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13

You're correct that the offline node needs to how to claim its funds, so it can't be totally isolated. Currently, the most mature offline wallet solution is through a client called Bitcoin Armory. Here's what your workflow looks like with offline wallets: Online node creates transaction -> USB key -> Offline computer signs transaction -> USB key -> ...


11

Electrum is easier. Armory is harder. Electrum lean towards minimalism. Armory is aimed at power users. Even though you asked about offline wallets you will likely want to maintain a watch only version of your wallet on your online system to be able to see the current balance, create unsigned transactions and give out addresses to people who want to send ...


8

It is better to download the actual code from: https://github.com/pointbiz/bitaddress.org (this link is from the bitaddress.org site, no need to trust me :-) Click the "Download ZIP" button. Restart your computer. ** Make sure you do not have an internet connection enabled (WIFI disabled, Ethernet unplugged). Open the zip file. Open Chrome or Firefox. Drag ...


7

It's not Bitcoin Core that's taking up all the space, but the Bitcoin blockchain that Core needs to download, validate, and reference. This is because Bitcoin Core is what's called a full node. There is another type of wallet, called an SPV client, that does not require the full blockchain to operate, but relies on the trustworthiness of other peers in ...


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

You can reduce disk-space usage of Bitcoin-Core by enabling pruning. Enabling pruning means you delete old, already verified blocks without reducing your security. Once old blocks are validated and used for building the UTXO set they are no longer useful for your node. The only purpose to keep them is for sending the blocks to other nodes in IBD (initial ...


5

I'm working on this right now. Currently, I have online and offline armory set up to use the USB key as has been described here before. I just created a new android app that will peer with the bitcoin network, and allow you to scan a QR code representing ANY signed transaction, and broadcast it to the peers. This makes it so you can do this: Make an ...


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 ...


5

You need to be online because mining is sort of like a mathematical race: whoever finds the hash of the next block (with value less than the current target) wins. And in order to prove that you found this value before anybody else, you need to be online in order to broadcast it to other users.


4

Creating a manual offline transaction isn't super difficult, you just need to be careful and think about what you're doing. Make sure you have the public bitcoin address and the private key before continuing. Here's what I do (This assumes you are sending some BTC to one address, some back to yourself as change and some as a transaction fee) Create a ...


4

In order to be able to calculate the nonce for the next block you need all the information from the last known block. The time between the blocks is 10 minutes in average, so if you stay offline for more that 10 minutes you will not be able to perform any valid calculations and essentially you will be in a solo, forking mode, solving the wrong block.


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 ...


3

There are different issues with generating cryptographic keys in general (including private keys for bitcoin) on a downloaded client versus a client served online, as bitaddress.org does. However, I think you yourself should be the judge of what is "more trustable." Here are the issues: Code integrity The problem in both cases is if your client is ...


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

You cannot earn Bitcoins mining unless you either add blocks to the blockchain or cooperate with others to do so. Without being online, you wouldn't know the current head of the blockchain (or any information based on it), so there's no way you could actually do either of those things. You could hash all you want, but you would never mine a block nor ...


3

A1B1: Assuming you've prepared in advance, there are some nice offline wallet options. A1B2: This one's tricky. I'm going to assume that you have access to a computer before running off into the woods, or what have you. I'm also going to assume that you know exactly the amount and address in advance. Generate the transaction and sign it, but don't ...


3

The certificate for www.bitaddress.org is issued by PositiveSSL. Chrome trusts them (PositiveSSL), firefox does not. There are an awful lot of issuers, and different browsers are bound to have slightly different lists. If you trust them or not is up to you. If you trust Chrome's security, then you can trust that certificate. If you "add exception", then ...


3

Currently: yes, you pretty much need an Internet connection. In the future: the relatively-new payment protocol BIP70 can be combined with Bluetooth, near-field communications (NFC), or possibly large QR codes to allow a merchant to send their address to your mobile device and your mobile device to send back a signed payment. Then the merchant will use ...


3

Offline means that the transaction hasn't been sent to the network, that is, it's not in the memory pool of any other node. Unconfirmed means that the transaction has been sent to the network and exists in the memory pools of many other nodes. If the wallet is out-of-sync, that would be the reason it's got 0 confirmations. Even if you did have a ...


3

Here are a list of my best practices for creating a paper wallet. Generate all keys on an offline computer system, this ensures that you are not using an online system that could be sending your keys across the internet. Verify the integrity of the code as well as the integrity of the author, things to check include MD5, SHA1 sums and that author is a ...


3

Solution This works fine. The bitcoins will appear next time I start my wallet application. (Read tuxcanfly answer) Bitcoins are not actually received by the software (wallet) on my computer, they are appended to a public ledger that is shared between all the devices on the Bitcoin network. (Read SPRBRN comment) If someone sent bitcoins when my wallet ...


3

signrawtransactionwithwallet uses the wallet for two purposes: Finding the private keys necessary to sign with (which you dealt with by importing) Finding the transaction outputs that are being spent (without this information you can't construct a valid transaction, and the offline wallet, being offline, does not have access to the transactions that ...


2

Yes this is completely possible. There are services which run fully featured API's that provide almost everything that the client can do. http://blockchain.info/api There are other merchant processors which have similar functionality depending on exactly what you want to do also.


2

Direct answers to your questions: I) Technically this is not too difficult. Looping through every new transaction on each received new block does not take too many resources and checking each transaction against 100,000 public keys is no problem at all. However, I do not know of a tool that would do exactly so. (For example, blockparser can output all the ...


2

"Destroying" the electronic copy is harder than it seems. The right approach is to create a private key offline in a secure way (i.e., with no "electronic copy" beyond volatile ram) and send funds to that address. This can be done with a copy of the html page from BitAddress stored to USB then accessed after booting to a LiveOS, such as an Ubuntu bootable ...


2

The Satoshi bitcoin client has a dumpprivkey command available in the console, which outputs an encoded string of about 50-60 alphanumeric characters. That should be pretty easy to write down, and it can be reimported with the importprivkey command. But if you're really paranoid, why ever have your private key on a computer at all? Flip a coin a bunch of ...


2

You should import the private key using the appropriate feature in whichever software you use. Then you can send the coins wherever you want.


2

If you're paying through your mobile phone, it's most likely that your app creates and signs a transaction based on unspent inputs available to your address. This is then passed on to the receiver who posts it to the blockchain. This transaction cannot be modified, it can only be posted to the network in order to prove payment. So, from your standpoint, ...


2

Electrum lets you manage offline wallets and still safely spend from an online computer. You don't even need to use an insecure USB key, you can use webcams to make the computers talk to each other. See these instructions for more information http://electrum.org/tutorials.html#offline-mpk


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