According to Article 7.3 of the General Conditions of Tender, for electronic bids, a qualified electronic signature (QES) is required. A qualified electronic signature is an electronic signature that:
Qualified electronic signatures fulfil the legal requirements for a signature with respect to data in electronic form in the same way as handwritten signatures with respect to data on paper.
Bidders are allowed to use any qualified electronic signature that is based on a qualified certificate offered by a certification service provider accredited in the trusted list in accordance with Commission Implementing Decision 2013/662/EU of 14 October 2013 amending Decision 2009/767/EC as regards the establishment, maintenance and publication of trusted lists of certification service providers supervised/accredited by Member States.
See the following links
lists are available for consultation on the following link