$ echo foo |aes >123   ## password "f"
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
$ xxd 123
0000000: 5361 6c74 6564 5f5f ade9 addb 6d65 c7cd 00f6 4535 6b11 20bb 3bb9 aa91 f4ee 6db1  Salted__....me....E5k. .;.....m.
$ aes -d <123 |xxd
enter aes-256-cbc decryption password:
0000000: 666f 6f0a                                                                        foo.  
$ aes -d <123 |xxd    ## password "026" 
enter aes-256-cbc decryption password:
0000000: 4bf6 0a0c a1dc 465e cf40 d4ad 71e6 87                                            K.....F^.@..q..

$ echo foo |openssl aes-256-cbc -salt -a
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
U2FsdGVkX19lqSi+Z8UoUmfnUqX7QJf+vQwwlyQ0tL4=

$ echo foo |openssl aes-256-cbc -salt |xxd
enter aes-256-cbc encryption password:
Verifying - enter aes-256-cbc encryption password:
0000000: 5361 6c74 6564 5f5f 237d 34c9 d818 28d6  Salted__#}4...(.
0000010: 37f6 db75 cb87 bb5f e689 fd06 9d54 bf8b  7..u..._.....T..

$ echo 'U2FsdGVkX19lqSi+Z8UoUmfnUqX7QJf+vQwwlyQ0tL4=' |openssl aes-256-cbc -salt -a -d
enter aes-256-cbc decryption password:
bad decrypt
140357412120232:error:06065064:digital envelope routines:EVP_DecryptFinal_ex:bad decrypt:evp_enc.c:539:

$ echo 'U2FsdGVkX19lqSi+Z8UoUmfnUqX7QJf+vQwwlyQ0tL4=' |openssl aes-256-cbc -salt -a -d
enter aes-256-cbc decryption password:
foo

perl programa.pl >claves.txt

use warnings;
use strict;
use Fcntl;
use Time::HiRes qw/time/;
use Parallel::ForkManager;

my $runtime = 5;  ## desired runtime, in seconds
my $nprocs = 0;

sub gen_pks {
    my ($npks) = @_;
    my @pks;
    
    sysopen my $fd, '/dev/urandom', O_RDONLY;
    for (1..$npks) {
        my $read = sysread $fd, my $buf, 256/8 or die "sysread: $!";
        die 'EOF' unless $read;
        warn 'short read' if 256/8 != length $buf;
        push @pks, $buf
    }
    close $fd;

    return \@pks;
}

sub ncpus {
    open my $fd, '<', '/proc/cpuinfo' or die "open: $!";
    my $ncpus = grep { /^processor/ } <$fd>;
    close $fd;
    return $ncpus;
}

my $t0 = time;
my $pm = Parallel::ForkManager->new ($nprocs or ncpus);
$pm->set_waitpid_blocking_sleep (0);
$pm->run_on_finish (sub {
    my $data = pop;
    printf "%s\n", unpack 'H*', $_ for @$data;
});

while (1) {
    last if time-$t0 > $runtime;
    $pm->start and next;
    $pm->finish (0, gen_pks 1e3);
}
$pm->wait_all_children;