# Why does Zcash doesn’t randomnize γ in the Sapling’s Groth16 verifying key ? Is sampling only 1 of γ or δ enough to prevent forgeries ?

**URL:** <https://forum.zcashcommunity.com/t/why-does-zcash-doesn-t-randomnize-in-the-sapling-s-groth16-verifying-key-is-sampling-only-1-of-or-enough-to-prevent-forgeries/49052>\
**Category:** Technology\
**Created:** [October 17, 2024, 12:04pm UTC](https://forum.zcashcommunity.com/t/why-does-zcash-doesn-t-randomnize-in-the-sapling-s-groth16-verifying-key-is-sampling-only-1-of-or-enough-to-prevent-forgeries/49052 "2024-10-17T12:04:26Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![ytrezq](https://sea2.discourse-cdn.com/zcash/user_avatar/forum.zcashcommunity.com/ytrezq/32/28174_2.png) [@ytrezq](https://forum.zcashcommunity.com/u/ytrezq)\
**Post date:** [October 17, 2024, 12:04pm UTC](https://forum.zcashcommunity.com/t/why-does-zcash-doesn-t-randomnize-in-the-sapling-s-groth16-verifying-key-is-sampling-only-1-of-or-enough-to-prevent-forgeries/49052/1 "2024-10-17T12:04:26Z")

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I’m unable to examine the [Sapling’s verifying key](https://forum.zcashcommunity.com/t/where-to-download-the-sapling-s-verifying-key-as-text/) but from what I’m seeing in the code of phase2’s trusted setup only \delta is updated from the curve’s generator’s point leaving \gamma on the curve’s value of the generator.

According to page 17 [from groth16](https://eprint.iacr.org/2016/260.pdf), α ; β ; γ ; δ should be sampled by the trusted setup. [This article describe an attack](https://github.com/RareSkills/zk-book/blob/9289f45462a7fe73b7462cf6c45e5c76af97001d/content/groth16/en/groth16.md?plain=1#L276). But it seems to only work when \gamma, \delta are equal. [Nerveless it also states both values should be sampled and not just 1](https://github.com/RareSkills/zk-book/blob/9289f45462a7fe73b7462cf6c45e5c76af97001d/content/groth16/en/groth16.md?plain=1#L303).

Does this means in reality that the 2 G\_2 points representing public inputs should just have unknown discrete logarithms relation in order to thwart any possible attack ?