When talking about electronic signatures, strong authentication means authenticating the signer by more than one means. In comparison light authentication occurs by means of just one method, such as a password.

Examples of strong authentication methods:
• Tupas authentication, based on online bank IDs and changing password lists
• Password and email confirmation or phone call
• Password and biometric feature, such as fingerprints or FaceID

Strong authentication methods include:
• Finnish bank IDs and mobile ID
• Swedish and Norwegian BankID systems
• Danish NemID