I was specifically talking about drivechains being insecure.
I understand that there are two threats: an increased incentive for double-spending 51% attacks (stealing sidechain funds) and inflation attacks on the sidechain.
But isn't
this comment true, that the 51% attack, to create an invalid sidechain withdrawal to the main chain would need a fake chain of thousands of blocks (13,150 to be precise) and thus, a really big and stable cartel of miners to be achieved?
And regarding inflation attacks: I meant to have understood Paul Sztorc addressed such "on-sidechain" attacks and thinks they are not a threat to the main chain because they should only affect weak sidechains which are not "worthy" to be saved. Their peg simply would fail and they would die (or become a non-pegged "standard altcoin").
See here for his argumentation. Main chain would not be affected; for main chain a withdrawal "to the sidechain" is like a normal transaction.
Particularly, I'm referring to this argument:
In other words, if a particular sidechain is holding Bitcoin’s exchange rate down, we would HOPE that miners steal from it, and quickly! In the same way that we would hope oncologists would assassinate our cancer cells; or that poorly-run businesses will fall apart and free up capital for better entrepreneurs.
The only threat I can understand from my layman's perspective is that a failing sidechain could lead, psychologically, to the belief that "Bitcoin" has failed and thus create market convulsions.
Anyway, I would like to see Drivechains first to be implemented in some altcoin - this would even help because then we very likely _will_ see
failing and weak sidechains and the effect they could have on the main chain and its security.
There is also a second option: a "pegged coin" in the style of BitShares or DAI (which may be what Carlton Banks wrote about), over-collateralized by another "base" token to be used as a sidechain for BTC (well, it already exists with BitBTC, albeit with a semi-centralized base layer). However, this would have as a consequence the existence of strong altcoins serving as a base for these "peggedchains", and thus would not necessarily boost Bitcoin's dominance. (I'm however convinced that a BTC monopoly is impossible, even if we wanted it, because incentives to run altcoins are too strong.)