Checkpoints mechanism

Problem

PoS/BFT blockchains are vulnerable to so-called long-range attack

Its essence is that when you start synchronizing your node with the current state of the blockchain, you have to start checking blocks 0,1,2,... and so on. At the same time, you need to take these blocks from somewhere and here is the problem - how to make sure which block is valid?

If, say, block 1337th was generated and confirmed by the network more than 3 years ago, then with a high degree of probability those old validators are no longer active and may have even removed their shares from staking. A problem arises - you cannot clearly determine which block with index 1337 was correct - anyone can offer you any valid fork.

What are hostchains ?

Hostchains are independent L0-L1 blockchains that rely on their own security, fault tolerance and decentralization.

We use their TOTAL POWER as the maximum source of liquidity and decentralization

Solution

In order for you to be able to check the relevance of your copy of the blockchain, the current quorum (current validators who have frozen their stake and who can be trusted because they have something to risk) makes "checkpoints" to other blockchains once per epoch (or with other frequency)

A checkpoint is a fact that looks like this, for example:

{ 
    epoch: 167,
    lastLeader: 27,
    lastBlockIndexByLeader: 56,
    lastBlockHashByLeader: 'aaaa...'
}

If such a message is saved on many blockchains, then even after many years it can be trusted, because in order to potentially change it, attackers would need to compromise most of the blockchains.

TLDR - having found such a message in 2/3 of the blockchains that we will use to maintain checkpoints, you can be confident about the validity of your own copy of the state and blockchain.

How to find checkpoints ?

The same is here ⇒ Solution

In explorer visit the page about checkpoints'

Here for each epoch, a list of checkpoints and links to the corresponding transactions in other blockchains is available.

Here Bitcoin, Ethereum and Solana are used as examples

In many cases, it is recommended to trust the validity of the epoch data where 2/3N checkpoints are available. This is a guarantee that the checkpoint is made forever

Long story short you can trust this

And this:

But doubt this: