Brainwallet bitcoin wikipedia

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Security is especially important in Bitcoin because if your BTC is stolen, there is often no recourse. Bitcoin transactions cannot be reversed. There are two very different use-cases for passwords in Bitcoin. The first and more common is brainwallet bitcoin wikipedia "offline passphrase".

With an offline passphrase, something prevents an attacker from trying to guess your passphrase as fast as he might like. All of the advice you've ever heard about password security has been for the offline password use-case. The second use-case is an "online passphrase", where the passphrase is essentially the only thing protecting your BTC.

In this case, your passphrase much be massively more secure than usual, and you can not rely on any password-creation advice you've ever heard. For use cases that are vulnerable to a global passphrase cracking search, imagine that the entire world could be constantly trying to crack your passphrase, billions of attempts per second, all the time and with no restriction.

This is not a normal situation outside of Bitcoin. Between 64 and 80 bits of entropy seems reasonable. The password must be totally random see later sections on generation. Usually you don't have to personally generate an online passphrase. The most common case of an online passphrase in Bitcoin is the mnemonic for an HD wallet seed, but a good wallet should securely generate it for you this is the several-word mnemonic that most wallets tell you to write down when first runassuming it has not been tampered with.

In case you need to manually generate an online passphrase, bits of entropy is required. The passphrase must be totally random see later sections on generation.

For high risk applications, a pair of fair dice can provide a simpler, verifiably secure source of entropy. Humans are really, really bad at generating passphrases on their own. If at any step in the passphrase-generation process your brain is being used to choose something at random or randomize something, then you're doing it wrong. Dice can be used as one way to generate random numbers and passwords. However, in order to achieve security, you must use them in a certain way.

Casual dice for board games are not shaped perfectly, and will be somewhat biased toward certain numbers. Special casino dice are available which do not have this flaw. The extent to which slightly-biased dice actually affect real-world security depends on the use-case.

For the use-cases on this page, if the dice is random enough to not notice its bias when playing games, then it is probably good enough. To generate passwords, write down a brainwallet bitcoin wikipedia of brainwallet bitcoin wikipedia characters, and sequentially number each character starting from 1.

For example, if you want to generate a 4-digit PIN, you would create a list like this:. If you wanted to generate a password with characters in [a-zA-Z], you would create a list like brainwallet bitcoin wikipedia. Now you need to figure out how many dice you're going to need brainwallet bitcoin wikipedia roll. Your dice should all have the same number of sides.

If your character list brainwallet bitcoin wikipedia C characters, and each of your dice have S sides, then you need to roll log S C dice, rounded up. For example, log 6 52 is about 2. So if your character list contains 52 characters, then you need to roll 3 6-sided dice. Here, the dice are brainwallet bitcoin wikipedia to brainwallet bitcoin wikipedia numbered from 1 to S.

If this is not the case, then you must create a system to translate the dice results into a range from 1 to S. For example, if you are dealing with sided dice labeled from 0 to 9, then you can add 1 to the roll.

Brainwallet bitcoin wikipedia the required number of dice and put them in a random order. Do not sort the dice from highest to lowest or anything like that. In fact, to prevent any personal bias from entering into the ordering, you may want to roll the dice and then put the dice into a line with your eyes closed.

Say that d 0 is the rightmost dice you rolled, d 1 is the second-from-rightmost dice you rolled, etc. Then the random number is:. If your number is larger than you need, then you must totally reroll for this character. Do not try to "wrap the numbers around" or keep only certain dice, as this results in a non-random distribution.

For the adventurous only: You can safely reduce the number of rerolls by pretending that the highest-order die has fewer sides. Still multiply it by the appropriate power brainwallet bitcoin wikipedia 6, not 3 or 2. But the die must be evenly divided, you must ensure that the maximum possible value is still greater than or equal to the highest-value character, and you must use the exact same treatment of the high-order die throughout the generation process.

There are a variety of different brainwallet bitcoin wikipedia to get a random number from multiple dice, but they brainwallet bitcoin wikipedia usually non-random.

For example, adding dice would be very non-random. The above method ensures a random distribution if the dice themselves are random and if they are ordered randomly.

If the password is L characters long, then password has log 2 C L bits of entropy. Note that there is a risk when acquiring your wordlist of an attacker giving you a wordlist that has duplicated or brainwallet bitcoin wikipedia similar words. For example, the wordlist might look like brainwallet bitcoin wikipedia contains 1 million words, but actually be the same words repeated over and over again.

Or all of the words might have an "o" in the fourth position. This can cause you to significantly overestimate brainwallet bitcoin wikipedia security of your passphrase. Therefore, you must acquire your wordlist from a trusted source.

First, decide how many bits of security you want. We will call this value B. Next, roll log S 2 B dice, rounded up, where S is the number of sides per die. For example, with 6-sided dice you would brainwallet bitcoin wikipedia to roll 50 dice. Put the results right next to each other in a string of text, so for example if you roll 3, 2, 5, 6, 1, you'd start your string as "", and then continue on for a total of 50 digits. If your dice have enough sides to result in two-digit numbers, put a leading zero in front of single-digit numbers.

Then hash your string with a command like echo " The resulting hash is your random number. If you want a bit or bit number use shasum or shasum, respectively. If you want some in-between number of bits, use the next larger hash size and then cut off the number where you need it.

You can generate any size of random number by combining the outputs. For example, let's say that you want bits of brainwallet bitcoin wikipedia and for some reason you can only use shasum.

You can do this like:. Then concatenate all of those hashes to get your final random number. In brainwallet bitcoin wikipedia example the result is cf6a25b When generating a stream of random numbers like this, you have to put your source entropy back in at each step. If you want to generate a number in a range with a range size that is not a power of two, choose the next-largest power of two and select the correct number of bits based on that.

If the resulting number is too large, discard all of those bits and grab new ones from the endless stream of random bits. Do not use the modulo operator, as that introduces a bias. If your random stream starts 0xA52F This is in the range, so the final result is 5. When generating raw Bitcoin private keys: When generating a Bitcoin private key, you should check that these conditions are met; if not, reroll the private key.

Some software might allow you to use these invalid private keys, but doing so would be insecure. Computers are good at generating secure random numbers, but you have to be careful to use the right commands. A lot of commands, programming language features, and snippets that you'll find online will give insecure brainwallet bitcoin wikipedia numbers which look random, but are predictable. Do not get your passwords from brainwallet bitcoin wikipedia in a Web browser, even if the page says that it's using purely client-side JavaScript.

If you would like a more concise and easy-to-use command, we recommend installing an actual password generator package. Note that this command will never use brainwallet bitcoin wikipedia outside of ASCII, even if your grep pattern would select such characters. To generate a passphrase made of words, create a file called words with one word per line and Unix-style line endings, and run:. KeePass includes a password generator, though not a word-based passphrase generator.

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A cryptocurrency wallet stores the public and private keys which can be used to receive or spend the cryptocurrency. A wallet can contain multiple public and private key pairs. In case of bitcoin and cryptocurrencies derived from it, the cryptocurrency is decentrally stored and maintained in a publicly available ledger.

With the private key, it is possible to write in the public ledger, effectively spending the associated cryptocurrency. When choosing a wallet, the owner must keep in mind who is supposed to have access to a copy of the private keys and thus has potentially access to the cryptocurrency. Just like with a bank , the user needs to trust the provider to keep the cryptocurrency safe. Trust was misplaced in the case of the Mt. Gox exchange, who 'lost' most of their clients' bitcoins.

Downloading a cryptocurrency wallet from a wallet provider to a computer or phone does not automatically mean that the owner is the only one who has a copy of the private keys. For example with Coinbase , it is possible to install a wallet on a phone and to also have access to the same wallet through their website. A wallet can also have known or unknown vulnerabilities. The sending party only needs to know the destination address. Anyone can send cryptocurrency to an address. Only the one who has the private key of the corresponding address can use it.

When the private keys and the backup are lost then that cryptocurrency is lost forever. When using a webwallet, the private keys are managed by the provider. When owning cryptocurrency, those trusted with managing the private keys should be carefully selected. An encrypted copy of the wallet should be kept in a trusted place. In order to initiate or verify a transaction, the cryptocurrency wallet connects to a client or node on the network to process the request.

There are several types of clients like: Some of them can process transactions and some of them also have their own wallet functionality. When the user of a hardware wallet requests a payment, the wallet's API creates the transaction. Then the wallet's hardware signs the transaction and provides a public key, which is sent to the network by the API.

That way, the signing keys never leave the hardware wallet. If a hardware wallet uses a mnemonic sentence for backup, then the users should not electronically store the mnemonic sentence, but write it down and store in a separate physical location. Storing the backup electronically lowers the security level to a software wallet level. Hardware wallets like LedgerWallet and Trezor have models that require the user to physically press or touch the wallet in order to sign a transaction, the destination address and the amount of coins.

The private keys remain safe inside the hardware wallet. Without the private key a signed transaction cannot be altered successfully. Some hardware wallets have a display see the picture where the user can enter a pin to open the wallet and where the transaction can be verified before being signed.

When reading a mnemonic sentence from the physical display of the hardware wallet a screencapture of an infected computer will not reveal the mnemonic sentence. With a watch only wallet someone can keep track of all transactions. Only the address public key is needed. Thus the private key can be kept safe in another location.

With a multisignature multisig wallet multiple users have to sign with their private key for a transaction out of that wallet public key address. With a brain wallet someone remembers the information to regenerate the private and public key pair s , like a mnemonic sentence.

Terms also used in the context of cryptocurrency wallets are hot and cold wallets. Hot wallets are connected to the internet while cold wallets are not. With a hot wallet cryptocurrency can be spent at any time. A cold wallet has to be 'connected' to the internet first.

As long as something is connected to the internet, it is vulnerable to an attack. The short version is that software wallets where the device is turned on or the wallet software is running are considered hot wallets. A not connected hardware wallet is considered a cold wallet. Deep cold storage is the process of storing cryptocurrencies in cold wallets that were never connected to the Internet or any kind of network.

Additionally the private keys associated with this system are generated offline. The process gained main stream attention, when Regal RA DMCC [21] , the first cryptocurrency licensed company in the middle east took it a couple of steps further by storing the cold wallets in the Almas Tower vault below sea level along with the company's gold bullion and insured the cryptocurrencies for full value.

With a deterministic wallet a single key can be used to generate an entire tree of key pairs. This single key serves as the "root" of the tree. The generated mnemonic sentence or word seed is simply a more human-readable way of expressing the key used as the root, as it can be algorithmically converted into the root private key. Those words, in that order, will always generate the exact same root key. A word phrase could consist of 24 words like: That single root key is not replacing all other private keys, but rather is being used to generate them.

All the addresses still have different private keys, but they can all be restored by that single root key. The private keys to every address it has ever given out can be recalculated given the root key. That root key, in turn, can be recalculated by feeding in the word seed. The mnemonic sentence is the backup of the wallet. If a wallet supports the same mnemonic sentence technique, then the backup can also be restored on a third party software or hardware wallet.

A mnemonic sentence is considered secure. It creates a bit seed from any given mnemonic. The set of possible wallets is 2 Every passphrase leads to a valid wallet. If the wallet was not previously used it will be empty.

In a non-deterministic wallet, each key is randomly generated on its own accord, and they are not seeded from a common key. Therefore, any backups of the wallet must store each and every single private key used as an address, as well as a buffer of or so future keys that may have already been given out as addresses but not received payments yet. From Wikipedia, the free encyclopedia.

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