Bitcoin Forum

What is the technical reason i cannot listen for new txns, modify them to spend to my address and rebroadcast as my own?

Txns are not encrypted, the target public address is visible and I can modify it and rebroadcast. What am I missing?

You're missing signatures (https://en.wikipedia.org/wiki/Digital_signature).

From what I know from testing and reading for some weeks with blockchain-spec and reference client: If I'm an attacker with the intention of cheating for coins I'm going to look in to forking and mining delayed blocks..

And to make one of them you need private keys.

is this really happen?what do you think about algorithm?what algorithm they use?

If you have enough money for this kind of attack you maybe can rollback/invalidate transactions but you are not able grab the coins from these transactions.

All transactions, as previously mentioned, are encrypted with digital keys. You would have to be an excellent programmer to break the encryption.

They are not encrypted. They are signed, which means that if any data in that is signed changes, the signature won't match.

But encryption and signature are pretty much the same thing, right?

No! Encryption is converting a plaintext data to ciphertext so that only a certain persons can know what the plaintext is. Signing requires that the message ( plaintext) is known. It proves that the data was not modified.

To encrypt the lost Bitcoin details is very hard dude. and he would get his Bitcoin from the hackers If he feels pity only. If he is a good person He could get from him. he willingly he hacked means you can't get your hard earnings back for sure

hacking bitcoin transaction can be possible,as i read before that last year, Hacking Team already mentioned that they’re working on a feature that could expose transactions related to bitcoin and other cryptocurrencies. Documents have shown that this feature can also expose transactions using litecoin, feathercoin, and namecoin.

source?

You are missing everything. Bitcoins work on a different security algorithm, simply modifying transactions and sending bitcoins to your address will never happen.
Wallet providers are not idiots, they use multi layered security and these methods won't work for it. I don't know the actual method, as I'm not interested in doing hacking. But, whatever it is.. It is complicated.

It is not just the wallet, it is built into the bitcoin protocol itself.

If I am understanding the correctly, all of the information in the BTC programming is needed in order for the block chain to properly work right.  So I am guessing in order for you to do that, you would have to rewrite the complete block chain from the start so it all lines up.  Am I on the right track with my thinking?

No, "rewriting" the blockchain will not enable you to forge a signature. You either have to break ECDSA (or the specific curve used for bitcoin) or get the private key in question. Also not every single line of code within bitcoin core is needed for the protocoll to work. A large portion is the wallet part that is not required.

Forget about gaining Bitcoin quick and dirty way by hacking, it's not possible. Every part of the Bitcoin security practices was carefully reviewed by the world's greatest security experts, and there are no holes in them. This doesn't mean you shouldn't take your time to learn as much as you can about Bitcoin code, because you can actually get money from that by offering your programming services to others once you figure out what exactly is going on there.

Rewriting the blockchain is impossible for anything but the most recent blocks, and rewriting those would need over 50% of the computational power of the entire network. Each block in the blockchain contains a hash of the previous block in its header. If you attempt to change anything in the previous block its hash changes, and the next block needs to store that changed hash in its header. All Bitcoin nodes store a copy of the blockchain containing those hashes, and if you attempted changing an old block they would refuse to accept it as valid because its hash wouldn't match theirs.

1. there is nothing encrypted.

2. in user wallet there is a hidden secret "private key" only the true owner of coin can sign "spend" his coin.

3. singature becomes invalid when you change anything in the transaction.
    - you cannot change the amount
    - you cannot change the destination

3. the obstacle to "fake" this signature is
 -  you do not know the key: solution: steal the wallet
  - you cannot fake ECDSA signature: solution: hack ECDSA
  - you cannot change payment: solution: find a SHA collision or RIPEMD collision

currently
ECDSA has not been hacked (nobody knows how to do it)
SHA collision has not been found (nobody knows how to find it)
RIPEMD collision has not been found (nobody knows how to find it)

Do not understand it much, I am not hi-tech into bitcoin... but it is likely that your hacked transaction would not be the one accepted because other nodes will get the transaction and confirm it before you?

No, the reason is:


You can "hack" (as in change) the transaction all you want. If you want the coins to go elsewhere you either need the private key (so the coins are yours anyway) or the signature will be invalid and the transaction not accepted.

Yeah they can try to break, But Bitcoin protocol uses combination of 2 of the strongest non-classified algorithms used by the NSA for encrypting Secret level documents and Breaking the signing algorithm requires a selective forgery attack or stronger and means that arbitrary transactions may be forged and entered into the system.

I'm sure it's not possible and its best for everyone that it never is.  Bitcoin hack would be catastrophic.

I've read somewhere it might be possible to hide blocks that you can mine before they are broadcasted too. I forget the specs to the theory but it probably required controlling a peer or something to do with forks or fee-delays.

Would controlling a mass node (by that I mean like all the nodes on blockchain) mean that you could perchance have the ability to control the whole blockchain?

They aren't encrypted, but you can't broadcast them as your own. You're missing the tx signature. You also need all the other miners to confirm you transaction. You know how hard it is to change a transaction with even one transaction?