Blockchain : Just going to post this here because the Nexus subreddit is using censorship to keep the truth from being told to their investors. They are misleading the community about their projects qualities.
I am doing some research on the topic of quantum resistant blockchain projects. Nexus claims to be quantum resistant, so I got to their subreddit and had a conversation with their moderators. I came to the conclusion Nexus is not quantum resistant at this point of time, while they claim to be the first truly quantum-resistant blockchain. The discussion became an argument and my comments on their subreddit where I explain how they are not quantum resistant, are deleted or removed. Now I seemed to be banned or blocked there. They keep a tight censorship on the subject. They remove and delete posts they don’t like to be seen.
Their claim to be quantum resistant:
From the website:
“Nexus is the first truly quantum-resistant blockchain, incorporating advanced cryptography designed to negate the threat posed by quantum technology of the future.”
Nexus “combines 571-bit private keys, 1024-bit Skein and Keccak quantum-resistant hashing algorithms, and an evolving signature scheme called signature chains. Signature chains update the private and public keys that secure your address and obscures them after each and every transaction”
This doesn’t make Nexus quantum secure though:
– Elliptic curve signature scheme cryptography as nexus uses, even 571-bit private keys, are known to be broken with a large enough quantum computer using Shor’s algorithm. So the keypairs used by Nexus are not quantum resistant. Meaning: if you would have a quantum computer, and the public key, you could derive the private key, and sign transactions of your own.
– Skein and Keccak are Hashing algorithms and useful to hash the on-chain public key. So they use the same method as BTC here, where the public key is only visible in hashed form as long as no transaction is made. Where, as long as no transaction is made, the public key stays safe from quantum attacks. But as soon as a transaction is made, these hashing functions are useless for protection, because while sending the transaction to the nodes, and during the transaction, the public key will be made public in it’s original form.
– The signature chains are pointless, because the vulnerable point is before the transaction is fulfilled. So the fact that you update the keypairs after a transaction is futile.
– Also the idea that there would only be a 1 minute window (The time it takes to include the transaction to the chain after the network starts process the transaction) to do the attack is not true. The attack will be done before the transaction is admitted to the network. Network based attacks, like specialized forms of Eclipse attacks, DDoS attacks, BGP routing attacks, NSA Quantum Insert attacks could create a much bigger window to create an attack and at the same time make sure the forged transaction will be admitted to the network before the original will be. The biggest threat will be MITM attacks though. No network modification would be able to prevent that, besides the use of quantum resistant keypairs.
To summarize why they are not quantum resistant:
Nexus uses 571-bit private keys which can be broken by quantum computers when they reach critical level. These keys can be hijacked when a transaction is sent from the users device to the blockchain network using a MITM attack. These attacks make it possible to 1) retrieve the original public key that is included in the transaction message. 2) Stop or delay the transaction message to arrive at the blockchain network.
So, using a quantum computer, you could hijack transactions and create forged transactions, which you then send to the nodes to be confirmed before the nodes even receive the original transaction. There is nothing you could change to the Nexus network to prevent this. The only thing they can do is implement a quantum resistant signature scheme. They plan to do this in the future, like any other serious blockchain project. Yet Nexus is the only of these future quantum resistant projects to prematurely claim to be quantum resistant.
Using the term “truly quantum resistant” is highly misleading. “Quantum resistant” is only used to describe networks and cryptography that is secure against an attack by a quantum computer in the sense that there is no algorithm known that makes it possible for a quantum computer to break that cryptography, in the way it is implemented, without any backdoors. They really should not advertise this way. It’s a misrepresentation of the truth to attract extra attention and investors. Being informed about this and then preventing this info from being public by removing and deleting comments is just scammy.
What is the Blockchain?
A block chain is a transaction database shared by all nodes participating in a system based on the Bitcoin protocol. A full copy of a currency’s block chain contains every transaction ever executed in the currency. With this information, one can find out how much value belonged to each address at any point in history.
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