What are the two authentication methods supported by FortiGate for IPsec IKEv1?

The choice of pre-shared key and certificate signature as the authentication methods supported by FortiGate for IPsec IKEv1 is correct. In the context of IKEv1 (Internet Key Exchange version 1), pre-shared keys (PSK) provide a straightforward way to authenticate peers by using a shared secret, which is a string of characters known only to both parties. This method is easy to implement and is often used for site-to-site VPNs.

On the other hand, certificate signature offers a more secure method of authentication by using digital certificates. In this case, each peer has a certificate issued by a trusted certificate authority (CA). The certificate contains the public key and other identifying information, allowing the parties to authenticate each other based on their certificates rather than relying on a shared secret.

This combination of pre-shared keys for simpler setups and certificate signatures for more secure, scalable deployments makes the chosen answer accurate for the authentication methods supported by FortiGate in this context. The other options do not align with the authentication methods recognized in the context of IKEv1, as they present either incorrect pairs or methods not applicable within that framework.