010-150 · Question #46
Which one of the following statements concerning Linux passwords is true?
The correct answer is D. Passwords are only stored in encrypted form. Linux stores passwords in encrypted (hashed) form, never in plaintext, and there is no master password that can decrypt them.
Question
Which one of the following statements concerning Linux passwords is true?
Options
- AAll passwords can be decrypted using the system administrator's master password.
- BPasswords may never start with a non-letter.
- CUsers cannot change their password once it has been set.
- DPasswords are only stored in encrypted form.
- EPasswords may be at most six characters long.
How the community answered
(50 responses)- A4% (2)
- B12% (6)
- C2% (1)
- D80% (40)
- E2% (1)
Why each option
Linux stores passwords in encrypted (hashed) form, never in plaintext, and there is no master password that can decrypt them.
Linux uses one-way hashing, not encryption, so there is no master password or decryption mechanism that can recover plaintext passwords.
Linux passwords have no restriction preventing them from starting with non-letter characters; special characters and digits are commonly allowed and encouraged.
Users can change their own passwords at any time using the passwd command, subject to any policy restrictions set by the administrator.
Linux stores passwords as one-way cryptographic hashes (historically in /etc/passwd, now in /etc/shadow). Because hashing is a one-way function, the original plaintext password cannot be recovered - even by root. Authentication works by hashing the input and comparing it to the stored hash.
Modern Linux systems support passwords well beyond six characters; older DES-based limits have been replaced by stronger hashing algorithms like SHA-512 that support long passphrases.
Concept tested: Linux password storage and hashing security
Source: https://linux.die.net/man/5/shadow
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