FS#3613 - Overestimated entropy in urgnd #8644
Labels
core packages
pull request/issue for core (in-tree) packages
flyspray
release/19.07
pull request/issue targeted (also) for OpenWrt 19.07 release
kroeckx:
I was looking at the entropy collected by the jitterentropy library that urngd is using. I've filed a bug against the library at smuellerDD/jitterentropy-library#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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