• ハードウェア：BeagleBone Green Wireless
• Linux 情報は以下の通り

$ uname -r
4.19.94-ti-r35
$ cat /etc/debian_version 
10.3

$ zcat /proc/config.gz | grep -i hw_random
CONFIG_HW_RANDOM=y
# CONFIG_HW_RANDOM_TIMERIOMEM is not set
CONFIG_HW_RANDOM_OMAP=y
CONFIG_HW_RANDOM_VIRTIO=m
CONFIG_HW_RANDOM_TPM=y

ハードウェア乱数が使えそうです．

$ sudo apt-get install rng-tools

インストールできたら，動作状態を確認します．

$ sudo systemctl status rng-tools.service
● rng-tools.service
   Loaded: loaded (/etc/init.d/rng-tools; generated)
   Active: active (running) since Mon 2020-02-24 22:43:38 JST; 2min 39s ago
     Docs: man:systemd-sysv-generator(8)
  Process: 2162 ExecStart=/etc/init.d/rng-tools start (code=exited, status=0/SUCCESS)
    Tasks: 4 (limit: 1024)
   Memory: 292.0K
   CGroup: /system.slice/rng-tools.service
           └─2164 /usr/sbin/rngd -r /dev/hwrng

Feb 24 22:43:38 beaglebone systemd[1]: Starting rng-tools.service...
Feb 24 22:43:38 beaglebone rng-tools[2162]: Starting Hardware RNG entropy gatherer daemon: rngd.
Feb 24 22:43:38 beaglebone systemd[1]: Started rng-tools.service.
Feb 24 22:43:38 beaglebone rngd[2164]: rngd 2-unofficial-mt.14 starting up...
Feb 24 22:43:38 beaglebone rngd[2164]: entropy feed to the kernel ready

haveged を停止します．

$ sudo systemctl stop haveged.service
$ sudo systemctl disable haveged.service

再起動して，エントロピーの値を調べてみます．

$ cat /proc/sys/kernel/random/entropy_avail
2086

https://archlinuxjp.kusakata.com/wiki/Haveged によると，この数値が1000以下だと暗号処理などで十分なエントロピーが貯まるまで止まるようですが，2000を超えているので問題なさそうです．