Smart Science: How does Filecoin prevent witch attacks?

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Sybil Attacks is one of the three network attacks faced by Filecoin. It means that malicious nodes cheat the network by cloning IDs to obtain additional benefits. This method is called a Sybil Attack. So, where does the name of this Sybil Attack come from?

The film, based on Flora Rhea Schreiberie's 1973 novel The Witches, is about the psychotherapy of a woman named Sybil Dorsett, who was diagnosed with dissociative identity disorder and had 16 personalities.

Similarly, if there is a malicious node in the network, the same malicious node can have multiple identities, just like the 16 identities split out by the heroine in the movie. The data that originally needed to be backed up to multiple nodes was deceived and backed up to the same malicious node. For example, the malicious node disguised itself as multiple identities. This is a witch attack.

This type of cyber attack is as scary as a witch

In simple terms: a user submits a network request to store N independent backups. At this time, a malicious node generates Y identity identifiers, and the network thinks that there are Y independent storage nodes, while the actual storage score of the malicious node is less than N or even only one.

However, the malicious node may obtain N independent backups (rewards). In other words, it may obtain N times the block FIL coin reward. At this time, the malicious node attack is successful.

So how does Filecoin solve the Sybil attack?

First of all, everyone should understand why Filecoin needs to prevent witch attacks?

It's very simple. For example, a manufacturer only has one node for Filecoin mining, and then it uses a witch attack to enable 10 nodes to mine Filecoin at the same time. However, the manufacturer only contributed the storage computing power of one node. It is as if it only did one job but claimed 10 rewards. This situation deceives the Filecoin official and the Filecoin network.

Therefore, in order to prevent fraud and ensure fairness, the Sybil attack problem must be solved.

Replication proof is Filecoin's solution to prevent Sybil attacks. The core idea of ​​replication proof is to ensure that the prover saves an independent backup. So, how is replication proof implemented?

The first step is to make the encryption time long and the decryption time short. By extending the encryption time, malicious miners cannot challenge by temporarily generating encrypted files in time, because generating a copy proof requires the prover to use the encrypted file as input, which means that only when the miner actually stores the encrypted file can the challenge be completed on time. Shortening the decryption time is to extract files faster and reduce the loss of computing resources.

The second step is to submit storage proofs regularly. Miners need to submit storage proofs at regular intervals, which means they need to submit proofs to the Filecoin network for inspection and verification on a regular basis. Because the encryption process takes a very long time, it is necessary to reduce the length of the challenge time, decryption time, and verification time, that is, to reduce the complexity of generating storage proofs.

The entire process above is Filecoin's Proof of Replication (PoRep) .

The basic definition of PoRep is this: the verifier V provides a unique data proof π to the prover P to convince P that he stores a specific backup Di of the data D. This proof is a response to the challenge C generated specifically for P.

The common understanding is this: a miner named Liu Da (validator V) said to a user named Xiao Zhang (Xiao Zhang has published multiple storage tasks to the network), "I have a unique data proof in my hand, which is a backup of the storage task you published, and there is only one copy of this backup."

As long as the two people's "secret code proofs" match, and as long as user Xiao Zhang confirms that there is no problem, miner Da Liu can get the corresponding backup task bonus (Filecoin network challenge to explode blocks and issue coins).

No, at the beginning of the year, the Filecoin network was still unstable, and even during the test network, a system bug occurred, and some node miners maliciously obtained a lot of virtual FIL coins. So, do you understand why the Filecoin network needs to be tested?

This is to ensure the stability of the system after the official mainnet is launched. Otherwise, if problems or loopholes occur after the mainnet is launched, it will not only be unfair to other miners, but may also have a very serious impact on the entire Filecoin network ecosystem.

The reason why Filecoin officials set aside 4.25 million FIL coins as rewards to stimulate miners to participate in the test network and calibration network is to use the code after the main network is launched as a real simulation to see if any problems will arise.

The Filecoin Space Race is about to begin on August 25 and is now in a 24-hour countdown. I believe that major manufacturers have begun to gear up. After all, this is a competition to share the grand prize and prove strength, which concerns the future survival of many manufacturers and the market structure of the Filecoin mining circle.