sub read_bytes {
   my ($fh, $to_read) = @_;
   $buf = '';
   while ($to_read) {
      <b>my $bytes_read = read($FH_decrypted, $buf, length($buf));</b>
      die("$!\n") if !defined($bytes_read);
      die("Unexpected end of file\n") if !$bytes_read;
      $to_read -= $bytes_read;
   }
   return $buf;
}