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

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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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1answer
746 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
9 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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1answer
34 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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1answer
24 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 ...
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1answer
377 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 ...
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2answers
25 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
95 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
26 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 ...
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2answers
58 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
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1answer
43 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 ...
2
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1answer
45 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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1answer
70 views

Is possible to destroy the Bitcoin for just $500K? (51% attack)

Everytime I read about the 51% attack the answer was something like: is really expensive to get 51% of power on BTC and nobody will invest so much so to destroy the bitcoin. But I found this site ...
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1answer
95 views

Hello, someone is using an bitcoin account to blackmail me [closed]

Someone using a bitcoin account is trying to blackmail me. The account number is 1Mtsd3wXgkJnApaNpqaSSWLC6gCLBBxuaGG. I still have the email they sent me. I can also provide that email if needed, or I ...
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1answer
701 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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3answers
43 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
116 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
37 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 ...
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1answer
42 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 ...
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1answer
557 views

Private key to mnemonic words, is it safe?

Is it safe to do the following? Suppose I do not want the HD wallet, but I do want the convenience of using mnemonic words to remember the private key. I know I can convert the private key's hex ...
0
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1answer
63 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
30 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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1answer
190 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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2answers
1k views

How do you derive the private key from two signatures that share the same k value?

I wrote my own ECDSA signature algorithm just for the purpose of creating unit tests. With it I created two signatures which went into transaction 56ec7ca7df..., sending from 1GXFXm3es.... These ...
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2answers
50 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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2answers
31 views

What Happened 12/30/17 Last Recieved Transaction into Bitcoin Core Wallet

I have found a different receiving address within my wallet that is not mine... at least I did not create it. It seems to me that all of my transactions are now going to this new address instead of ...
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1answer
68 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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3answers
873 views

Miner modifies unconfirmed transactions and put it into the block

Is is possible that a miner modified a unconfirmed transaction (like changing the output of transaction to the miner himself) and put it into the local block, and after 10 mins the miner luckily ...
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1answer
60 views

Is “fee higher than block reward” attack possible?

Imagine the following scenario: I send you 1000 BTC. After 6 confirmations, you give me what I bought. I create another transaction with 900 BTC to my own wallet and 100 BTC as transaction fee, using ...
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1answer
71 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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1answer
108 views

What bad things could happens if Bitcoind RPC is public?

It is always suggested to enforce authentication on Bitcoind RPC. However, in case the RPC authentication get compromised (or if it is public), what kind of bad things could happens? First I could ...
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1answer
54 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 ...
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1answer
119 views

Forking Bitcoin how to prevent a 51% majority attack

Lets say I fork Bitcoin, to lets call it StackCoin. How do I prevent a 51% majority attack when miners are not in abundance? Would I have to setup a lot of miners to create the infrastructure of the ...
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2answers
160 views

How to check if a program is mining crypto in the background

I noticed a program I recently downloaded cause my CPU usage increase by 30 percent and 80% GPU usage increment in idle state. It is not a GPU intensive program at all. I am worried about it using my ...
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0answers
136 views

Are DAG-based crypto currencies as secure as proof-of-work based blockchains?

A key feature of blockchain based cryptocurrencies is that they provide inherently secure systems that don't rely on third parties. The newer DAG-based cryptos like Byteball are being touted as ...
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2answers
32 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?
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2answers
178 views

Private key security level

Any of a kind Bitcoin wallet need to share private key on the internet-connected machine. Bitcoin client has no responsibility for to keep private key secure. If your's machine connected to the ...
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2answers
3k views

Binance hacked?

Something is happening, yesterday in reddit many people could not withdraw their funds or cancel their purchase orders . And the administrator (who is binance and usually solves the problems) erased ...
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0answers
44 views

How does the bitfury crystal software works?

Can someone explain to me how the crystal software works? The transfers made using multiple wallets are anonymous and not traceables?
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1answer
164 views

Safely transferring from a paper wallet [closed]

I am holding for the long term and have a significant amount of bitcoin (~10) in a paper wallet (the actual private key is printed on a piece of paper). To improve security measures and possibly sell ...
5
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1answer
112 views

In what sense does the security model of proof-of-stake require users to “log on to the internet every few months”

This is primarily a question about something I heard Vitalik Buterin say in an interview the other day. (Unchained podcast's January 9, 2018 episode, at 34 minutes, 15 seconds) I quote: As far as ...
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1answer
65 views

Why doesn't Multisig provide better security for hot wallets?

I've recently read somewhere (can't remember the source) that multisig often doesn't provide more security in hot wallets, but increases the size and thus the fee. I can't seem to comprehend how ...
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1answer
167 views

Who maintains list of bitcoin nodes and aren't they a weak link in the security of the system?

I understand that between the people who run Bitcoin nodes, and therefore the Bitcoin protocol, the system is trust-less and secure. However, there seems to be a weak link - the official list of ...
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2answers
66 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
35 views

Can a cryptocurrency be “decapitated”

Say the first n blocks on the block chain were mined by the creator of the currency. What's to stop everyone unanimously deciding to ignore those first n blocks at a later date and therefore "...
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4answers
164 views

Is it wrong to spend Bitcoin from someone else's wallet if my Bitcoin client generates the same address?

I know this scenario is extremely unlikely but what-if by chance I get the same Bitcoin address as another user and the user has hundreds or thousands of Bitcoins in his wallet, is it morally/legally ...
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1answer
565 views

Is it possible to bruteforce the seed?

Is it true that the "seed words" bruteforce more reliable for to get profit than searching of a "random number" for to open some profitable outputs? The last one is impossible due to math, but the ...
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1answer
166 views

Lost my phone with the wallet in it… Any way to recuperate my 5.178 bitcoins? [closed]

Phone and car got stolen, i had the keychain of my wallet on a pad, so it's all gone, everything!! Please tell me there's a way to get them back?
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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 ...
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1answer
61 views

Non-Bitcoin blockchain security questions

I've been seeing a lot of stories lately about companies wanting to use blockchain, I've got two questions regarding companies using blockchain networks to store transaction ledgers. With Bitcoin, ...