OSPF - OSPFv3 authentication

OSPFv3 does not have built-in authentication like OSPFv2. Instead, it relies on IPv6's built-in authentication methods. Specifically, OSPFv3 uses the IPv6 Authentication Header (AH) or the IPv6 Encapsulating Security Payload (ESP) header to ensure the integrity, authentication, and confidentiality of routing exchanges. These headers provide the necessary security features to protect OSPFv3 communications.

The security policy for OSPFv3 is a combination of the Security Parameter Index (SPI) and the key used to create and validate the hash value, which is essentially a Pre-Shared Key (PSK) within the IPsec framework.

https://networklessons.com/ipv6/ospfv3-authentication-and-encryption/