Answer of cryptopia
"Thank you for contacting Cryptopia Support.
Our recent Aurum Coin investigations have concluded that the AU network was victim to a 51% attack. We are in contact with the AU team and are trying to reconcile the resulting issues, will provide further updates in the near future.
We appreciate your patience while we work to resolve the resulting issues.
Kind regards,
Olivia"
Lafu are you from cryptopia at all?
Lafu is a volunteer chat moderator for Cryptopia.
He is correct. Cryptopia did not get hacked. The Aurum coin network had a 51% attack. This happens when an attacker has more hashrate than the coin network and the attacker uses this to exploit the coin network.
The network nodes confirm that transactions have taken place but the attacker replaces this part of the chain with their privately mined chain which causes it to reject the previously confirmed transaction - resulting in "reversed transactions" and lots of orphan blocks.
I explained it here:
https://bitcointalk.org/index.php?topic=5035336.0It has happened to a number of POW coin networks recently. It occurs when the coin network maintains insufficient network hashrate to protect against such an attack. The attacker didn't "hack" the coin network. Instead they
exploited the low Aurum coin network hashrate and effectively
took over the Aurum blockchain during the attack.
The attacker controlled over 51% of the hashrate which over-ruled the legitimate publicly mined transactions by the honest miners.
Coin networks can avoid this by ensuring algorithm and reward parameters such to entice sufficient hashrate. They can also implement checkpointing and other technological countermeasures.
When a coin network falls victim to a 51% attack it is neither immutable nor decentralized.
The most notorious recent 51% attack was the one on the bitcoin gold network which resulted in Bitcoin Gold being delisted from Bittrex.
Cryptopia also have an explanation in their knowledge base:
https://supportcryptopia.service-now.com/csm?id=kb_article&sys_id=91fc54cddbfc2b0052d2ef728a961948https://i.imgur.com/p3EprSQ.pnghttps://archive.fo/6BNAwCoins listed on Cryptopia have ongoing obligations to remain listed outlined here:
https://support.cryptopia.co.nz/csm?id=kb_article&sys_id=5d7482d2db9e9bc032a664a14a96199fIt includes:
You need to give us notice of the following:
Major issues with your coin, including hacks or network problems, as soon as you become aware of them.
Is your protocol and consensus mechanism secure? We may decline coins we think are vulnerable to 51% attacks.
Be aware of our delisting policy and your ongoing obligations:
Cryptopia reserves the right to remove any coin listed in its exchange markets for violations of our listing terms. This is solely at our discretion. Reasons a coin may be eligible for delisting include, but are not limited to:
Any network issues or vulnerabilities that could be exploited. Examples include:
Low hash-rate.
Reason to delist:
https://support.cryptopia.co.nz/csm?id=kb_article&sys_id=b8aa010ddb452b80d7e096888a961934The following criteria are required to be met by coin projects at the time of the listing:
Active and visible development team with at least two contacts given to Cryptopia (Lead Developer and CEO or Marketing Representative).
Below is a list of factors that are being constantly reviewed by our Cryptopia Service Delivery Team that may result in a token/ coin being delisted:
The token/ coin no longer meets our listing criteria.
A loss of, or poor communication between coin teams and our Cryptopia Listing Team.
Project is abandoned, *e.g.: No visible coin team, no working block explorer, no active updates on code repo, or no working website.
The token's/ coin's blockchain becomes compromised or there exists a possibility to be compromised based on hash rate, namely a 51% attack.
