It doesn't mean Linux is not capable of encrypting or pad-locking the files, it is equally capable of doing that, only, Linux views passwording a file as NOT NECESSARY anymore because the owner of the file has absolute power to SET PERMISSION CONTROL IN EVERY FILE.
a) To have a file ONLY accessible by the owner (you) do this:
user@host--$: chmod 0700 /folder/file-name
b) If you want a group of chosen users to have access to the file you need to do it in two (2) steps, to wit:
Step 1 - Create a group of users. Do this using your GUI Users/Group applet. Then, in the same applet make the privileged/chosen users to become members of that group (you may need root password to change the /etc/passwd file;
Step 2 - Set the file or folder permission to be accessible only by that group. Use one of those user(s) account when you create the folder or file, then set the folder permissions, in terminal do this:
user@host--$ chmod -R 0750 /folder_name
This will set also all files and sub-directories within it to similar permissions. The privileged member users to the same group of the one who created it will access the file without need of password.
If you need something more than this you can use secure socket layer or gnu's gpg, you may learn about it by reading here
, and here
, or you can download a third party encryptor click here
Hope this helps.