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Feat Nova incremental inclusion verification #153

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merged 6 commits into from Sep 13, 2023

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@enricobottazzi enricobottazzi commented Sep 8, 2023

This PR adds an example of how a full flow of Incremental Proof of Inclusion verification can be performed using Nova as a prover. A more detailed explanation can be found in Incremental Inclusion Verfication.

  • zk_prover/circom, contains the circuit implementation for the nova prover + some template circuits from circomlib
  • examples/nova_incremental_verifier.rs contains the script to run the example
  • examples/build contains the wasm and r1cs artifacts automatically generated by circom after the circuit compilation.

As you will see in the example script, I had to add different support functions related to the Merkle Sum Tree. The issue comes from the fact that the Poseidon Hasher used in circomlib behaves differently from our own implementation of the Poseidon Hasher so I couldn't use our MerkleSumTree struct. Luckily I found a rust library poseidon-rs that is compatible with circom's posiedon. Unfortunately, I meant recreating all the utils with this different hasher.

If we decide to move forward with this implementation, we need to find a way to create compatibility between the 2 hashers.

@enricobottazzi enricobottazzi marked this pull request as ready for review September 8, 2023 15:00
@enricobottazzi enricobottazzi changed the title Feat incremental inclusion verification Feat Nova incremental inclusion verification Sep 11, 2023
right_in_range[i] = Num2Bits(8*N_BYTES);

left_in_range[i].in <== left_balances[i];
right_in_range[i].in <== right_balances[i];
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Is it enough to just assign the inputs of Num2Bits without checking the output?

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Copying from internal discussion

"My understanding is that to perform range check on a number we don’t really have to consume the output, we just want to check that the number can be expressed in a specific bit range. So if the number doesn’t fit this assertion will fail => https://github.com/iden3/circomlib/blob/master/circuits/bitify.circom#L38"

You can also reproduce this on ZKREPL by following this gist.

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Good alternative approach.
Perhaps we can move this outside of the examples folder in the future.

@alxkzmn alxkzmn merged commit bc63f43 into master Sep 13, 2023
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@enricobottazzi enricobottazzi deleted the feat-incremental-inclusion-verification branch November 21, 2023 14:32
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3 participants