Ok, I get what you are saying.

This would require bitcoin to first examine the entire blockchain to make sure that all hashes are indeed valid and correct, and that all work was done.

However this does present a problem for the future: the idea was to "cut away the blockchain" and replace it with a hash only, this is the concept of the merkle tree.

Perhaps this is not yet done to make sure the blockchain is long, but after a certain while this long blockchain might become impractical and will have to be "pruned/cut away" leaving just a hash.

At that point it will become easier since there is no more blockchain to check it has been pruned away, leaving only the remaining blockchain to be checked.

Impossible is a dangerous statement to make, but I will accept it for now, but the impossibility will surely go down as computers become much more powerfull.

All processing power in the world today, might be in somebody's pocket in 10 years or so... perhaps the difficult will have risen or perhaps not, see my question about maximum difficulty.

So bottom line:

1. Large parts of processing power might be ignored because of merkle tree hash pruning.

2. Large parts of processing power might be easily reproducible because of super computers in the future.

3. Leaving only recent work done, which leads to the question of "maximum difficulty".

If maximum difficulty is achieved in 1 second times, then perhaps switching to a different hashing technique might be possible to increase it... so this probably answers my own question about difficulty.

However getting the whole world to switch to a new standard is difficult as ipv4 to ipv6 has proven to be


Considering your point 2: miners can do empty transactions, is this actually done in practice to work when there is nothing real to work on ?

I found some partially answers to parts of my questions on this wikipedia link:

https://en.bitcoin.it/wiki/Weaknesses

Which I will quote here:

"
Every few releases of Bitcoin, a recent block hash is hardcoded into the source code. Any blocks before that point can't be changed. An attacker starting at that point would have to reduce the difficulty, but this would require him to generate blocks at a much slower rate than once per 10 minutes. By the time he finally gets to a difficulty of 1, a new version of Bitcoin with an updated hardcoded block will probably have been released.

"Block chain length" is calculated from the combined difficulty of all the blocks, not just the number of blocks in the chain. The one that represents the most CPU usage will win.
"

My thoughts on it:

The hardcoded block hash, assuming it is just a hash, offers some protection, but not absolute protection, a block hash collision might still be found by an attacker, which could still allow him to change the history of the blockchain.

This is pretty much the same thing as "bitcoin mining" where a hash needs to be find with zeros in it, except this time, the entire hash must match.

So it can probably be considered "maximum difficulty" for the attacker.

Which is a good question: Is there such a thing as "maximum difficulty" ?

If not, how is maximum difficulty extended to infinity ?

If no, then bitcoin might fail in the future when maximum difficulty is easily processed.

(Let's call this: "Super computer in your pocket which does maximum difficulty attack in 1 second " )

The block chain length is kinda interesting, this requires the attacker to examine the real blockchain, and make sure his fake blockhain is longer...

Hello,

I have some questions about bitcoin addresses, which are used to transfer money from/to (wallet?):

1. What exactly is a bitcoin address, without having to look at source code, what is the concept behind it ? Does it perhaps hash my ip address as part of the calculation of generating a new one ?

2. How does bitcoin prevent multiple people/persons/clients/computers from accidently generating the same bitcoin address ? (Perhaps it's checked against transactions in the blockchain to scout for duplicates ? But this does not protect against transactions already underway but not yet in the blockchain...)

3. I read somewhere that after receiving bitcoin into my wallet, a new address would be generated to improve privacy/stay anonymous... is this indeed true ? This would be a little bit problematic for people wanting to sell a lot of products to different people ?!? Because each time their receiving address would change ?!? (I guess some software for merchants/product sellers would need to be created which automatically updates these addresses so people can transfer money correctly... ?!?)

Bye,
  Skybuck.

Hello,

I have some questions about potential weaknesses in the blockchain idea and how bitcoin potentially solves it ?

First question:

1. Suppose the attackers manage to outrun the defenders with a blockchain of +1 for the attackers.

Are the attackers capable of replacing the entire blockchain with bullshit transactions ?

If not how does bitcoin protect against replacing/invalidating the entire blockchain ? (Perhaps it uses some kind of timestamp/datestamping to prevent this from happening ? For example after X days the transactions/blockchain cannot be replaced ?)

2. How does bitcoin protect against the "no work to do" situation ? For example: there are no transactions being broadcasted, miners have no work to do. But an attacker could make a bullshit transaction and start working on the next block, while the miners have nothing to do... (More or less related to question 1 as well).

Bye,
  Skybuck.