them you can't just spend money without my approval. They said they would always ask me before they tried to do any transactions. So I ordered them a credit card with their name on it the funny thing is it had my account number on it! Same credit card number as my credit card. I guess theyre really serious about me being on the hook for anything my friend would spend with their card. What I figured out though is, I would probably have the ability to "freeze" their card and keep it in that state until they came to me and asked for permission to use it and then I woud unfreeze it so they could buy what we agreed on but the thing is, how do I know how much they are going to spend? That's the real problem. I'm on the hook for whatever they decide to spend when its in the unfrozen state. After a bit of thinking about it, I came to the realization that it would simply be easier for me to just keep my credit card to myself and if I want to buy them something I can do it that way.
You can have signed transaction that will allow for example to send coins only to selected address. You can make some such transactions upfront, sign it with your "freeze key" and then pick one of them, sign it with your "real key" and broadcast. Also, multisig can be combined with locktime if needed.
That's the problem with my credit card company though. When my card is in the frozen state, I can't even create transactions that a vendor would broadcast at a later time. Can you imagine that? They wouldn't even just take down my card information and give me 30 minutes to get home to my ultrasecure desktop airgapped computer to unfreeze my credit card. How dare they?
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Additionally "freezing" usually requires a time component
There is some weird and inefficient way to "freeze" coins without any timelock, for example someone can start with some public key, add some nonce, and increment it until hitting some target. Then, it is possible for example to store that key in some safe place, but store only the starting point in the wallet. In this way, it is possible to unlock the key after redoing all computations, which takes time, so it is guaranteed that for example you need 2^48 operations to recover your key.
There is some weird and inefficient way to "freeze" coins without any timelock, for example someone can start with some public key, add some nonce, and increment it until hitting some target. Then, it is possible for example to store that key in some safe place, but store only the starting point in the wallet. In this way, it is possible to unlock the key after redoing all computations, which takes time, so it is guaranteed that for example you need 2^48 operations to recover your key.
Yeah I tried that method with my credit card actually and it didn't work here's what happened. I put my credit card in a glass bottle and buried it in my garden. That way no one could ever use it, except me, right? Problem is someone somehow got ahold of my credit card number and used it to subscribe to some porn website. The credit card company was familiar with the porn website and contacted them to see if it was really me. Turns out, they don't know who it was but they can't prove it was me so I got my money back. But I sure am glad that my credit card company implemented this "freeze" feature because now I don't have to go digging it up in the garden everytime I want to use it.
Oh and I finally found out how someone got ahold of my card number too, they were just rummaging through some trash and found an old credit card statement it wasn't even the statement for my credit card though can you believe that? But the account numbers were close and they made a mistake typing in the card number off the trash they found and that typo ended up being bad news for me but as I said, the credit card company made me whole again. So it's all good.
[moderator's note: consecutive posts merged]
