Re: Dealing with SHA-256 Collisions

[aaaxn]

True - but the likelihood is *why* the answer is not relevant (i.e. in "fairyland" we can have such a blockchain but in the real world we cannot).

Seriously if you want to *worry* about something then worry that the banks invent Bankcoin (which may or may not just be a bitcoin clone) and spend say 1 billion USD promoting it (nothing to them) wiping out all value for BTC after governments all decide that its usage should be banned.

I'll take that for yes. Not need to include you worries.
Anyway if I wanted to worry bitcoin have enough serious economic problems so I don't need technical ones

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[Kazimir]

Instead of the double hashing that Bitcoin currently uses, i.e. sha256(sha256(x)), I would have preferred a nested double hash, i.e. sha256(sha256(x)+x) where '+' means binary concatenation. For one, this avoids entropy reduction. Which normal double hashing does not - the 1st way can (and most likely will) have less effective entropy than the 2nd.

Or ever better, the recursive hashing depth could increase with every N blocks. So after a specific (considerably large) number of blocks, the hashing method would become: sha256(sha256(sha256(x)+x)+x), etc.

Anyway, even with the current simplistic double hashing, if sha256 ever gets broken (not to be expected in the forseeable future), Bitcoin is still safe for a *long* time and we have plenty of opportunity to switch to sha512 or sha3 (keccak).

[jdbtracker]

Definitely in our future, Bitcoin clones popping up everywhere! That is a more pressing concern than worrying that the encryption will be broken in the next 40 years.

I don't mind some of them, like CureCoin or ScienceCoin, those sound like interesting proposals with serious bandwidth problems if they try to use Bitcoin's system... I like them.

Bank coin, hmmm does that mean they call the stakes and our collective evolution of Bitcoin will be grinded to a halt?
This is BankCoin! This is how it is! do as we say not as we do!


Binary concatenation seems quite effective, definitely limits the problem of duplicate hashes, but what about the bandwidth needed? would it increase the size of transactions? Is the limit 500kb/block right now?