Generating random data with OpenSSL

One way to produce lots of seemingly random, hard to compress data is to leverage AES encryption through OpenSSL. This can be faster than just reading data from /dev/urandom as modern CPUs typically have dedicated AES instruction sets which openssl can leverage.

For OpenSSL 1.1 onwards, using current epoch as the seed:

openssl enc -aes-256-ctr -pbkdf2 -pass pass:"$(date '+%s')" < /dev/zero

Comparison to /dev/urandom

On a 6-core Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz machine, this is 3-4 times faster than reading directly from /dev/urandom:

$ timeout 15s openssl enc -aes-256-ctr -pbkdf2 -pass pass:"$(date '+%s')" < /dev/zero | pv > /dev/null
20.7GiB 0:00:15 [1.38GiB/s]

$ timeout 15s pv < /dev/urandom > /dev/null
6.41GiB 0:00:15 [ 470MiB/s]