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Questions tagged [security]

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

25
votes
3answers
36k views

What is a double spend?

What is a double spend? As someone who uses Bitcoin, what do I need to know about how the Bitcoin system prevents double spends? Are there still circumstances where they can occur?
1
vote
1answer
178 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 ...
1
vote
2answers
434 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 ...
0
votes
1answer
114 views

How would one go about acquiring the HashofThingtoSign from this old transaction?

How would one go about acquiring the HashofThingToSign that is used in the "Signature Generation" equation for this example transaction such that it could easily also be applied to any other given pre-...
1
vote
1answer
371 views

What would happen if a mining pool admins having majority of hash power turns evil?

This question interest me mostly in the context of the Ethereum, but it might be interesting to see how this problem is solved by the other cryptos as well. I understand that the consensus about what ...
5
votes
4answers
1k views

How to redeem a private key in case it is compromised

I know MtGox allows me to redeem a private key, but that doesn't necessarily ensure that all the value is extracted from that address in a timely manner. Is there no simple way to send the entire ...
0
votes
2answers
289 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 ...
1
vote
5answers
795 views

Are Web Wallets Secure?

I normally keep only small amounts in a web wallet because I heard that web wallets are not secure. The rest of my Bitcoins are kept in cold storage in my safe. I'm just wondering if you have any ...
1
vote
1answer
283 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 ...
2
votes
2answers
998 views

Is it possible to use the same BIP39 list of seed words to create addresses for different crypto assets?

Currently, as a matter of convenience, I'm holding small about of crypto assets on various exchanges. It's not ideal - I'd much rather store them locally, have access to the private keys, be in full ...
14
votes
3answers
4k views

Which Two-factor authentication methods are available at which exchanges?

I see that Mt. Gox now supports the Google Authenticator app (on Android, iOS - iPhone, iPad, iPod Touch, and on Blackberry) for 2-factor authentication (in addition to support for Yubikey, of course)....
4
votes
1answer
182 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 ...
1
vote
2answers
2k views

Ripple paper wallet: is “ripplepaperwallet.com” safe?

I've been reading on the internet and I have found several websites for generating Ripple paper wallets: ripply.eu, bithomp.com, gatehub, etc. I'm not sure if these websites are official Ripple ...
32
votes
1answer
51k views

How can I restore my wallet?

I just purchased a new laptop and I want to decommission my old one. I have a back-up of my wallet.dat file copied to my new PC. What do I need to do to restore it to my Bitcoin (Windows) client? ...
1
vote
1answer
52 views

How do I know if the Bitcoin page has been hijacked [closed]

With so many hackers hijacking websites these days, what do I look for to show me that I'm not on a hijacked page?
0
votes
1answer
147 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 ...
0
votes
1answer
293 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 ...
0
votes
1answer
37 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 "...
2
votes
4answers
307 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 ...
0
votes
1answer
337 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?
0
votes
1answer
2k views

scammed by a scammer [closed]

First of all, this is to bring awareness of how an attacher may gain access to a persons' Blockchain Wallet: i hope this never happens to anyone else but it probably will. i am quite new to bitcoin, ...
0
votes
1answer
79 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, ...
1
vote
2answers
184 views

What prevents a miner to change the locking scripts of an unconfirmed transaction

In many cryptocurrencies a TX is composed of an array of TX inputs and TX outputs. When a TX is submitted to the network, it already has the signature (in the unlocking script). So my question is, ...
0
votes
2answers
145 views

Extra security for paper wallets

I want to transfer my bitcoin to a paper wallet for long term storage. However, with the risk of fire/theft etc. I'm not comfortable holding it as a paper printout. So my question (sorry if its too ...
3
votes
1answer
121 views

Is my wallet effected by the Meltdown and Spectre vulnerabtilies?

Recently two new vulnerabilities, Meltdown and Spectre were published which lets someone read more memory than they are supposed to be able to. How does this effect my wallets and what can I do to ...
1
vote
3answers
6k views

What are the advantages and disadvantages of 24/7 Bitcoin trading?

What are the advantages and disadvantages of 24/7 Bitcoin trading over traditional stock market which operates only 6 - 8 hours a day and 5 days a week? Any threats?
20
votes
1answer
767 views

Gaming the “off-by-one” bug (difficulty re-target based on 2015 instead of 2016 block time span)?

In this forum post from Gavin Andresen he writes: Second: I've written 'discourage blocks' infrastructure: https://github.com/gavinandresen/bitcoin-git/tree/discourageblocks (code reviews ...
-1
votes
1answer
2k views

How can I cancel a pending transaction

https://blockchain.info/tx/d2aa8e971dd26a4f4598f57b55e921a62fa376dad1cf25e426b6ba7d79052466?show_adv=true. This transaction was made by some fraudsters on my wallet. I later recovered my wallet. How ...
1
vote
1answer
658 views

How will Lightning Network nodes secure their hot wallets?

The success of the Lightning Network is dependent on payment routing. Successful payment routing will require online nodes with automated signing facilities. This entails online nodes with hot wallets....
0
votes
1answer
40 views

Storing wallet key for automatic transactions

Is there any way to do this? For example I don't even want to know what my wallet is, only my server (intranet), so that it can make automatic transactions for me based on thresholds. Or should I not ...
0
votes
2answers
93 views

are individual satoshis as secure as an overall bitcoin?

I don't really understand Bitcoins as well as I'd like. I understand that eventually there will be 21,000,000 bitcoins mined. And, I understand that each bitcoin can be subdivided into 100,000,000 ...
1
vote
1answer
42 views

Month into crypto and have some questions

I've been invested in btc, eth, and ltc for about a month on Coinbase. I'm still working to learn about this expansive realm. I don't totally understand the need for a wallet and how that works. ...
9
votes
1answer
149 views

How can vulnerabilites in bitcoin be responsibly reported?

I am wondering if someone discovers a bug/exploit in Bitcoin software or protocol, who should it be disclosed to? Who is the authority? What would happen if the bug went public? Has it occurred in the ...
3
votes
1answer
77 views

How the Bitcoin community will handle attacks on a Client's code?

I have some thoughts about the following scenario. The brightest future. The Bitcoin becomes a very popular and liquid currency all over the world. Some serious financial or political parties may ...
1
vote
1answer
60 views

Transforming existing private key into new private key?

Is it possible to derive a new private key from an existing private key and retain the same bitcoin balance without any transactions?
2
votes
1answer
4k views

Is it safe to authorize Coinbase to withdraw cash directly from my bank account?

I wanted to buy Bitcoin. Coinbase said that they could transfer money directly from my U.S. bank account and convert it to Bitcoin, and then I'd have a Bitcoin address and could give people Bitcoin or ...
13
votes
6answers
7k views

How can I stop websites running an integrated Bitcoin miner without disabling javascript altogether?

"Bitcoin Plus" is one example of a javascript bitcoin mining client that can CPU mine bitcoins through a browser when viewing a website. Here is a screenshot from 4bitcoins dot com which automatically ...
11
votes
1answer
9k views

How to download bitaddress.org to use offline?

The site does not have a download option. I can save the page using Google Crome by CTR-S, but the version I have saved in this way does not work.
1
vote
1answer
659 views

Bitcoin is becoming CENTRALIZED and is INSECURE [closed]

I'd like someone to tell me if I'm wrong: More than 50% of the mining is done by Chinese pools. That means that they control the network - who's transactions get in, who's transactions are left out. ...
11
votes
1answer
1k views

Is it a 51% attack or a >50% attack?

Is it 51% attack or 50.0000...1% attack? Bitcoin is getting to a point where 1% is a lot of hashing power... My understanding is >50% due to the nature of the protocol.
7
votes
3answers
5k views

How do I know that my bitcoins are real

I have bought some bitcoins off local bitcoins and stored them in an Electra wallet in my computer. Given that I have now paid hard cash, how am I to determine that these are real?
1
vote
2answers
275 views

Why don't the miners just take profit from our coins and make the coin worthless?

You own a very valuable thing and you want to go to holiday without it, but there is nobody who you trust and who can look after the thing. So you take somebody unknown to guard it. You pay him a fee ...
2
votes
1answer
603 views

Are received BTCs really mine?

when somebody send me BTCs I recognize that by seeing a transaction output is equal to my address. But how can I be sure that it's really me and only me who can spend the output? I can check, I can ...
0
votes
1answer
138 views

What would happen if every miner adds a transaction to his block that did not occur?

Let's say every single miner in the world added the same transaction to their block via trickery. The transaction was never initiated by the wallet holder. Would a block from these miners be added to ...
3
votes
1answer
370 views

How is a stratum connection secured?

Does stratum mining use something similar to "https" to secure traffic between the pool and the miners?
4
votes
3answers
351 views

Egoistic miners combined with large transactions destroy PoW?

EDIT There is a clearer description of some parts of the problem in the link questions. If there is a transaction value much higher than the payment for mining 10 new blocks, how can you trust this ...
114
votes
11answers
56k views

Is it possible to brute force bitcoin address creation in order to steal money?

Bitcoin users frequently generate new addresses for each transaction they make, which greatly increases the number of bitcoin addresses being used to receive money. Would it be possible (and ...
26
votes
5answers
2k views

How much would it cost to execute a 51% attack?

I know that it's commonly said that they're not really in the realm of possibility right now, but how much would it really cost to execute a 51% attack on the network? And are there any organizations ...
2
votes
1answer
385 views

How to verify the Bitcoin core software?

I just installed Bitcoin core (v0.15.1) for the first time. I've read that it's best to verify the software after downloading, but I don't see the links that are referred to in the instructions/videos....
1
vote
2answers
127 views

Eliminating all private keys records from pc

Suppose I buy a new wifi router and a new pc. I set up both the wifi network (of course, with a password) and the pc. Now I access the internet for a few seconds in order to download bitaddress.org ...