It is an authentication process that validates the identity of the user of a payment service or of the payment transaction (more specifically, whether the use of a payment instrument is authorised). Strong customer authentication is based on the use of two or more elements categorised as knowledge (something only the user knows, e.g. a password or a PIN), possession (something only the user possesses, e.g. the card or an authentication code generating device) and inherence (something the user is, e.g. the use of a fingerprint or voice recognition) to validate the user or the transaction
