On Tue, Jan 10, 2023 at 8:22 AM Nick Mathewson nickm@torproject.org wrote:
Filename: 342-decouple-hs-interval.md Title: Decoupling hs_interval and SRV lifetime Author: Nick Mathewson Created: 9 January 2023 Status: Draft# Motivation and introduction
I think there's another issue to address here too: the offset from the Unix Epoch at which the first Time Period begins. According to rend-spec-v3,
"we want our time periods to start at 12:00UTC every day, so we subtract a "rotation time offset" of 12*60 minutes from the number of minutes since the epoch, before dividing by the time period (effectively making "our" epoch start at Jan 1, 1970 12:00UTC)."
But this isn't exactly what the C Tor implementation does. In `hs_get_time_period_num(),` it defines the offset as `sr_state_get_phase_duration()`, which is tied to the voting interval and the constant SHARED_RANDOM_N_ROUNDS (which is 12).
David, do you have any thoughts on the right solution here? Some options are: * We could document the current behavior. * We could add a consensus parameter for the time period offset. * We could define the time period offset as exactly 12 hours in all cases. (I guess this would break test networks though?) * Something else?
best wishes,