What is Strong Customer Authentication (SCA)?

SCA or strong customer authentication is an authentication procedure based on the use of at least two of the following elements:

1. knowledge (something only the user knows)
2. possession (something only the user possesses)
3. inherence (something the user is)

Elements must be independent (in that the breach of one does not compromise the reliability of the others) and the process should be designed to protect the confidentiality of the authentication data. An example of SCA is Chip (possession) and Pin (knowledge) which has been common practice in physical card transactions for years. However, for many internet transactions and contactless payments, a second authentication factor is missing.

PSD2 requires payment service providers to use SCA, i.e. electronic payments must be performed with multi-factor authentication.