Based on the principles of integrity, authenticity, not repudiation and confidentiality has built a significant infrastructure getting provide all these values added to electronic communications.

Thus, security view from a technical level is given by asymmetric key cryptography applied to the electronic signature of documents.

There is another level, legal, which is necessary security. In the case of Spain is guaranteed through the law 59/2003,19 December, electronic signature and rules (HAT) No 910/2014 the European Parliament and of the board 23 July 2014 on electronic identification and services of confidence for electronic transactions in the internal market and repealing the directive 1999/93CE.

The Regulation (HAT) 910/2014 the European Parliament and of the board 23 July 2014defines the electronic signature distinguishing three types:

• The electronic signature general, are “ data in electronic format annexed to other electronic data or logically associated with them that uses the signatory to sign ”.
• The advanced electronic signature is "the electronic signature that is linked to the signatory singly, allows you to identify the signatory, which has been created using data from creating the electronic signature that the author can use, with a high level of confidence, within its exclusive control and is linked to the data signed by the same fashionable such that any subsequent changes in the same is detectable ”.
• The electronic signature is “ a qualified advanced electronic signature that is created by a qualified device electronic signature and that is based on a qualified certificate of electronic signature ”. An electronic signature will have a qualified legal effect equivalent to a signature.

The legislation in force more prominently on the electronic signature at European level and state is as follows:

• At European level:
  • Regulation (HAT) 910/2014 the European Parliament and of the board 23 July 2014 on electronic identification and services of confidence for electronic transactions in the internal market and repealing the directive 1999/93/CE.
  • Directive 2000/31/CE of the European Parliament and of the council, 8 June 2000 on certain legal aspects of services of the information society, in particular electronic commerce in the internal market (e-commerce directive).
  • Regulation (HAT) 2016/679 the European Parliament and of the board 27 April 2016on the protection of individuals with regard to the treatment of personal data and on the free movement of such data and repealing the directive 95/46/CE.

• At state level:
  • Law 59/2003, 19 December, electronic signature.
  • Law 34/2002, 11 of July, on Services of the Information Society and Electronic Commerce.
  • Law 56/2007, 28 December, measures of momentum of the information society.
  • Organic Law 3/2018, 5 December, of protection of personal data and guarantee of the digital rights.