These constants are used with wodSSHD key managment object called KeyPair. You can access it through wodSSHD1.Keys property.

SSH2 protocol specification defines RSA cipher as default, and it should be supported by all clients/servers, so it is advised you should use it. However, there could be client implementations that support only DSA (due to RSA patent, which has in the meantime expired) so you should also use DSA. wodSSHD allows you to Generate (or Load) both types at the same time.