You can encrypt your files so that others cannot open them without your password. To do so, use the Apple File Security program (in the Security folder inside the Applications folder). The program also automatically compresses files so they take up less disk space.
Apple File Security uses a 56-bit key to encrypt files.
Note: You cannot encrypt folders, disks, volumes, items in the System Folder, or files that are open or locked.
Encrypting files
To encrypt a file:
1. Open the File menu and choose Open, then locate the file you want to encrypt. Tip: You can also choose Encrypt from the Finder's File menu. If you open an alias, the file that the alias refers to will be encrypted.
2. Enter a password for the file. Be sure to remember your password so you can enter it to decrypt the file. By default, the password is added to your keychain. To prevent it from being added, deselect the "Add to keychain" checkbox.
3. Click Encrypt. Tip: As long as the file is not a stationery pad document, you can also encrypt (or decrypt) the file by dragging it to the Apple File Security icon.
Decrypting files
To decrypt a file:
1. Double-click the file you want to decrypt.
2. Enter the password that was used to encrypt the file. If you added this password to your keychain and your keychain is unlocked, you won't be asked to enter your password here.
3. Click Decrypt. After you decrypt the file, the password you used to encrypt it is removed from your keychain.