this post was submitted on 19 Jun 2026
94 points (91.2% liked)
Asklemmy
54666 readers
986 users here now
A loosely moderated place to ask open-ended questions
If your post meets the following criteria, it's welcome here!
- Open-ended question
- Not offensive: at this point, we do not have the bandwidth to moderate overtly political discussions. Assume best intent and be excellent to each other.
- Not regarding using or support for Lemmy: context, see the list of support communities and tools for finding communities below
- Not ad nauseam inducing: please make sure it is a question that would be new to most members
- An actual topic of discussion
Looking for support?
Looking for a community?
- Lemmyverse: community search
- sub.rehab: maps old subreddits to fediverse options, marks official as such
- !lemmy411@lemmy.ca: a community for finding communities
~Icon~ ~by~ ~@Double_A@discuss.tchncs.de~
founded 7 years ago
MODERATORS
you are viewing a single comment's thread
view the rest of the comments
view the rest of the comments
Is it rewritable, or is it append only? You only wrote one sentence yet still managed to contradict yourself so I suspect you have a very meager comprehension of the technology.
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.
Go ahead and prove me wrong. Show me blockchain implementations that are immutable post append. On my end, we can talk about Bitcoin forks. We can also talk about the current state of consensus mechanisms, each of which has the explicit ability for large actors to rewrite history in their favor. Even Monero is susceptible because this is fundamental to the blockchain in any form. It’s been a huge reason why I make sure I get paid up front for any consulting I do in this space.
Only the last few blocks are "rewritable," which is why a certain number of confirmations are a necessity. Going any further back than that, would be a completely different chain - a fork. The last of of those occurring on Bitcoin was thirteen years ago when it was still encountering growing pains due to an uptake in usage. Forks of more than a couple transactions are not a frequent, regular occurrence by any exaggeration, so for all intents and purposes of modern crypto usage,, it is immutable, not rewritable.
If any of it is rewritable, none of it is immutable. You can’t have it both ways.
Notice I put quotes around rewritable. That's because it's not the correct term, and I was being charitable in engaging in your straw man argument. It's actually a collision of timing, where two solutions are presented for the same block in a short amount of time, and until the consensus is reached by the majority, both are temporarily valid. Once consensus is reached, it's final. There's no going back. In that sense it is not rewritable, it is immutable. It's just fuzzy for the first fifteen minutes which branch will resolve as the actual Blockchain in the event of near ties.
I don’t think you’re using straw man correctly.
You’re naively referring to how consensus should work while completely ignoring both the well-defined attacks I referenced and the reality of large actors in a consensus network. You don’t know what you’re talking about or you don’t understand how the theory works or you’re possibly just being obtuse. No matter what, this is pointless. Good luck.