# zkBridge vs zkRollup

When it comes to uploading election results from a blockchain-based voting platform to Ethereum, there are two main approaches: the zkBridge and the zkRollup. Both methods aim to provide verifiable and binding results in a decentralized manner, but they differ in their approach, benefits and constraints.

The zkBridge approach is based on the transfer of a State Hash Root from the voting platform's blockchain to Ethereum. This State Hash Root represents the current state of the voting platform and can be used to verify the data stored within the platform by generating a MerkleProof. The zkBridge allows for greater flexibility in terms of data storage, as the voting platform's blockchain does not need to be Snarks friendly, and it allows for the storage of arbitrary data. Additionally, this approach makes it easier to implement anonymous voting, which is already supported by the voting platform's blockchain. The circuit for the zkBridge is relatively simple and only needs to aggregate the signatures of validators on the voting platform's block headers.

On the other hand, the zkRollup approach is based on the aggregation of votes within a single zkSnark. The zkSnark acts as a proof that the results are correct and can be verified on Ethereum. This approach provides a more efficient way to upload results to Ethereum, as it reduces the amount of data that needs to be transferred. However, this approach requires a zkSnark circuit to be defined for each type of data being uploaded, and the circuit must be able to validate the data in a manner that is compatible with Ethereum. Additionally, implementing anonymous voting using this approach is more complicated and requires a recursive zkSnark circuit.

In conclusion, both the zkBridge and zkRollup approaches have their advantages and disadvantages, and the best approach will depend on the specific requirements of the voting platform. If the platform requires a flexible and simple solution for uploading arbitrary data, including anonymous voting results in the short-mid term, then the zkBridge approach may be a better choice. However, if the platform requires a more efficient and compact solution for uploading results, then the zkRollup approach may be a better choice.