Add the ECDSA algorithms (remove any key sizes you do not wish to allow) to the list of auth-publickey signature-algorithms (within the <authentication-methods> element) in your ssh-broker-config.xml:

<auth-publickey signature-algorithms="ecdsa-sha2-nistp256,ecdsa-sha2-nistp384, \
    ecdsa-sha2-nistp521,ssh-dss,ssh-rsa,ssh-dss-sha256@ssh.com, \
    ssh-rsa-sha256@ssh.com,x509v3-sign-dss,x509v3-sign-rsa, \
    x509v3-sign-dss-sha256@ssh.com, x509v3-sign-rsa-sha256@ssh.com">
  <key-selection policy="automatic">
  </key-selection>
</auth-publickey>

	Note
	To enable ECDSA keys for X.509, add also the following to the signature-algorithms list: x509v3-ecdsa-sha2-nistp256,x509v3-ecdsa-sha2-nistp384,x509v3-ecdsa-sha2-nistp521.

Create the ECDSA user key with ssh-keygen-g3. For more information on ssh-keygen-g3, refer to the Tectia Client User Manual.

Use ssh-keygen-g3 with –t (type) ecdsa. Once generated, the resulting .pub file should be uploaded to the target server.

	Note
	Do this under the correct user account. The example below is using the root user.

[root@host ~]# ssh-keygen-g3 -t ecdsa 
Generating 256 bits ECDSA key on nistp256 curve
Key generated. 
256-bit ecdsa, root@host.example.com, Mon Aug 24 2015 09:57:24 -0400 
Passphrase : 
Again      : 
Key is stored with NULL passphrase...
...
Private key saved to /root/.ssh2/id_ecdsa_256_a 
Public key saved to /root/.ssh2/id_ecdsa_256_a.pub