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penumbra-zone / penumbra

Penumbra is a fully private proof-of-stake network and decentralized exchange for the Cosmos ecosystem.
https://penumbra.zone
Apache License 2.0
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docs: document maximum issuance of staking tokens #3728

Open erwanor opened 8 months ago

erwanor commented 8 months ago

Is your feature request related to a problem? Please describe. In #3661, we simplified validator voting power calculation by measuring it in units of staking tokens. However, CometBFT imposes a hard limit of $2^{60} - 1$.

This is not hugely problematic. Assuming a staking token denomination unit of $10^6$, integral staking token quantities take at least 20 bits to represent. This leaves 40 bits (or $10^{12}$) to represent the quantity of tokens (a trillion).

However, we should document this in the specification. If this ever becomes a problem, for example for some re-using the penumbra blockchain stack with parameters that work for them, there is always the option of using a constant factor to rescale the voting power so that it fits the CometBFT limit.

erwanor commented 8 months ago

It would generally be good to have a "Getting started" guide accompanied by a list of known limitations/workaround for prospective users of the penumbra stack.