Hello! In eth network and other networks, there is a great solution to generate random number - Chainlink VRF.

But Chainlink VRF does not support zk-rollup and the network I need.

How can I generate random number in zk-rollup solidity networks so that it cannot be predicted (and it doesn't have to be detralized oracl)?

I also tried generating a number in a smart contract using abi.encodePacked(now,block.difficulty,arr.length); But such a number can be predicted.