Transaction "DDOS"

[BitcoinBug]

Hi there!

I've read as much as I could for the last day or two, but one question is still bugging me and I would like to get it answered before I invest money into this. And the question is:

how is bitcoin protected against transaction flood by anyone not liking the whole bitcoin philosophy, e.g. governments around the world, unable to collect taxes from it. As far as I know, most bitcoin clients have the whole transaction database loaded, which is currently about 700MB on my computer. This is a lot for an early phase project. Wide adoption could quickly generate gigabytes of transactions a year and malicious distributed attack could probably do it even faster. Since every client is meant (is it?) to have all transaction history it would soon become a resource hog and impractical for most desktop computers.

Thanks!

[chungy]

Easy: transaction fees.  Not much of a bother for legitimate individual transactions, big bother for DDoS.

Also, the database shouldn't grow that much per year.  Not sure why you have 700MB, mine's around 450MB (Linux; if it's bigger on other systems then I suppose I can see that).

edit: I've read there are also ways for clients to have a narrow block chain rather than the whole thing, which will be great for mobile clients.

[BitcoinBug]

So it is a NO for DDOS, but what about legitimate uses? If current userbase generated 450MB , how much would 100x userbase generate a year? Tens of gigabytes?

[caveden]

There are 2 issues there. One is abusing the disk space of miners by making the block chain grow to much. Transactions fees prevent this.

Another is sending tons of microtransactions to yourself in order to consume the entire bandwidth of all bitcoin clients. This can be avoided by refusing to propagate the transactions of a peer which seems to be flooding. But currently the mechanism used is that transactions which don't obey a hardcoded transaction fee policy are not propagated by the default client software. I don't like this mechanism very much, I hope one day it gets replaced by something that doesn't impose a transaction fee policy. But it's better than nothing anyway.

[caveden]

So it is a NO for DDOS, but what about legitimate uses? If current userbase generated 450MB , how much would 100x userbase generate a year? Tens of gigabytes?

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

[BitcoinBug]

So it is a NO for DDOS, but what about legitimate uses? If current userbase generated 450MB , how much would 100x userbase generate a year? Tens of gigabytes?

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

Thanks!