Questions tagged [security]

This tag should be used for questions regarding security issues with the design or implementation of Bitcoin and related cryptocurrencies.

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ECDSA x,y coordinate validity verification doesn't seem to work

The ECDSA algorithm, secp256k1 for Bitcoin allegedly uses the equation y ^ 2 = x ^ 3 + 7 mod P to determine the validity of an alleged point upon the elliptical curve. Utilizing http://web2.0calc....
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1answer
68 views

Delegated Proof of Stake (DPOS) vs. Proof of stake?

What is the main difference between Delegated Proof of Stake (DPOS) vs. Proof of Stake? Is there any significant advantage for security? (since PoS in general suffers security problems.) And which ...
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3answers
531 views

Is creating a long password for my coinbase account enough to keep my bitcoins secure?

I've made an account with coinbase and purchased some bitcoin. Only after to start reading people talk about getting hacked and how bitcoins are not secure unless you put them in a "wallet".To be ...
0
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1answer
25 views

Statement: for an attacker to change history, they must solve computational puzzles at a faster rate than the rest of the participants combined

I'm new to cryptocurrency and blockchain. I just started reading the textbook Bitcoin and Cryptocurrency Technologies by Narayananm, Bonneau, Felten, Miller and Goldfeder. The statement in the title ...
3
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1answer
43 views

Question about identical txids/merkle tree in Developer guide

I am new to the technical details about Bitcoin and has been reading Developer guide on bitcoin.org. I have a question about below contents mentioning merkle tree, identical txids. I googled and ...
2
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2answers
58 views

Do lightweight wallets validate signatures? If not, why?

I've learned that "some SPV clients simply don’t check signatures themselves at all": https://bitcoincore.org/en/2016/01/26/segwit-benefits/#efficiency-gains-when-not-verifying-signatures I wonder if ...
3
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1answer
837 views

How does timejacking enable double spending?

http://culubas.blogspot.com/2011/05/timejacking-bitcoin_802.html I went over this blog, but I am still not clear how double spending is achieved by this attack. From what I read, the attackers submit ...
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0answers
23 views

How to protect a crypto currency from Seed failure

I have created a new currency based on Forknote/Cryptnote. It has a small number of Seed Nodes. I am investigating how to mitigate the risks of currency failure due to Seed Node collapse from ...
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2answers
42 views

Trading crypto currencies with dollars

After I have bought a crypto currency at an exchange like Binance can I sell for dollars if it is going down. Basically if I have a profit from a currency what can I do with it to protect it?
5
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1answer
396 views

How can all possible numbers in 256-bit space be squeezed into 160-bit space?

Bitcoin addresses are essentially 160-bit hashes of a 256-bit public key. Huh? How can all possible numbers in 256-bit space be squeezed into 160-bit space? Does that mean any given bitcoin address ...
2
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1answer
150 views

Is there a limit to how many blocks can be rolled back from a 51% attack?

I was wondering if we where to ever face a 51% attack is there some sort of limit as to when the longest chain doesn't matter? For example if I owned 51%+ of the network, mined 1000 blocks privately ...
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3answers
148 views

Has PoS really been proven secure under comparable assumptions as Bitcoin?

I am just reading this paper which claims to be a formal proof that Cardano's latest Ouroboros PoS protocol ("Genesis") gives similar security guarantees than Bitcoin's PoW protocol. Unfortunately, it ...
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1answer
2k views

How to hack a Password of Private Key

I have a Private key and then after I entered it, there's another saying "Input a required Password of Private Key" So how can I hack or generate that?
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1answer
44 views

Possibility of broadcasting new block to only a fraction of honest nodes?

Consider in a block-withholding attack (aka selfish mining attack), attacker after creating a new block decides to broadcast this new block only to a fraction of network, such that eventually only a ...
0
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2answers
108 views

How to secure a Linux node running satoshi 0.16.1?

Everyone in the BTC space seems to suggest that running a full node is the way to go. But Linux has a huge attack surface and I don't want to lose my BTC by having my wallet on an insecure OS. What is ...
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3answers
241 views

How can Bitcoin be stolen?

If each bitcoin has a ledger (Peer to Peer) and contains all the transaction history since it was mined, then how come it can be stolen? For example, Bitcoins were stolen by hackers from Mt. Gox. If ...
7
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2answers
691 views

Can the blockchain be outpaced by a chain of low-difficulty blocks?

Let's say someone creates a blockchain fork starting from the genesis block, when the difficulty was absurdly low compared to today; then he starts mining new blocks from there up to the current block ...
7
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1answer
1k views

What happens if my wallet gets “hacked” and my BTC is stolen?

What if my wallet gets hacked and the hacker transfers all BTC to his account? Is there is any way to get it back, or to open a dispute to specific address or anything else?
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6answers
1k views

How do I protect my paper wallet from use by a different human who has used a random generator?

Since millions of people use Bitcoin and Bitcoin Wallets that use their own addresses use several addresses per day, it is obvious that generators can generate the same characters for the Bitcoin ...
4
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3answers
2k views

How is the lightning network secured against hacking and double spends?

As I understand payment-channels, like the lightning network, they are working off chain (no record in the blockchain). The only record to the blockchain is the deposit transaction to open the payment-...
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2answers
100 views

i lost access to my bitcoin [closed]

I did not have any idea about bitcoin but I wanted to get in, I met this guy who knew about it on facebook asked him if he could help. he sent me the link on blockchain to signup showed me how to buy ...
2
votes
1answer
71 views

Checking the first and last characters of a cryptocurrency address?

When confirming that an address entered on a site/app is what I expect it to be, I often check the first and last 3-4 characters to see if they match. Is this practice dangerous? Could an attacker ...
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2answers
550 views

How to securely store Bitcoin server-side?

I am working on a web application that needs to hold users Bitcoin for an extended amount of time (escrow-like scenario), and I was wondering what are some good steps/precautions and principles (dos &...
3
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1answer
57 views

Why is it more profitable for a node with more than 51% computation power to abide by the rules in the bitcoin network

The Bitcoin whitepaper states - "The incentive may help encourage nodes to stay honest. If a greedy attacker is able to assemble more CPU power than all the honest nodes, he would have to choose ...
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3answers
377 views

How safe is it to use online wallets? [closed]

I want to know if it is safe to use online wallets? Can we trust online storages which stores our privkeys, passphase and wallet.dat files? I read that at least one android wallet was hacked so I ...
4
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1answer
228 views

How do the JavaScript SecureRandom() vulnerabilities affect me?

A recent post on the Bitcoin-dev mailing list talks about multiple vulnerabilities in JavaScript SecureRandom() class. Apparently this class has been used in multiple cryptocurrency wallets that use ...
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0answers
109 views

Trying to figure out the two-part authentication process. Can anyone give direct instructions?

I'm using btc-e.com verification, in the Finances section. It supplies two key codes and has a square bar code to scan. I've set up my google account for two-part verification, and google is ALSO ...
14
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2answers
6k views

What is a block withholding attack?

How can a block withholding attack be performed, what would be its purpose and who is it a danger to? Edit: when I posted this I was thinking about withholding a block you mined in a pool. But ...
23
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3answers
5k views

Can one safely buy vanity addresses from a third party without risking one's coins from being stolen?

One can easily generate vanity addresses for Bitcoin, but they can take quite awhile to generate. Outsourcing that process to someone with a strong mining rig is an option, but then one runs into the ...
52
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4answers
30k views

What keeps the average block time at 10 minutes?

I've been told "the network" sets the difficulty level such that there will be one new block mined every ten minutes. I imagine the rich would instead prefer to keep difficulty as high as possible to ...
50
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9answers
5k views

What methods could a government use to shutdown Bitcoin?

Let's say that a government decided to shut down the Bitcoin network. What options would they have to achieve this? Would they need to convince other governments? All governments? Let's set as a ...
0
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3answers
50 views

Am I protected?

I've been asked to pay for a purchase in Bitcoin. Why would someone use this method instead of say Paypal and as a consumer am I protected in any way? I have never used Bitcoin or looked into it so I'...
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3answers
146 views

How can I safely store and trade Bitcoin and other crypto currencies?

How can I safely store Bitcoin? Exchanges require me to deposit to trade, is this safe? If I can't trust exchanges, what is the best way to safely store my cryptocurrency and transact it?
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1answer
50 views

Given that you have the necessary computing power, how does a tampered blockchain get accepted by the network?

I read that you can only tamper with a blockchain if you have more than 50% of the computing power in the network. So say you have 51% of the computing power, then you can create a longer blockchain ...
37
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7answers
49k views

How long would it take a large computer to crack a private key?

I am doing a presentation on Bitcoins and I was looking for some calculations to make people feel safe about the private key encryption. Please first answer, how long in bytes the private key is, ...
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1answer
65 views

Is Lightning network really a hope for better scalability and low latency?

BTC can't do transaction in 1/4000 times to what VISA does and then still claims that it will disrupt industry. The proof of work has limitations to scalability and in no way it can record transaction ...
2
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1answer
57 views

Why is it important that miners mine at the end of the longest branch?

In this paper, the authors present a simplified description of mining strategies. The strategy which they call "honest strategy" is to always mine a block at the end of the currently longest branch. ...
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1answer
56 views

What prevents a node from sending a different version of the blockchain?

I understand that proof of work prevents a node from creating a new version of the blockchain unless they have >50% of the hash rate, but what if the attacker is also able to intercept the victim's ...
19
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2answers
3k views

How does a client decide which is the longest block chain if there is a fork?

Is it only the block height or is it the effort that went into the forks? In other words: does this decision account for different difficulties?
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2answers
79 views

Which one is more effective for attacking the system, controlling 51% of the mining power or 51% of the full nodes?

I used to think it is the miner who verify the transaction, but it turns out this is really a joint work by the miner and the full nodes; the miner broadcasts the newly discovered block, which ...
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1answer
80 views

Could BitCoin network be destroyed if blockchain would get corrupted?

This thought came to me whilst watching mr. Robot where the entire database of a financial corporation has been encrypted. Would that (in theory) be possible if a virus was spread that would target ...
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1answer
132 views

Why do the biggest exchanges reuse Bitcoin addresses if doing so is unsafe?

It's generally accepted that using one address for multiple transactions is unsafe, because sending a transaction reveals your public key (whereas only the hash of your public key is required to ...
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1answer
32 views

How bitcoin wallets connected between

I'm thinking, is it dangerous to buy bitcoin, in case if government want to block it? How bitcoin wallets connected between? If I'm right - there are support servers, who providing connection between ...
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6answers
365 views

What would a new exchange need to be better than the rest?

If a new crypto v crypto exchange were to be built and launched. What would tempt you to use it rather than what you currently use? Or what improvements would you like to see from the way things work ...
0
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1answer
90 views

Is it more dangerous when 51% attack happens than just having a pool with >50% hashrate?

Many people told me that, if a mining pool performs a 51% attack, the price of the coin will drop. But I disagree. There are pools with >50% hash power already for a long time. Flypool is an example....
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2answers
119 views

What are the implications of a huge amount of unused hash power?

A not unthinkable scenario is that the Bitcoin price decreases to, say, 10-20% of today's value. This would make mining less profitable, and the difficulty should adapt accordingly. This should lead ...
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1answer
275 views

A theoretical low cost attack scenario in PoW currencies

The scenario was designed by user:croraf and me in discussing a question of mine yesterday. To make it more clear, I want to present it here again in a stricter design. To do it in a clear way, first ...
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2answers
114 views

What prevents broadcasting of fraudulent transactions

I see a lot of questions and articles about why someone can't generate fake coins, maliciously attack the network, and essentially security discussions focused on the generation and interception of ...
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1answer
72 views

How Bitcoin wallets avoid address re-usability?

As we know, address reusability compromises both privacy and security. My question is how Bitcoin wallets avoid address reusability? Is wallet generates an address from index 1 and scan blockchain ...
12
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1answer
271 views

What security features are built in to the standard Bitcoin software?

I have read much of the Bitcoin algorithm and its encryption basis, however little has been said of the software's inherent security. What solutions are already built in to the software, and what is ...