public function addConfiguration(NodeDefinition $node)
    {
        $node
            ->children()
                ->scalarNode('curve')
                    ->validate()
                        ->ifTrue(self::checkCurve())
                        ->thenInvalid('Unsupported curve. Please use "P-256", "P-384" or "P-521".')
                    ->end()
                    ->isRequired()
                ->end()
            ->end();
        parent::addConfiguration($node);
    }
public function addConfiguration(NodeDefinition $node)
    {
        $node
            ->children()
                ->scalarNode('curve')
                    ->validate()
                        ->ifTrue(self::checkCurve())
                        ->thenInvalid('Unsupported curve. Please use "P-256", "P-384" or "P-521".')
                    ->end()
                    ->isRequired()
                ->end()
            ->end();
        parent::addConfiguration($node);
    }
{@inheritdoc}