First off, only trust highly-reputable software to generate private keys, especially if they're web-based. It seems like this software has only 16 stars on GitHub and only 2 contributors: https://github.com/mikewoods/OfflineAddress.com
To answer your question, the only way to verify that a private key corresponds to the public key is to actually run the ...
Right now, that's not supported. You can try (see user2194702's answer), but if you don't know the exact workings of the wallet, you're very likely to shoot yourself in the foot.
For example, Bitcoin-Qt will send change to a new address every time you create a transaction, and in general does not follow the "balance per address" concept but a "balance per ...
Try using BlockChain.info - you can add a watch only address and then receive email or SMS alerts every time it does anything - so you don't even have to consciously keep an eye on it.
Edit: I apologise, I didn't see that you wanted to use QT for it. I don't know of any way to do this, so propose blockchain as an alternative.
There's really no way for a nontechnical user to know. In fact, most technical users do not have the specific technical knowledge required to evaluate cryptographic code (including the random number generator). Therefore, it comes down to a matter of trust. If the user does not directly trust the software author, they may sufficiently trust somebody else who ...
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 ...
(I assume here that you have a simple single-address paper wallet, like the ones from BitAddress.org. I also seem to have understood that you use the Blockchain.info app to make the payment.)
You should be able to decide yourself where the change goes (using the web-apps's Custom Send feature), but Blockchain.info's default behaviour is to send it back to ...
Most clients will return change to a newly-generated change address, which is not the same as the address on the paper wallet. So if you spend a partial amount, the rest of the coins will go to a change address in your client and the wallet will be empty.
You mentioned using Blockchain.info as your wallet. The Blockchain.info wallet behaves differently ...
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 ...
Go to Blockchain.info
Sign up and after logging in, go to settings. Then in settings, you will see addresses as shown below:
Then click on Import Bitcoin Address as shown:
Then add your private key as it is in the form as shown:
Click import, and you will be able to use your BTC again.
Now to get Bitcoin Cash, just go to Settings > General
There you ...
There is a standard algorithm for generating the keys from the seed words (BIP 39 / BIP 32). Most hardware wallets follow this algorithm (check before you buy). So even if the hardware device has failed or cannot be used, you can still use your written seed words with any other software or hardware device that implements the standard algorithm to ...
My favorite method:
grab out a old/unused pc/mac
install a linux over usb (maybe Talis) (make sure your USB stick is clean!)
download a recent version of bitcoin-core (check hash, verify gitian signatures)
copy bitcoin-core over usb to your offline machine
./bitcoin-cli getnewaddress (gives you a new public key)
./bitcoin-cli dumpprivatekey ...
I'll go through your question clause by clause:
I've made an offline address
You're doing good.
and only have the key stored on 2 encrypted flash drives stored in different locations
As long as only you know the password and the password is sufficiently strong, this is probably secure.
with the private key written physically on paper and stored ...
This wallet design:
1) Has a holiday feel
2) Includes basic instructions on the back for safekeeping and redeeming.
3) Has a number of tamper-evident and idiot-proof features to prevent revelation of private key.
The key to understanding what's going on here is to realize that there are not two, but three components of a bitcoin transaction that determine where coins end up. These are the inputs, the outputs, and the oft forgotten remainder. The inputs to a transaction are the addresses that have coins that are to be spent, and the outputs are the addresses where the ...
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 ...
This is mostly not correct.
First of all, the address is a hash of the public key only.
Also, if one has a private key, the corresponding public key can be computed directly. So the most straightforward brute-force attack looks something like this:
Pick a number to use as a private key (an integer between 0 and 2^256, roughly)
Compute the corresponding ...
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.
You should import all the private keys and not sweep them.
Wallets like blockchain.info has this function where it will import the private key. In that case the private key will become part of the new wallet.
Import all the private keys into a new wallet. Thats it ! During spending the wallet will combine inputs from your private keys to spend required ...
Checking the validity of a private key is a really compute-intensive task to do by yourself, but you can do this without actually using the private key to send coins (so no need to do it using pen and paper).
On the bitaddress.org website the Wallet Details tab lets you enter the private key and after clicking View details your bitcoin address should be ...
Is there global database of all wallet addresses and transactions?
Yes, it is called the blockchain. You can browse it through various websites, called block explorers: e.g. http://blockchain.info, http://blockr.io, http://blockexplorer.com. If you use full node software such as Bitcoin Core, you will download a complete copy of this database (currently ...
You can generate a wallet for cold storage offline easily. You can then ask the exchange to use a public address of that cold storage as the recipient for a transaction. You'd still pay the fee the exchange demands to process the transaction though.
Standard practice is that all trades in the exchange are just bookkeeping and are not published to the ...
1) If you generate your paper wallet on your computer, you have to fully trust your computer
3) If ...
Bitcoin Core will automatically create a new wallet on first start. This wallet will contain 2000 private keys (unless otherwise specified by the -keypool=<n> option) and the seed used to generate those and future keys, at least until you encrypt the wallet.
As such, there is not just one private key that you need to backup, rather you need to backup ...
I found https://github.com/sour-is/bip38tool on github and after a little bit of struggle with the unfamilar golang ecosystem got it installed.
Once installed, the instructions for use are as follows:
./bip38tool decrypt <KEY>
This produces your entire decrypted wallet including the ...
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.
I use Balances.io to track my Bitcoin, Litecoin and Dogecoin balances. You never use a private key. It simply monitors the balance contained in the public addresses. I am not the owner of this website, only a user. I am in a similar situation where I have cold storage wallets and I want to keep track of those balances.
Cointrack.net is a solution for users who need a convenient location to keep track of their various digital currencies stored in a variety of forms.
Cointrack does not store your coin; instead it displays any number of
your address balances. It can also notify you of balance changes
via email. This streamlines the process of keeping tabs on all
of your ...