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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1answer
386 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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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, ...
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1answer
82 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, ...
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2answers
215 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, ...
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2answers
155 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 ...
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1answer
122 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 ...
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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?
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1answer
778 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 ...
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1answer
3k 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 ...
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1answer
42 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 ...
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2answers
95 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 ...
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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. ...
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1answer
150 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 ...
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1answer
78 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 ...
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1answer
61 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?
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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 ...
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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 ...
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1answer
10k 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.
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1answer
672 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. ...
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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.
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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?
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2answers
281 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 ...
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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 ...
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1answer
141 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 ...
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1answer
395 views

How is a stratum connection secured?

Does stratum mining use something similar to "https" to secure traffic between the pool and the miners?
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3answers
356 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 ...
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11answers
58k 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 ...
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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
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1answer
443 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....
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2answers
129 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 ...
6
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1answer
584 views

If a single private key of the HD bitcoin account is compromised, is the whole HD account compromised?

The subject pretty much asks it all. I asked the same question on the Mycelium web site but did not get an answer. An HD account can have multiple private keys. Suppose one of the previous private ...
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0answers
419 views

Safely generating Bitcoin paper wallets [closed]

I'm new to Bitcoin and I have recently purchased a few fractions of Bitcoin. My BTC are stored on what I understand is an online wallet (a website where I log in using two-factor authentication and ...
3
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2answers
56 views

Querying UTXOs with random key pairs

As the number of transactions in the bitcoin network grows, the number of addresses with bitcoin will also grow. Is it possible for someone to “scavenge” for bitcoin by generating random key pairs and ...
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3answers
323 views

What happens if everyone discovers much faster way of solving hash function problem (mining)?

The question is not about how bitcoin mining works, but rather how bitcoin system adapts to progress in ability to tackle proof-of-work problems. Suppose that proof-of-work problems used for bitcoin ...
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1answer
110 views

Can a Bitcoin ( or any other cryptocurrency ) be compromised with a large botnet/s?

I'm new to cryptocurrencies, so I recently read the paper from the Satoshi Nakamoto ( link is here ) to know a little bit more about the Bitcoin.And I saw this statement: What is needed is an ...
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3answers
3k views

Which exchanges support U2F authentication? [closed]

I got myself a nice security key (Yubico Fido) today, which utilises the U2F protocol. But to my surprise not a single Bitcoin exchange seems to support this yet, only Google itself. So which ...
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1answer
712 views

Security risk(s) in running bitcoin core full node

What are the security risks posed by running a full node bitcoin core client? On a typical system, port 8333 is open and all other nodes can actually 'see' my machine and sites like https://bitnodes....
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2answers
238 views

Security implications of regular saving into cold storage

I am thinking about following this plan: Regularly buy bitcoins in an online exchange, 100€/month at market prices. Once the balance in the exchange exceeds a certain limit (500€), move those ...
3
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1answer
64 views

Is it better to compile bitcoin node or rather for some reason just use the official binaries?

As I have some doubts about a possible hackers' attacks on https://bitcoin.org/ Wanting to run a full node, I rather compiled the Bitcoin Core from git source for Linux instead. The question is: ...
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1answer
236 views

How to generate a paper wallet?

What do you find the best way to generate a paper wallet for BTC? I've heard of this one: https://keybase.io/warp/warp_1.0.9_SHA256_a2067491ab582bde779f4505055807c2479354633a2216b22cf1e92d1a6e4a87....
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2answers
555 views

Why is it safer to keep your bitcoins offline than online on Coinbase?

I'm trying to think of a good way to store my bitcoins somewhere but I can't really think of a way to do it without 1) having something physical (eg. USB key) that can get lost or destroyed 2) having ...
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3answers
1k views

How to make PoS system work?

In a r/bitcoin I've found the following statement: I think it should be noted that this paper covers a "pure" PoS system, but there have been some hacks to PoS systems to make them "work" (work ...
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0answers
109 views

Zcash proposal to use checkpoints to verify monetary supply [closed]

Based on concerns about the trusted setup not being able to conclusively disprove the ability to create hidden inflation, Zooko recently described an idea to institute checkpoints to verify the total ...
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3answers
48k views

Is it safe to store all my coins on Coinbase?

Is it safe to store my coins (BTC & ETH) on the Coinbase platform or is it safer to download a wallet to keep them in?
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4answers
1k views

Trezor Custom Mnemonic

How do I go about using words I pick in a trezor seed? I only want words that I select and in an order I select. I'm not worried about this being a less secure way to generate a seed. I will be doing ...
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3answers
663 views

Any need for coinbase field in coinbase transaction?

My understanding is that every block in the bitcoin blockchain has a coinbase transaction which contains a coinbase field. It is essentially an orphan field (placeholder) for use in claiming existing ...
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1answer
808 views

How to open new wallet into Bitcoin Core and switch between?

I have my old wallet which private key is compromised. So my reasonable way is to open new wallet and move all bitcoins from compromised wallet to new wallet. I use Bitcoin Core. I do not trust any ...
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4answers
704 views

Would bitcoin be destroyed if a wealthy organization obtained a CPU majority for a sustained period?

Inspired by this question ("Could bitcoin be destroyed by an entity cornering the market?") and the top comment on this answer to this question ("How much would it cost to execute a 51% attack?"). ...
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4answers
149 views

What can an attacker who controls majority or all of the full nodes do?

What happens when a strong attacker has control of majority or all of the full nodes? What damage can he do and would they be reversible?
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1answer
370 views

What is crypto-proof UTXO set?

There are many opinions about getting the actual UTXO set of blockchain. Do you think that this important database must be based on data which saved on disk and never modified after, only appended? ...