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25

ECDSA signatures are pairs (r,s) where r=(kG).x mod n, and s = (m + rx)/k mod n, where x is the secret key, k is the random nonce, and m is the message. If you have two s values s1 and s2 for the same secret key and with the same nonce k (and thus the same value r), the following holds: s1 = (m1 + r*x)/k s2 = (m2 + r*x)/k From that we can derive: s1 * k =...


12

The thing to consider is, "what does the attacker have to give up in order to attack me?" If the cost of that thing is less than the reward from a successful attack, then attacking is rational from a purely economic standpoint. (Obviously, attacking someone comes with a non-economic moral cost.) A miner who controls more than half of the network hash rate,...


7

Bitcoin uses SHA256 followed by RIPEMD-160, which I'll collectively call HASH160. Good hashes have 4 properties: it is easy to compute the hash value for any given message it is infeasible to generate a message that has a given hash it is infeasible to modify a message without changing the hash it is infeasible to find two different messages with the ...


7

There are about 2^256 private keys, 2^256 public keys, and 2^160 (simple) addresses. There are other addresses (multisig) that have more than one corresponding public key and thus more than one corresponding private key. 2^160 is 1,461,501,637,330,902,918,203,684,832,716,283,019,655,932,542,976. Just to put that in perspective: Number of stars in the ...


6

Don't worry, you've not been hacked. This is just one of your wallet's change addresses: https://en.bitcoin.it/wiki/Change How does change work in a bitcoin transaction? Why does Bitcoin send the "change" to a different address?


5

Your question indicates certain misconceptions about what Bitcoin is. I would advice you to take an afternoon to read the Bitcoin whitepaper, learn from other sources and understand as much as possible. It is possible to know what Bitcoins truly are without great technical knowledge. (Bitcoin transactions can only be made with the owner's private key. A "...


5

They anticipated this type of attack and they are monitoring their JavaScript files, check this website of theirs http://blockchain-status.com/javascript_verifier Also, CloudFlare (the reverse proxy they use) can modify the Javascript on the fly (CloudFlare is at the other end of the encryption for your browser, so SSL here only secures the connection ...


5

Once your client finishes downloading the block chain then everything should show as confirmed.


5

No, 58^34 is greater than 2^160: http://www.wolframalpha.com/input/?i=2*160+%3E+58*34 Note, that the address also contains a checksum and a network id not carrying additional information. That's why the numbers are not equal.


4

Bitcoin Armoury is the best thing out there for this. What you want to do is create a new wallet with armoury, create a receiving address and send your BTC there. The best thing is you do not need to even be connected to the network, synchronized or anything. Armoury can run offline in the dungeons far underneath the earth (like your cellar :) ) You then ...


4

The attack was made possible by an error of the coin owners (trusting the online wallet) and another error by the online wallet admins (they didn't make public the exact details, but the attacker certainly exploited a vulnerability that should not have been there). The same is possible for cash/gold etc: if you trust a safe-deposit box to hold an ounce of ...


4

Yes, the attack you describe is possible. But this isn't specific to blockchain.info nor to online wallets. If an attacker manages to run code on your machine, you're pwned. As long as an attacker manages to inject code which deals with the private keys in their unencrypted form, the attacker can make it send the keys back to her. One way an attacker can ...


4

The commit implementing the fix was issued Mar 14, 2017, 3:16 PM GMT. A Github release was made at 7:39 PM GMT. It was announced on Reddit at 7:59 PM GMT. The vulnerability was discovered sometime before the git commit, but it's unclear how long before. According to nodecounter, things were fine at about 6 PM GMT, when there were 776 nodes. That rapidly ...


4

You are not being hacked. These are not two separate transactions; it is one transaction with two outputs. The second output was automatically created by your wallet client and sends back to a new address which also belongs to you. This is a normal and necessary feature of how Bitcoin works, called "change". See How does change work in a bitcoin ...


3

Not only can you write such a program, you probably already have one. If you run the standard Bitcoin Core client, you will see that debug.log logs the IP addresses of every network node it communicates with. (It's irrelevant whether you use the client for mining or not - even non-mining nodes need to connect to peers, and could keep track of which peers ...


3

If there were a serious vulnerability at Cryptsy end affecting all users the accounts were flushed in no time, so I doubt this is an issue with Crypty itself. Otherwise there were already 1000 posts on Reddit regarding it. The malware targeting cryptocurrencies users is very, very, sophisticated due to high value of the users being targeted. Some real-life ...


3

I figured this out a while ago. Couple of weeks after I got hacked I noticed an unknown process in the task manager. After googling the name of the file that was linked to that process (I don't remember the file's name) I found out it was a trojan horse. Afterwards I deleted it, changed my passwords, and checked out from time to time for unfamiliar processes....


3

According to this speculative thread at bitcointalk.org forums, a minimum of 27,000 BTC (worth $370,000 USD at that time), with a possible maximum of 75,000 BTC, estimated. Here's a screen cap of the first post in the thread, in case the forum later disappears:


3

Does freshly installed bitcoin-core node have genesis block included in the installation? Yes. This fresh node contacts some peer for downloading blockchain. Can malicious peer give node wrong chain? Is this attack possible and how is it mitigated in bitcoin? There is no way for the chain to be "wrong" that would not be detectable to the node. If it's ...


2

There were 3 BTC paid on the "release" side, and 0.72 BTC paid on the "don't release" side. So it brought in under $50 USD worth. And the deadline passed with no tax returns. http://www.dailydot.com/news/blackmailers-50-dollars-bitcoin-romney-taxes/


2

Could you be more specific on which 2 way authentication you used? What where the exact steps so we can rebuild the scenario or at least understand what happened exactly. If it was email by gmail consider the machines you used the blockchain.info/ gmail on as compromised. Most probably all login forms on this machines have been grabbed.


2

You do not have a Bitcoin wallet at LocalBitcoins. Instead you have only a ledger account with their hosted (shared) Bitcoin E-Wallet. What this means is that you cannot use the blockchain to track your balance. You can only use it to determine how many confirmations your transfer (deposit) has received. The E-Wallet provider simply credits your ...


2

The two most likely scenarios are that you either had malware on your computer/phone that stole your private keys and was able to spend them on your behalf, Or you used easily guessable brain wallet seed. Brain wallets use easy to remember list of words or a phrase. The problem is that if it is not done correctly, then anybody can guess random phrases and ...


2

TX_1 is invalid because it is in conflict with the newly confirmed TX_5. TX_3 and TX_4 are also invalid because they depend on TX_1. TX_2 remains a valid transaction. However, if Mr. Hacker's double spend attack involved orphaning the single block in which TX_1 and TX_2 were both contained, then TX_2 no longer appears on the block chain and now has 0 ...


2

I had to diagram this out as the transactions and block chain might actually appear: Inputs/Prev Outpoints Outpoints TX1 A:0 TX1:0, TX1:1 TX2 B:0 TX2:0 TX3 TX1:0, TX2:0 ? TX4 TX1:1 ? TX5 A:0 TX5:0 (TX5) Block A ------> Block C ----> ...


2

Based on Andrey's 2^160 addresses, I did a thought experiment. Let's say Dr. Evil wants to occupy all the bitcoin addresses, because of something Satoshi once said about his ears. He thinks of using 1,000 evil computers for the task, but he's in a hurry and he's quite wealthy, so he buys 1 million evil computers instead. He sets each of those computers to ...


2

It is still possible to embed data into the blockchain, and it is actually fairly trivial. But don't do it. It is rude and detrimental to the network as it takes up resources to host your random data on all full nodes in the network. The polite way to do it is to create an OP_RETURN output, but that only allows up to 80 bytes of data. The impolite way is to ...


2

Yes, it's absolutely still possible; nothing has changed to prevent it. It's not clear how you even could if you wanted to; because of the consensus requirement, you would need some universally agreed, computer-testable standards as to what sort of data was unacceptable. Any such standard would surely be extremely easy to circumvent. Anyone can insert 80 ...


2

The chain would split and when the networks re-connected the longer chain would take precedence. All transactions on the orphaned chain from the time of the split would be invalidated. Good if you were a spender, bad if you were a receiver. Note that one company in particular has already deployed a satellite system that broadcasts bitcoin blocks. If there ...


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