The eIDAS Regulation defines a simple electronic signature as follows: "data in electronic form attached to or logically associated with other electronic data used by the signer to sign". A simple electronic signature is usually one in which the signer is asked to accept some condition by completing a checkbox or an OTP code and does not have the ability to properly identify the signer.
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For its part, the eIDAS Regulation defines an advanced electronic signature as a: "the electronic signature that meets the requirements referred to in Article 26". The requirements referred to in Article 26 of the eIDAS Regulation are the following: (i) it must be uniquely linked to the signer; (ii) it must be capable of identifying the signer; (iii) it must be created using electronic signature creation data that the signatory can use, with a high level of confidence, and under its exclusive control; and (iv) it must be linked to the data signed by it in such a way that any subsequent modification of the data is detectable. Unlike the simple electronic signature, with the advanced electronic signature the signer normally makes a signature -properly speaking- with the finger or with the mouse, and the signer is duly identified.
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Although both electronic signatures are legally valid, the advanced electronic signature is more secure since it allows obtaining information to properly identify the signer and detect any subsequent changes. Therefore, it is recommended to use the simple electronic signature in those matters where it is not vital to properly identify the signer, while we recommend using the advanced electronic signature for all those documents or agreements that have sufficient relevance and where it is necessary or sufficiently useful to properly identify the signer.