Petter Reinholdtsen

A few days ago I ordered a small batch of the ChaosKey, a small USB dongle for generating entropy created by Bdale Garbee and Keith Packard. Yesterday it arrived, and I am very happy to report that it work great! According to its designers, to get it to work out of the box, you need the Linux kernel version 4.1 or later. I tested on a Debian Stretch machine (kernel version 4.9), and there it worked just fine, increasing the available entropy very quickly. I wrote a small test oneliner to test. It first print the current entropy level, drain /dev/random, and then print the entropy level for five seconds. Here is the situation without the ChaosKey inserted:

% cat /proc/sys/kernel/random/entropy_avail; \
  dd bs=1M if=/dev/random of=/dev/null count=1; \
  for n in $(seq 1 5); do \
     cat /proc/sys/kernel/random/entropy_avail; \
     sleep 1; \
  done
300
0+1 oppføringer inn
0+1 oppføringer ut
28 byte kopiert, 0,000264565 s, 106 kB/s
4
8
12
17
21
%

The entropy level increases by 3-4 every second. In such case any application requiring random bits (like a HTTPS enabled web server) will halt and wait for more entrpy. And here is the situation with the ChaosKey inserted:

% cat /proc/sys/kernel/random/entropy_avail; \
  dd bs=1M if=/dev/random of=/dev/null count=1; \
  for n in $(seq 1 5); do \
     cat /proc/sys/kernel/random/entropy_avail; \
     sleep 1; \
  done
1079
0+1 oppføringer inn
0+1 oppføringer ut
104 byte kopiert, 0,000487647 s, 213 kB/s
433
1028
1031
1035
1038
%

Quite the difference. :) I bought a few more than I need, in case someone want to buy one here in Norway. :)