code: public void associateCommand(SshPublicKey key, String command)
  			throws SshException, PublicKeySubsystemException {
  
  		try {
  
  			Packet msg = createPacket();
  			msg.writeString("command");
  			msg.writeString(key.getAlgorithm());
  			msg.writeBinaryString(key.getEncoded());
  			msg.writeString(command);
  
  			sendMessage(msg);
  
  			readStatusResponse();
  
  		} catch (IOException ex) {
  			throw new SshException(ex);
  		}
  
  	}
docs: Associate a command with an accepted public key. The request will fail if
  the public key is not currently in the users acceptable list. Also some
  server implementations may choose not to support this feature.
  
  @param key
  @param command
  @throws SshException
  @throws PublicKeyStatusException