What I would like to see is lower time to get started – currently, it takes several hours just to download all the blocks, which amount to few megabytes of data.
Or does it take so long because my PC has to verify all the blocks?
You've made me think of another question to ask: will all new instances of BitCoin clients always have to download all existing blocks? Won't that eventually mean that as the number of blocks increases, the time taken to download the blocks and the space to store it will be enormous.
I'm presuming I've got this wrong, as the developpers are rather cleverer than me, but can someone explain the flaw in my thinking?
If I am correct, Bitcoin *can* work with only the last block. If I'm not, correct me!
But this is insecure because if that last block isn't verified, it might be bogus!
Every block is signed with the previous block. (Or something like that. I'm not an expert on the algorithm.)
So, if you don't have block 10, you can't verify if 11 is valid, you first need 10 for that, and to verify 10, you need 9, and so on.
When Bitcoin starts, it begins downloading the genesis block, and verifying it, and continues down the line checking all blocks and saving them. It's like a linked chain!
Eventually every block in existence has been checked and saved, and right now that's like 27 megabytes.
The block downloading mechanism isn't that fast. If I am correct it writes the whole file to the harddrive everytime -- or maybe just one sector -- when it gets a new block, so it'll write 65000 times to your hard drive... not exactly what you call 'nice'.
I have a solution.
Anyhow, does Bitcoin need all the blocks to function? Yes
Can we hardcode a block into Bitcoin to save time? Sorta, we don't want to download just from that hardcoded block on. Not saving every block makes the network insecure and starts a dependence on older clients which have saved all the blocks!
So we cant
save space? No, not by not saving the blocks, that's insecure. We can hardcode a block into Bitcoin, and initially let Bitcoin not download from the genesis block up to the hardcoded block.
Bitcoin will then download only from the hardcoded block up to the current block, and after that the client can be used. (To generate/transfer coins/etc)
So we have a he chain up until the verified block, we make the network insecure and start a dependence on the older clients which have saved all the blocks!
By asking for that same block, and verifying it's local hardcoded copy, the client can just skip downloading the first blocks up to the hardcoded block temporarily
Then after those blocks have been downloaded, and ofcourse, verified from the hardcoded block on, Bitcoin will start downloading from the genesis block up to the hardcoded block and verify those.
Thus enabling Bitcoin to be used without waiting that long, yet still preserving the genesis block up until the hardcoded block.
And when the network grows larger, we can just move the hardcoded block to the current block when the release is compiled.
This seems to me like a great solution to the problem of having to wait a long time.
This might be insecure, but only so far.
The hardcoded block's data will be hardcoded and compared against the received block.