Please try the following experiment? Create a new user under os 10.x Assign the following password 123456789 Log out and attemp to login as the user you just created by entering the password as 12345678 Interesting? Now... try to access the users keychain by entering only 12345678. Hmmmmm. I have not thouroughly tested this, but it appears that the os requires the entire password at times, and does not at other times.