sub sign {
    my ($self, %params) = @_;
    my $key = $params{Key}; my $M = $params{Message} || $params{Plaintext};
    return $self->error("No Key parameter", \$M, \%params) unless $key;
    return $self->error("No Message or Plaintext parameter", \$key, \%params) un
less $M;
    my $k = octet_len ($key->n);
    my $salt = makerandom_octet (Length => $self->{hlen});
    my $em = $self->encode ($M, $salt, $k-1);
    my $m = os2ip ($em);
    my $sig = $self->{primitives}->core_sign (Key => $key, Message => $m);
    my $S = i2osp ($sig, $k);
    return ($S, $salt) if wantarray;
    return $S;
}