+my $timestamp = 0;
+if (defined $ENV{PEM2OPENPGP_TIMESTAMP}) {
+ $timestamp = ($ENV{PEM2OPENPGP_TIMESTAMP} + 0);
+} else {
+ $timestamp = time();
+}
+
+my $flags = 0;
+if (! defined $ENV{PEM2OPENPGP_USAGE_FLAGS}) {
+ $flags = $usage_flags->{authenticate};
+} else {
+ my @ff = split(",", $ENV{PEM2OPENPGP_USAGE_FLAGS});
+ foreach $f (@ff) {
+ if (! defined $usage_flags->{$f})
+ die "No such flag $f";
+ $flags |= $usage_flags->{$f};
+ }
+}