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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

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 ...


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

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.


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 ...


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

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

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

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 ...


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

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 ...


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

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 ...


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

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

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

IP addresses are not private information. As for email and name no one can get that information based on the blockchain data alone unless you go out of your way to publicly associate your identity with a specific address. For example by mentioning your email, name and address together on some website. Another possibility is that you reveal your identity to ...


2

Block verifiers don't manipulate the block chain. What matters is the economical weight of those verifiers, not the number of node processes they run.


2

Each Bitcoin transaction is signed using the private key(s) of the sender(s). The cryptographic signatures both provide authorization of the payments and ensure integrity of the transaction. The signatures commit to a digest of the transaction, which means that the signatures are invalid out of the context of exactly that transaction, even if the transaction ...


1

Is there any relationship to each address? Like based on seedphase? or Just literally making 'random' address? It depends. In old versions of Bitcoin Core, addresses were just randomly generated and the private keys stored in wallet.dat. Newer wallets that implement BIP32 derive all of the wallet private keys from one master private key. If so, an ...


1

Can hackers behind the ransomware WannaCry be traced through bitcoin transactions? no, if they are smart enough Is there is central server of bitcoin no where all transactions can be looked up from? yes And is it possible to identify hackers from IP address used to access their bitcoin accounts? no


1

Edit: Blockchain.info is open source, the algorithm is public. The mnemonic that they use stores information about your wallet id and your password only. Previous answer: You should read into BIP 39 this covers how mnemonics map to the values that are used to create a HD wallet the algorithm is very well known and corresponds to the size of the key space ...


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