osx - chmod unable to change permissions -

I am facing a troubled problem. It has been very disappointing for my school to work on the Coresara Startup Class I am using a computer in I'm trying to connect to an Amazon EC2 example. I checked the permissions that I downloaded the important pair.

  Mac 5-Library: Startup Ruahu 21 $ LS-L Total 6 -R-R-R-RW-1 1 RAH 1 99 108 16 9 22 Jun 22 16:45 Startup-Class -Key   
 So, it's not safe. So I have to change the permissions. I try:  
  Mac 5-Library: startup roh21 $ chmod 400 startup-class-key.pem mac5- library: startup roh21 $ ls -l total 6-r-rr - - @ 1 roh21 108 16 9 22 Jun 22 16:45 startup-class-key.pem   
 Still have read permissions for everyone just to show that I do Mac 5-Library: Startup RAH 21 $ chmod 600 Startup-Class-KPM Mac 5-Library: Startup RAH 21 $ LS-L Total 6-RW-RW- Rw- @ 1 roh21 108 1692 June 22 16:45 startup-class-key.pem   
 Is it impossible to change permissions for user without root permissions? I am grateful for any kind of help.  
 
 
 
 I have my  ~ /.ssh  folder and then  chmod < Changed the permissions with / code>. did so.  
 To provide more information, the permissions for the ssh folder,  
  drwx ------ 8 roh21 108 272 Jun 26 17:26 .ssh < / Code>  
 and the permissions in the folder I used initially  
  drwxrwxrwx 2 roh21 108 2048 Jun 23 06:32 startup   
 I'm curious about why after several attempts with the  chmod -R  option I could not change permissions in the  startup  folder  < P> In addition to this, note that I In Ibreri'm using Mac OS X.