Bitcoin Forum

At first I thought it would be worse but I'm not sure anymore. Maybe CoinHunter is right but I'd like to hear the opinion of some other technical people.

This is the only discussion I've found so far in the subject: https://bitcointalk.org/index.php?topic=31587.0

Before anyone chimes in with a "easier to double spend due to lower difficulty" argument, I'd like to restate that the shorter block time disadvantages the attacker. With bitcoin, they have more time to produce their blocks because the rest of the network is also on the higher difficulty. The network latency is the only real issue with this, causing more chain splits (with those come easier double spending, but require precise timing).

here is a discussion about solidcoin with the founder defending (https://bitcointalk.org/index.php?topic=38851.0)

it's not about security, though.

Here in the faq they say 10 minutes was picked for a reason... (http://Why ten minutes specifically? It is a tradeoff chosen by Satoshi between propagation time of new blocks in large networks and the amount of work wasted due to chain splits. If that made no sense to you, don't worry. Reading the technical paper should make things cleare)



however reading the paper, it doesnt seem to go into the "amount of time wasted due to chain splits"

it does suggest that the more blocks an attack falls behind the hard it is for him to double spend and suggests that once he has the computational power to double spend, he would more likely find it more profitable to just legally mine.

I'm not totally sure one way or the other, as seeing the i0coin release and its chaos with the chains, I'd have to believe there is a limit based on time wasted due to chain splits, but I would have to guess that this limit is a lot less than 10 minutes.

Someone did offer a bounty for a double spending attack, but as far as I know it has not been collected.

Computing power is wasted every time a fork appears.
And what's the alleged advantage? Faster transactions?
Well, yes, but not as secure as 10 minutes blocks. With the same computing power, a 10min block will be twice as secure as a 5min block. You're not more protected against double spending with 2 5mins blocks than with one 10 min block.
Also, we don't want faster transactions, we want real time transactions, and that cannot happen within the block chain. Other means are needed, for example, the green addresses technique.
I don't think 5min blocks are a good idea.

There is absolutely no reason that longer block times would increase security though. If that was true, than you could argue that one 60 minute block is just as secure as 6 10 minute blocks. This is not the reason shorter block times are bad, as consider this example:

I have so much of the network hashing power that on a ten-minute block system, say Ten-coin, I have a 1% chance of producing a block in one minute. Therefore the amount of produced blocks in ten minutes on average is 0.1, and the rest of the network produces 0.9.

I switch over to a five-minute block system with equal hashing power. I now have approx. 2% chance of producing a block in one minute. Therefore the amount of produced blocks in five minutes on average is 0.1, and the rest of the network produces 0.9.

Since double-spends require more than one block in a row, and you have the same share of blocks in a five-minute system, the chance of more than one block in a row is the same or marginally increased.