PREVRANDAO should be able to return value of a public input instead of difficulty/0

Question

PREVRANDAO should be able to return value of a public input instead of difficulty/0

pgebheim opened this issue a year ago · comments

Discussion today was that this could be added with the value as an external input.

@wborgeaud could you elaborate?

wborgeaud · Answer 1 · Thu Aug 31 2023 16:12:36 GMT+0800 (China Standard Time)

So currently our implementation of PREVRANDAO (0x44) returns the difficulty field of the block header (which is always 0 post-merge).
As explained in EIP-4399, we should instead return the mixHash field of the block header. So to fix this issue we just have to add mixHash to the block metadata and return it in sys_prevrandao.
I think we can just have mixHash be unconstrained in Plonky2 and assume it's been verified upstream in the consensus layer.