Hot answers tagged

9

If you want to avoid all third parties, you need to run a node yourself. Download bitcoin-core and let it sync might take a day or two depending on your machine. You can import your paper wallet by taking the WIF private key and using the importprivkey command in the bitcoin console. Note the rescan will take a while, but once it is done you can spend to any ...


8

No matter which wallet you use, use one with offline transaction functionality. That's what you need. Use Electrum offline: https://electrum.readthedocs.io/en/latest/coldstorage.html?highlight=usb You need two Electrums. You can use the watch-only one on your daily computer, and the air-gapped one on one Tails Linux burned CD. You may instead generate a raw ...


6

It depends on what you're actually asking. Bitcoin doesn't exist within the normal model of BFT consensus so in one sense the answer is mu. Under conventional assumptions Bitcoin will converge on a stable history if honest participants have a majority hashpower. But the arguments given as to why you could expect this hashpower majority assumption to hold ...


6

Is this considered safe enough? Nothing is "safe enough" if we do not know the cost. OK, if you have $100k in bitcoins the 12-words phrase is safe enough. If the 12-words phrase is the seed to the "Method of destroying the Universe" I would recommend to add at least 11 bits of entropy and use 13 words.


5

We don't have federated servers right now but we do utilize open source, publicly accessible libbitcoin nodes which both Airbitz and 3rd parties host. This is a fully compatible replacement to bitcoind nodes but provides much faster blockchain queries, similar to Electrum servers. If you'd like to run one, we'll include it in the list of servers that our ...


4

Safety: Any transaction deemed final by one properly-operating node will eventually be deemed final by every properly-operating node. No two transactions ever deemed final by two properly-operating nodes will ever conflict. Liveness: So long as there is always at least one transaction suitable for inclusion that has not been deemed final by any properly-...


4

There are several ways to store cryptocurrencies, so let's break them down by use-case and safety-level. Exchanges There are, broadly speaking, two types of exchanges. Centralized exchanges, such as Bitfinex, Bittrex, Kucoin, etc., and decentralized exchanges such as Etherdelta and Switcheo. Trading on a centralized exchange requires you to deposit ...


4

Use bitcoin core: https://bitcoincore.org/en/download/ If interested to review and compile yourself, follow the instructions mentioned here: https://jonatack.github.io/articles/how-to-compile-bitcoin-core-and-run-the-tests


4

Your wallet file contains the keys needed to sign transactions that transfer Bitcoins from your accounts. The system doesn't care who accesses what, it just cares that transactions are signed with the appropriate keys. Back up your wallet file so you don't lose the keys you need to spend your Bitcoins. But remember, if someone gets their hands on any ...


4

You can do it manually with highly secure way: Get UTXO's of coins that you want to transfer (TX Hash, Value in Satoshi and No of output). Form the unsigned transaction using outputs from the previous paragraph as inputs to your's new receiving address. Remember that the value of new outputs must be less than summary value of inputs on the estimated fee ...


3

You'd better ask it on the Apple SE, since apparently Bitcoin is not the core of this question, i.e. this could have happened with any software requiring Java. That said, you could simply chose not to use Multibit: switch to another client, be it a desktop client or an online wallet.


3

See https://bitcoil.co.il/Doublespend.pdf. What matters is the number of blocks, not time elapsed or average time for this many blocks. Also, the idea of "wait for 6 confirmations or 1 hour" in Bitcoin is a myth. If 1 hour passes with 3 confirmations you're less secure than if 30 minutes passed with 3 confirmations, because the attacker would have had more ...


3

Nothing. It is mostly only useful for checking data integrity, not detecting malicious modification (unless you know someone trustworthy that signed the hash). SSL has the same problems though, because public keys can be altered too of course. There are multiple solutions to this problem, although none is perfect. Trusting some central authority to decide ...


2

If the blockchain shows the money was in your account, then they have fulfilled their requirements. At that point, any transfer of money OUT of your account needs to be signed by your private key. This signed transaction is what is in the blockchain. The most likely situation is that the application you used to generate the key generated a weak key. If, for ...


2

In short: 12-word seed has enough entropy to be safe against brute force attack. First of all not all 132 bits are random. Seed uses some kind of control sum. Lets talk about 128 bits of entropy. Lets imaging the following attack: We will take one billion (10^9) of the most powerful mining hardware in 2017 (13 TH/s each). We will make a 1000 years brute ...


2

Frankly, I don't think your definitions are useful. But by your definitions, PoS makes a network permissioned by definition. In a proof-of-stake network, you can only participate in the validation of transactions if you possess the token, which you can only get from someone else who has the token and chooses to give it you. By your definitions, that makes ...


2

XPUB refers to an extended public key, and because it is only a public key, you have not compromised your private keys. Thus it is safe to continue using, yes. You have, on the other hand, compromised your privacy, as with that xpub Trezor support can derive all your addresses and know they are all yours. But it's likely they just want to look to see if you ...


1

Safety: never achieving agreement on a state when nodes have not actually agreed on that given state, provided the assumptions of the paper hold (read the wiki here). Liveness: consensus cannot stall, even in case of a tie, algo must always make progress (read the wiki here).


1

Go read Raghav's answer. Here's a shorter answer that amounts to the same but may be more readable if you are in a hurry. Exchanges require me to deposit to trade, is this safe? No, you should minimise the quantity of cryptocurrency you put in their hands minimise the time it is in their hands If I can't trust exchanges They occasionally get ...


1

It is secure in the same way that private keys themselves are secure; the search space is just so massive that the probability of someone generating a private key or seed which someone else is using is extremely small so as to be basically impossible. Nothing protects someone from generating hundreds of thousands of keys and hundreds of thousands of seed ...


1

For the vast majority of possible 12-word combinations, the corresponding wallets were empty and never generated. The total number of the combinations is pretty huge so trying to brute-force them will not work out. In fact, words are just another (mnemonic) way to encode the entropy contained in the private key.


1

If for cash means you want paper then it is possible only theoretically - you sell it in the same way as cucumbers or gas to the people that want to buy it. You just need to find them and it will be hard because if you don't want to do it online means you are afraid of something: fake banknotes, money laundering, etc.


1

128 bits is generally considered more than enough -- 132 bits is certainly sufficient.


1

blocktrail has a 2of3 HD Multisig Wallet API, it's setup like: - the 1st key being your primary key to use - the 2nd key being a backup key you store offline and - the 3rd key being a cosign key owned by blocktrail it only supports bitcoin and bitcoin testnet atm though ... https://www.blocktrail.com/api/docs#payments_overview


1

In my opinion trusting a third party with your Bitcoin savings is kind of against the grain of Bitcoin. It makes perfect sense to keep day to day amounts on hot wallets either on your phone or online by using services such as Coinbase, Blockchain.info, Circle and their likes. These companies offer various cold storage options (e.g. coinbase vault) and there ...


1

Yes. On their sales listing they note specifically that they have passed FCC and CE approval, and their products bear the markings for this accordingly.


1

This is the official guide to building Bitcoin on Linux: https://github.com/bitcoin/bitcoin/blob/master/doc/build-unix.md


1

If you look at the bitcoin protocol specification the calculation of 6 confirmations are considered very unlikely to reverse (even with over 51% of the network hash power) In the case of bitcoin (10 min blocks) 6 confirmations is one hour, with QRK for example (30 sec blocks) its 3 min, if you wait one hour you get to 120 confirmations. To answer the ...


1

There's definitely a certain danger to it. According to this book http://www.totalbitcoinsecurity.com/ there are two easy ways to improve its security: Why put all your money in one paper address? You can split it up and put it in several paper addresses. This makes each address a less attractive target. You can use BIP38 to encrypt the private keys. If ...


1

Look into something like Electrum. It uses a one time password (very long mine is 13 words) to generate all future address in a specific way. This means as long as you have your password, and a copy of the Electrum software it can find all you bitcoins, there is almost no need to "store" them anywhere. You could literally receive bitcoins on computer A and ...


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