Random generator

• This how-to describes the method for optimizing RNG on OpenWrt.
• It may help to minimize system startup time on low performance devices.

• Minimize startup time for cryptography-dependent services.
  • Avoid potential deadlock states and race conditions.

Provide fast RNG with rng-tools.

# Install packages
opkg update
opkg install rng-tools
 
# Configure RNG
uci set system.@rngd[0].enabled="1"
uci commit system
/etc/init.d/rngd restart

Test the entropy pool size.

sysctl kernel.random.entropy_avail

Use rngtest to check the randomness of data.

RNG_DEV="$(uci get system.@rngd[0].device)"
rngtest -c 1000 < ${RNG_DEV}

Collect and analyze the following information.

# Restart services
/etc/init.d/log restart; /etc/init.d/rngd restart
 
# Log and status
logread -e rngd; pgrep -f -a rngd
 
# Persistent configuration
uci show system

Use software RNG by default.

# Use software RNG
uci set system.@rngd[0].device="/dev/urandom"
uci commit system
/etc/init.d/rngd restart

Use hardware RNG if available.

# Use hardware RNG
uci set system.@rngd[0].device="/dev/hwrng"
uci commit system
service urngd disable && service urngd stop
/etc/init.d/rngd restart