create, creates a new 2048 bit RSA key pair and returns a unique ID that can be used to reference this key pair when launching new instances.

create returns an array which contains the keyName, keyFingerprint and keyMaterial.

$ec2_kp = new Zend_Service_Amazon_Ec2_Keypair('aws_key','aws_secret_key');
$return = $ec2_kp->create('my-new-key');

delete, will delete the key pair. This will only prevent it from being used with new instances. Instances currently running with the keypair will still allow you to access them.

delete returns boolean TRUE or FALSE

$ec2_kp = new Zend_Service_Amazon_Ec2_Keypair('aws_key','aws_secret_key');
$return = $ec2_kp->delete('my-new-key');

describe returns information about key pairs available to you. If you specify key pairs, information about those key pairs is returned. Otherwise, information for all registered key pairs is returned.

describe returns an array which contains keyName and keyFingerprint

$ec2_kp = new Zend_Service_Amazon_Ec2_Keypair('aws_key','aws_secret_key');
$return = $ec2_kp->describe('my-new-key');