Authentication can refer to the following:

• 3D Secure Authentication message sent from the Merchant to the 3-D Secure service provider to obtain cardholder authentication before submitting an Authorisation message via the Acquirer to Visa/Mastercard.
• Card authentication checks that may be carried out at Visa/Mastercard, Thredd (and occasionally the Program Manager on receipt of EHI message) to validate that the card is genuine.
• Cardholder authentication checks that may be carried out at Visa/Mastercard, Thredd (and occasionally the customer on receipt of EHI message) to validate that the cardholder is genuine.

For more information, see the Key Concepts Guide.