So in Bitcoin (or its many alts), as I understand, a bad actor can spend a fortune (or not) to try and 51% attack the network by gradually re-orging the chain by marching back the blockchain in time, block by block i.e a sustained a persistent attack is required.
Since Grin dispenses with the model of a huge blockchain which (unnecessarily) records every UTXO spend, what are the implications of a 51% attack on Grin? Is it easier to re-org its chain since there is less “time” (blockchain history) to rewind?
Mimblewimble is more about how chain is structured and has little to do with the consensus part. Consensus is the mechanism that keeps blocks in order and both Bitcoin and Grin run on PoW. Recreating blocks on an interval (a, b) depends (roughly) on the cumulative energy used to produce the blocks on that interval. Bitcoin miners use far more energy on a 1 minute interval than Grin so the Bitcoin network is more resilient to 51% attacks. It all depends on how much energy is put into mining.
While Grin doesn’t record (historical) spent utxos, it still records tx kernels. Since a doublespend attack requires re-orging an entire tx, not only the spent utxos but also its kernel, there really is no difference with Bitcoin.
% 51 attack is more social governance failure, those spent utxo kernel stuff is noise.
It is a failure of blockchain social and economic governance model. The market cap of the coin is low, so the cost of renting hashpower to attack it cheaper.
A sociopolitic reality of broken promises and incompetence.
