Chapter 1 What’s New for FortiOS 5.2.1 : IPsec VPN : Internet Key Exchange (IKE) : Authentication Methods
  
Authentication Methods
Three new authentication methods have been implemented for IKE: ECDSA-256, ECDSA-384, ECDSA-521.
In order to support these three methods, the following changes have been made to the CLI:
1. rsa-signature has been renamed to signature for both policy-based and interface-based IPsec VPN.
2. rsa-certificate has been renamed to certificate for both policy-based and interface-based IPsec VPN.