First creating a big file of random data which later on would be the encrypted content:
dd if=/dev/urandom of=rand.dat bs=1024 count=1000000
will create 1GB of random data.
Then checking via rngtest:
cat rand.dat | rngtest rngtest: starting FIPS tests... rngtest: entropy source exhausted! rngtest: bits received from input: 8192000000 rngtest: FIPS 140-2 successes: 409226 rngtest: FIPS 140-2 failures: 373 rngtest: FIPS 140-2(2001-10-10) Monobit: 56 rngtest: FIPS 140-2(2001-10-10) Poker: 27 rngtest: FIPS 140-2(2001-10-10) Runs: 153 rngtest: FIPS 140-2(2001-10-10) Long run: 138 rngtest: FIPS 140-2(2001-10-10) Continuous run: 0 rngtest: input channel speed: (min=2.070; avg=21.267; max=18.626)Gibits/s rngtest: FIPS tests speed: (min=113.533; avg=163.438; max=171.833)Mibits/s rngtest: Program run time: 48202690 microseconds
And at last checking via dieharder:
dieharder -g 201 -f rand.dat -a