By creating a wallet using the master public key, the new wallet will effectively become a watch-only wallet. This means that the funds can't be spent from the new wallet and you have to spend it from the wallet that you've gotten your master public key from.

Could you go to your desktop wallet and go to the console tab and type this, with the field inside replaced with the address you've sent to:

If the argument returns false, your desktop wallet doesn't have the address and you can't spend the funds.

Shapeshift.io is pretty safe [1] and they have been around for a long time. You can purchase Ledger using BTC from their official store.



[1] https://bitcointalk.org/index.php?topic=717973.0

It's possible for bugs to exist everywhere. However, for a product like Ledger, security should be their top priority. With the recent case, a researcher has disclosed the vulnerability to them responsibly. The vulnerability is serious in the sense that the device could be compromised and tampered if any entity wants to do it or if the seller wants to. They dismissed the claim and gave everyone a false impression that a device that has been proven to be insecure is still secure.

Considering its price, I would say the main attractiveness is how cool the concept is. If you put it securely and someone who knows that you own Bitcoin is trying to rob you, they would probably be finding a paper with words on it rather than a paper that looks like an useless printed piece of paper.
You can use the same secret key for all of them. You aren't supposed to put all of them together. However, you do need to use the corresponding PVC sheet with the noise on the corresponding printed

Unless you have the sole ownership of your private keys and the choice to follow whichever version of the web client you want to use, an online wallet is just about as safe as a shared wallet. Recommending blockchain.info to anyone is just outright a terrible opinion. Their security is notorious for being compromised all the time and they are incompetent in running a wallet or a block explorer.

That's in the perfect scenario. Electrum does not verify all of the blocks fully as with all SPV clients so you have to trust the server that you're connected to to check the validity of the blocks to the network rules. Bitcoin Core does also have the same feature as Bitcoin Core, just with the lack of UI. If you can follow instructions, Bitcoin Core can do the same as Electrum, arguably more.

Master Public Key is definitely pretty safe to give out. The only thing that you could potentially lose is privacy since everyone can essentially know how much you own and which transaction belongs to you.

Without the child key, you can't do anything with the master public key that could give you your master private key. The theory is stated here: https://bitcointalk.org/index.php?topic=657205.msg7385160#msg7385160 and the derivation is in this BIP: https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki#Child_key_derivation_CKD_functions.

That's correct. Nonce are pretty limited since they are only essentially numbers that has a max limit of 4 bytes.

However, I suspect that it won't be the first data that they would change when the nonce is exhausted. The block header consists of merkle root, hash of last block, target, time stamp, version and nonce. Of them, the merkle root, timestamp and nonce are pretty variable. The miner would likely change the timestamp and the nonce first before trying to change the merkle root. The miners aren't fond of changing the merkle root first as it takes additional computing power.

Changing the merkle root doesn't mean that they will include/exclude any transactions. The miner can simply change the order of the transactions or extra nonce to change the witness commitment and the merkle root.

Not possible. The addresses are generated from the master private key but it probably can't be reversed using only the private key. However, the implementation of BIP32 could indeed allow someone to calculate the master private key using both the master public key and the private key. This would only be applicable for unhardened key derivations, ie. those with master public key AND master private key.

It's an irrelevant argument since the privacy would be compromised anyways if the master public key is leaked. You've got bigger problems to worry when someone has both your child private key and master public key.

It's a wallet. Addresses are generated and transactions are signed on Trezor. The only thing that gets transferred out should be your signed transactions. The reason why it has to be connected to another device that is connected to the internet is because Trezor has to get the information on the UTXO of your addresses using the internet.

Yes. You can purchase Ledger using BTC. I would be wary with Ledger given their reluctance to admit that the security vulnerability was potentially quite serious.

Go to File>Receiving Address. This will display all of the addresses that were generated by you to receive payments.

If you want to get every addresses in the wallet, go to Help>Debug Console>Console and type:
.

Mnemonic seeds are first converted to the master private key (seed) before being generated to a private key. Each private key can be generated from one and only one master private key since HMAC-SHA512 is applied to the master private before being generated and unless a collision is found, the hash will not be the same.

Mnemonic phrase will always decode to the same master private key and subsequently the same private key.
Yes, according to BIP39 standards. You can select the words from the wordlist yourself and you can generate a seed from using any mnemorics. However, depending on your client, you might need to have the correct checksum.

Bitcoin cannot be known as a global currency as of yet. Even if Bitcoin does indeed grow exponentially, it is not indicative of its status as a currency. Many countries still do not recognise Bitcoin as a legal tender and it is unfair to call something a global currency if it can't be used anywhere. The adoption rate is way too low.

Even if Amazon accepts it, that would just be a single corporations and it doesn't mean everyone would use it.

No. During the mining process, the miner assembles a set of transactions and other data to be put into the block header. Using SHA256, the block header is hashed twice and if and only if the hash meets the target, the miner will broadcast the block to the network.

The miner will not broadcast the block if there is a block there has been broadcasted before his at the same height. If he does, every node in the network will simply reject it as there is a chain with a longer proof of work. The miner can only be rewarded if his block is valid and is recognised as such by the network. There is simply no reason for anyone to broadcast a block that is below the current block height if they won't get rewarded for it.
No. While the miners are technically competing against each other, they are still somewhat working together to build the chain. If the miner has less than majority of the hashrate, it is not profitable for him to have a competing chain to the rest of the network since he will lose with the others holding more hashrate than him and thus possibly having a longer chain.

Do not use Electrum 2.7.9. It has a vulnerability that would potentially result in your wallet being compromised.

Go to https://electrum.org/#download and choose your version (verify it if you want to be safe). Update it, run it. If it still doesn't connect, click the bubble at the bottom right, go to server tab and uncheck connect to server automatically. Right click to choose another server and close it.

Were you the one that sent the transaction? From what I can tell, the block explorer didn't make any mistake. The address you're seeing is a bech32 address (bc1 prefix) and it is a standard for native segwit address and it's perfectly valid. The only reason why you can't parse the address on various block explorers is because they don't support it yet. Blockchair.com does support bech32 address.

To my knowledge, no block explorer actually displays the public keys involved. They can be derived from the redeem script.

No. The whole motivation for Bitcoin to exist is to free it from the government and any other factors that could affect the currency. If its decentralised, there shouldn't be any mechanism built-in such that the users cannot choose who should be the intermediary.

You can't attempt to change Bitcoin's very fundamental values. If you do, you're creating an altcoin. You can get an intermediary with a trusted party and multi-sig but that's pretty much it.

Electrum will always attempt to open the file named default wallet in the data directory. Have you written down the 12 word seed?

If so, assuming you're using Windows, you can go to %appdata%/Electrum in your file explorer. Move the default_wallet file away from that folder into another location on your computer. Restart Electrum and the client will prompt you to either restore or create a wallet. Select  Standard Wallet> I already have a seed and the rest is pretty self-explanatory.

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Anyways, are you sure you have never encrypted it? It sounds pretty weird if you hadn't done so. Someone else must have access to your computer, check your computer for malware and check if anyone has used your computer.

If hardware wallets fails simultaneously, only the people who has not backed up their seeds would suffer. Those who has done it is perfectly fine. Hardware wallets uses the same standards as some of the desktop wallets that you've seen around. If they fail, then all of those desktop wallets would fail too and that is probably not going to happen.

If you're talking about it in the security aspect, then yeah of course they could fail. You can't trust the people who has designed the hardware wallets to not include any backdoors but their reputation is pretty important to them. If they aren't safe, no one can do anything after the attack. If you don't trust them, you can audit the code yourself. If you don't, you aren't safe; even with desktop wallets the trust is with the developers.

You can. Armory basically uses Bitcoin Core as a server to obtain all the information and they build their database based on it. Armory can only work when bitcoind is present and running at the specified directory. You can certainly be running Bitcoin Core and Armory at separate times since Armory won't make any changes that makes it incompatible.

However, since Armory starts bitcoind at start up, you have to disable that if you want to run Bitcoin Core and Armory simultaneously. You can run bitcoin-qt first then Armory after you've done that.

You would need a Ledger Nano S to actually use anything related to it; installing anything won't turn your computer into a hardware wallet. Where did you get the software? While your computer scan might not have any malware infections, some malwares are undetectable.

What were you given when you got the Bitcoins? You can't get Bitcoins without actually getting a file or a string of alphanumeric letters.