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summa-dev / summa-solvency

Monorepo for Summa Proof of Solvency Protocol
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Find out how Blinding Factors affect Grand Sum Calculation #235

Closed enricobottazzi closed 9 months ago

enricobottazzi commented 10 months ago

The goal is to understand how the blinding factors affect the grandsum calculation and if a malicious prover can exploit its feature. For example by overflowing the grandsum.

alxkzmn commented 10 months ago

TLDR: the blinds don't affect the grand sum.

For normal advice, not just the blinds are random but the columns themselves are filled with random cell values after the circuit values. To the contrary, the unblinded advice columns are not filled with any random values:

https://github.com/summa-dev/halo2/blob/v2-PoC/halo2_proofs/src/plonk/prover.rs#L366-L378

The blinding factors also do not contribute to the KZG commitment.

https://github.com/summa-dev/halo2/blob/v2-PoC/halo2_proofs/src/poly/kzg/commitment.rs#L305-L316

enricobottazzi commented 9 months ago

Thanks for clarifying that. Closing the issue