OpenWrt/LEDE Project

  • Status Unconfirmed
  • Percent Complete
    0%
  • Task Type Bug Report
  • Category Packages
  • Assigned To No-one
  • Operating System All
  • Severity High
  • Priority Very Low
  • Reported Version openwrt-19.07
  • Due in Version Undecided
  • Due Date Undecided
  • Private
Attached to Project: OpenWrt/LEDE Project
Opened by Kurt Roeckx - 09.02.2021

FS#3613 - Overestimated entropy in urgnd

I was looking at the entropy collected by the jitterentropy library that urngd is using. I’ve filed a bug against the library at https://github.com/smuellerDD/jitterentropy-library/issues/21

What I’m seeing it that is overestimates the amount of entropy collected. On my desktop machine this is at least a factor of 100. I’ve not looked at any of my devices using OpenWRT yet, but I expect it to be worse there.

Urngd has an oversampling factor, which is currently set to 2, meaning the factor is 2 time smaller. The oversampling in urngd currently collects twice as many bytes (64), and then tells the kernel that it contains 32 byte / 256 bit of entropy. The library also supports oversampling itself, it’s a parameter to the jent_entropy_collector_alloc function.

I suggest that you set the oversampling factor to at least 1000.

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