As I understand, it’s normally append-only. But, with some implementations, if a malicious entity controls most of the block production, they can undo recent transactions at will.
Some resort to majority vote, in the case of disagreements. Theoretically, if someone owned/controlled over 50% of the database, they could rewrite it, and have their version seen as true.
For the few valid uses of it, that shouldn’t be a problem. It will also be reasonably detectable beforehand.
It’s not as simple as that. Each block solves the problem of the former block, so to change something five blocks back, you now need to solve six blocks prior to writing the next block, otherwise it’s not cryptographically valid. The resources required to accomplish that are not trivial, and it’s never been done. Very theoretical indeed, in the same sense you could theoretically run through a wall if all of your atoms missed all of the atoms in the wall when you should have collided.
As I understand, it’s normally append-only. But, with some implementations, if a malicious entity controls most of the block production, they can undo recent transactions at will.
Some resort to majority vote, in the case of disagreements. Theoretically, if someone owned/controlled over 50% of the database, they could rewrite it, and have their version seen as true.
For the few valid uses of it, that shouldn’t be a problem. It will also be reasonably detectable beforehand.
It’s not as simple as that. Each block solves the problem of the former block, so to change something five blocks back, you now need to solve six blocks prior to writing the next block, otherwise it’s not cryptographically valid. The resources required to accomplish that are not trivial, and it’s never been done. Very theoretical indeed, in the same sense you could theoretically run through a wall if all of your atoms missed all of the atoms in the wall when you should have collided.