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14

"Improbable" is an understatement. There are 2256 possible keys. In the entire universe, there are estimated to be "only" 2100 atoms. So the odds of someone else ending up with the exact same address/key as you is far, far less than the same atom, out of the entire universe, being randomly picked twice. If you are worried about an address collision, here ...


9

Basically what Murch said. You have to use the private key to sign the transaction. There is a point I want to add, however. It is possible to send coins without importing the private key into a computer which is connected to the Internet. In fact, this is how a properly run exchange or online wallet service ought to maintain its cold storage. Normally, ...


9

If you are comfortable with a command line, I have used ssss-split and ssss-combine for sharding encryption keys in a n-of-m scheme. These utilities use Shamir's Secret Sharing Scheme to safely break up secrets for later reassembly. For example, you could create a 4-of-7 scheme, where you would hide shards in 7 different locations (personal safe, safety ...


6

Every bitcoin and bitcoin transaction is stored in the blockchain which is online, distributed and known by every full bitcoin node. What you have on your pc are private keys. As long as you have this private key, you can sign any transaction which matches the corresponding public key. An offline, or cold-wallet is a wallet that is not connected to the ...


6

Yes. A paper wallet is basically nothing more than your private key on a piece of paper. For usability it is often represented as a QR code though. You can make copies of it, and store several of them in different places, or even store half of the key in one location and another half in another. Bitcoins are never in your wallet, paper or otherwise; they ...


5

Yes to both questions. You only need a wallet connected to the internet to remove coins from your account, not to add new ones to it. A paper wallet can be used with any bitcoin wallet application.


5

I don't know if this is the recommended way, but I did this by using the Send Nxt API call on an offline computer, storing the transaction bytes, and broadcasting the transaction from an online computer by using the Broadcast Transaction API call.


5

The system you describe is similar to the way Armory suggests you use it. You can sign a transaction offline, then transfer that signature to an online computer and broadcast it. Your private key has never been on an internet-connected computer, but your transaction has. That said, be very careful spending from a cold storage address. There are many ...


4

Bitcoin Armoury is the best thing out there for this. What you want to do is create a new wallet with armoury, create a receiving address and send your BTC there. The best thing is you do not need to even be connected to the network, synchronized or anything. Armoury can run offline in the dungeons far underneath the earth (like your cellar :) ) You then ...


4

I believe the basis of this recommendation is clients' tendency to create invisible change addresses. A transaction sending the entire balance to a known address eliminates the possibility that a part of the balance could be lost when a private key for a change address is not retained.


4

I tested it by creating a secure wallet on BitGo. They gave a multisig address for deposits. 2/3 of keys are needed to withdraw Bitcoins. BitGo holds one key, you get private key and backup key. You don't need to printed private key to withdraw Bitcoins. the passphrase is enough (apparently the key is derived form the passphrase). BitGo cannot do Bitcoin ...


4

BIP38 wallets are significantly more secure and are resistant to brute-force attacks when a decent passphrase is used. Generally the term "Brain Wallet" refers to one in which the private key is derived from a phrase you make up. These have been shown to be insecure because humans are bad at entropy and generally anything easy enough to remember is not ...


4

Here it is step-by-step Run armory in offline mode (simply run armory --offline) Import the wallet into armory if you haven't already. (Import wallet, etc) (you probably don't need to do this if you have it on USB, just run that instance) Click on the wallet and click "Backup This Wallet" and enter the password. Select "Export Key Lists" and click the ...


4

You can just do it yourself instead of having to send a 3rd party your private keys. Here's one that I wrote using nodejs and bitcore-lib that takes a WIF and sends all funds to a different address. https://github.com/coinables/sweepkey/blob/master/app.js


4

The precautions you can take from an architerual point of view would be as follows: The database storing the private keys or the seeds in case of HD wallets should be running on a separate instance and only accessible via the application server(AWS allows lots of configuration you can make in the virtual private cloud i.e. VPC to accomplish this). The keys ...


4

While theoretically possible, the algorithms involved mean that it is practically impossible. You would need to compute the seed from your mnemonic word according to BIP 39, and then derive the keys and address from that according to BIP 32. Generating the seed from the mnemonic alone requires executing the PBKDF2 function, which is specifically designed to ...


4

Q1: Depens on how you use it. Transactions to an address does not decrease it's security. Using a cold-storage wallet and taking it online exposes your wallet and it's security. Q2: It's correct. Most exchanges require KYC(know your customer), they store information about you and your withdrawal addresses. It's possible to create a new address for each ...


4

Fees are not based on the value that is being transferred but rather the size of the transaction in bytes. The fee is to pay the cost of storing the data that makes up the transaction itself, not for the amount that is being transacted. Thus giving the fee as a percentage of a value will be completely inaccurate and giving a fee estimate for the cost of ...


4

The generation of private keys is made randomly. Therefore, it is possible for someone to generate the same private key as you did. In your question, you heavily insisted that you did not want an answer on how improbable this is. The answer is : You cannot protect your paper wallet from someone having incredible chance and getting the same number generated ...


4

Use TAILS Linux. From the website: Tails is a live operating system that you can start on almost any computer from a USB stick or a DVD. It aims at preserving your privacy and anonymity, and helps you to: use the Internet anonymously and circumvent censorship; all connections to the Internet are forced to go through the Tor network; leave ...


3

I wouldn't recommend CD/DVD or USB sticks. CD/DVDs don't actually have that long of a lifespan. Googling around I found various different estimates and no exact number, but the consensus is that they will probably last less than 10 years. Finding an estimate for how long a usb drive will last is a little bit more hazy, but the numbers I saw for that were ...


3

I would personally use a linux/bsd computer, without a desktop-environment. This means, you'd command a bitcoin command-line client without having a graphical interface. Probably something like FreeBSD or Ubuntu. This computer can still be online and used for everyday transactions, but it's much less prone to keylogger attacks and any other sort of attacks ...


3

It depends! The problem is that almost all PCs are relatively unsafe. As Bitcoin use becomes more widespread and Bitcoins more valuable, we'll probably soon see more malware looking for it. Naturally, if you limit your internet usage, you are less exploitable. Yet only one such malware need to make it onto your computer, and then connecting even once to the ...


3

I have successfully used Electrum wallet with cold storage. I found this one of the most novice friendly options, though getting money out from the cold storage is still quite a complex task. Specifically, here is a tutorial how to create a two wallet: online and offline. Then you can transfer bitcoins from online wallet to offline wallet. http://docs....


3

Since version 0.10.0 bitcoind has support for watch-only addresses. Here is the text from the release notes: Watch-only wallet support The wallet can now track transactions to and from wallets for which you know all addresses (or scripts), even without the private keys. This can be used to track payments without needing the private keys ...


3

Bitcoin-qt only asks for your password when you do an operation that requires it, such as sending coins. Currently, wallet.dat must be called that and reside in the Bitcoin data directory. It might be possible to use symlinks to work around that.


3

Since you need the private key in order to sign the transaction, you cannot send a transaction without touching your private key at some point. However, you could use a thin client such as MultiBit instead of Bitcoin-Qt in order to get around syncing the full blockchain.


3

It sounds like a lot of hassle to send bitcoins because you have to re-install you offline armory each time. Also, the fact you're trying to do it on a live CD tells me you likely don't have an air-gapped machine. If you think your wallet won't "touch the Internet" in such a case, think root-kit. I would advise against this. Instead, get a cheap Raspberry ...


3

The standard client doesn't have any built-in options for this. You could manage it yourself if you built the transaction by the RPC API commands or, more easily, by using a client with that feature built in, like Armory: Or, if you know what inputs will be used and the exact amounts involved, you can add the "change" yourself as an additional output. This ...


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