96

It is possible to brute force some Bitcoin addresses, because some people generate their private keys in an insecure manner. Any (non-zero) 32 bytes can be a private key. So running sha256 over a passphrase gives an apparently random, but brute force-able private key. Take sha256("sausage") for instance: $ echo -n 'sausage' | sha256sum ...


51

In order to spend money sent to a Bitcoin address, you just need to find a ECDSA public key that hashes to the same 160-bit value. That will take, on average, 2160 key generations. Supposing you could generate a billion (230) per second, you need 2130 seconds. Doing this in parallel using a billion machines requires only 2100 seconds. Getting a billion of ...


41

You have a good discussion in: https://bitcointalk.org/index.php?topic=133425.0 Basically, ECDSA is compromised, hashing isn't. With a quantum computer, you could easily deduce the private key corresponding to a public key. If you only have an address, which is a hashed public key, the private key is safe. Anyway, to spend a transaction, you need to send ...


27

If you were a miner, what are the steps you would take to create the extra (21,000,012.5th) bitcoin? Where in the source code is this exactly (link)? There are two components to CVE-2018-17144. There is a crash bug and an inflation bug. Both are triggered by almost the same scenario: a transaction contains an input multiple times. In general, how this ...


25

I think the best way of analyzing your question would be to break the destruction of the Bitcoin into categories. There is the notion of a hard destruction meaning an attempt is made to physically compromise the Bitcoin network either by a 51% attack or international legislation. And there is the notion of a soft destruction, where attempts are made to De-...


19

Worst case scenario: Bitcoin ECDSA algorithm would be broken. Because quantum computers can easily decrypt the private key using the public key, anyone with a quantum computer can extract Bitcoins using the corresponding public key. Bitcoin hashing would become exponentially difficult. There's already a predicted escalation in mining difficulty due to the ...


15

Bitcoin becomes very insecure if miners stop mining. Think of how easy a 51% attack would be to pull off. However, I disagree with your assumption that miners will stop. And certainly that if Bitcoin dies it would be because miners stop. I would instead think that miners would only stop if something else already killed Bitcoin. Bitcoin is designed to always ...


14

The exchange rate at any one point in time is determined by supply and demand at the markets. The value of all bitcoins at the current market price is $80 million because the current market price is the point where the demand for bitcoins at a certain price meets the supply. You are describing introducing an artificial demand that would indeed cause ...


10

If you would like to see some proof to verify that it is truly quite impossible to generate a known keypair, you could test this yourself, if you wanted. Pavol Rusnak has created coinkit, a python library for interacting with Bitcoin related stuff. In there, there is an example on how to use it that does exactly what you are asking. What it does is it ...


8

The process of attempting to buy all of the currency would drive the price up arbitrarily high. For example, I have some bitcoins and plan to sell 10% of what I have left every time the price doubles. I will never run out of bitcoins to sell, no matter how high the price, so it is impossible for anybody to buy them all. The US government could try to ...


8

These are Ripple's largest known weaknesses (not including weaknesses common to Ripple and Bitcoin): Because the Ripple network can't move actual fiat currencies, balances in Ripple act like bank balances. If the bank somehow defaults on its obligation, people won't actually have the money they thought they had. This is not a big problem if you're just ...


7

Have a look at the early sources here: http://www.bitcointrading.com/forum/bitcoin-clients/original-bitcoin-source-code-archives/ there is a small piece of code in script.cpp: case OP_RETURN: { pc = pend; } break; which allows to spend ANY UTXO with just a very simple scriptSig OP_1 OP_RETURN


7

Only Copay is affected by this vulnerability. Although the package was included by many, many projects (both within and outside the crypto space), the attack payload was encrypted, and used the package description as a decryption key. They key in question was found to be (via brute force) A Secure Bitcoin Wallet, which is the npm description for the copay-...


6

I appreciate the enthusiasm of those who have answered this question. Everyone here clearly wants bitcoin to succeed, and so everyone is enthusiastic. I am enthusiastic, too. I am afraid, however, that this enthusiasm is coloring respondents' logic. Literally every response on this page (especially the highest ranked one) is wrong. In order for a ...


5

Currency exchanges are implemented through programs called order-matching engines. When a new order is entered, a buy order for example, the matching engine checks to see if there is a match on the other side, a sell order at the right price. Bid is the price a user is willing to pay and Ask is the price at which a seller is willing to sell. The difference ...


5

I believe Satoshi was once asked this question, and answered that it was just some curve that existed and was presumed to be efficiently implemented. I'll try to find a reference.


5

You could easy manipulate a pool to wreck havoc on other SHA256 coins if you owned it or managed to gain access. You don't even need to be a large pool, some altcoins are really small and vulnerable. It has affected other coins before, where a pool or a large miner created trouble solely by mining a smaller altcoin. Feathercoin hit by massive attack Only ...


5

In Bitcoin, inner nodes of the merkle tree are constructed by concatenating two 32 byte SHA256d hashes together. The resulting 64 byte value is hashed to get the next node in the tree. The leaf nodes are the transactions themselves. Merkle trees are used to prove that a transaction is part of a block as the merkle root is placed in the block header for the ...


4

There is the LBC (Large Bitcoin Collider) project that attempts to do that. According to their website they've created over 8,000 trillion keys, as of October 2017. According to a Motherboard article of April 2017, LBC found over 30 Bitcoin private keys.


4

It's impossible to tell the difference between bitcoins that have been lost forever and bitcoins that are being hoarded, so the US government would never be able to tell when they had bought all available bitcoins. And they're going to have to offer a lot more than the current market prices for some people to sell.


4

With unlimited money, you could destroy almost anything. I don't really see why it matters. If someone with unlimited money spends a few billion dollars to destroy Bitcoin, we'll just create Bitcoin2 and maybe he'll spend another few billion destroying that. We can keep creating new crypto-currencies indefinitely. If each one gets a few billion dollars out ...


4

One of the questions you linked to has the wrong chosen answer— Bitcoin can also be destroyed by a sufficiently deep pocketed attacker which corners sufficient marketshare of coins to enable causing debilitating volatility. Probably won't require any where near majority share to create volatility. I added my claim at that question. Yes Bitcoin can also be ...


4

The transactions will likely never be included in a block, as they do not meet the defacto bitcoin transactions rules for transactions sent without a fee, detailed here: A transaction may be safely sent without fees if these conditions are met: It is smaller than 1,000 bytes. All outputs are 0.01 BTC or larger. Its priority is large ...


4

It's entirely up to the people living at this hypothetical future point. There's no current rule about what happens. Maybe when this happens, people are tired of Bitcoin, so they go back to trading seashells. Or maybe when this happens, there's something better than Bitcoin available, so they all switch to that. Or maybe they just restart Bitcoin and ...


3

Edit: I no longer think this answer is true. The blockchain wouldn't cease to exist if an evil organization got a majority of hashpower. Thus, your questions would be better stated as, "If an evil organization that wanted to destroy bitcoin got a majority of hashpower, would bitcoin become less useful?" Yes, and we'd have to switch to an alternate scheme ...


3

See the hardfork wishlist on the Bitcoin wiki.


3

just some ideas: Strategies could be attacking the trust structure of bitcoin: Buying large quantities of bitcoins and dropping them on the market causes it value to fluctuate and make it appear weak hacking peer sites (like mtgox), or bitcoin users directly (via trojans, etc.) leaves insecurities on where to use it influencing media to emphasize about ...


3

Bitcoincard will use mesh radio network, but still, the transactions will be propagated to internet at first opportunity. However, one bitcoincard gateway with working internet access in whole city/neighborhood should be sufficient to prevent network forks.


3

The Bitcoin client is designed as a peer-to-peer network. To join the network, you need to make a connection to a node that accepts incoming connections. To protect against certain types of Sybil attacks, a client tries to make 8 outbound connections to geographically diverse nodes. If you connect to the network through tor, you cannot accept inbound ...


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