Space-faring electronics aren't exactly cost-sensitive - the cost of a cluster of crypto-accelerated CPUs or rad-hardened FPGAs is peanuts compared to the human and launch costs that go into these satellites.

Issue is the satellite was launched 10 years ago with 20-year-old tech. So, calculations of today may not be applicable on them.

Wireguard uses ChaCha20, which to my knowledge neither has nor requires HW acceleration to be fast.

> However, the software performance [of wireguard] is far below the speed of wire.

https://github.com/chili-chips-ba/wireguard-fpga

It's faster on CPUs without dedicated hardware than AES, but that doesn't mean that it's faster than fixed-function AES hardware.