新增的表单控件keygen元素的操作实例是什么？

//firefox: 1->usr_name=1&security=MIIBOjCBpDCBnzANBgkqhkiG9w0BAQEFAAOBjQAwgYkCgYEA1HUwmm%2B75QTnuDXC%0D%0AnUsL8cD8KkncFnA6TRaJttYss0Oi6dVzOPOtdK0O7wxD4%2BIhjSMZRD%2FddKFciZw0%0D%0AURyAimXxe%2FlDKmR3Nb1SzmqA7RJnns%2FA%2BduiYeeIIiMSL2ydUOvQvVFYMtaDkWra%0D%0AtpQfeWv1Hjz9hb7HlGzOUbtGrAECAwEAARYAMA0GCSqGSIb3DQEBBAUAA4GBAJ0I%0D%0ATWv7CdcNzqkaq5OpN6GHWtrlIpD5UAL%2FOiFDICb%2F8PFgV7FQk0MaGwj5XzQfEu4B%0D%0A6YlAbyz2l91I9%2FJW6Oerru5wL646OpvnTvD2U%2FzByU%2FHWp0BRNeDqntMAsGvzl6D%0D%0AoNsHTwLjDUGYVILge4syfcQVRpFRZiyVRaNlIJT9#<form action="#">
    Username: <input type="text" name="usr_name" />
    Encryption: <keygen name="security"  />
    <input type="submit" />
</form>