GCIH · Question #711
What type of hash is used in the password hash below?
The correct answer is B. SHA-512. A $6$ prefix in a Linux /etc/shadow hash entry identifies it as a SHA-512 crypt hash using the modular crypt format.
Question
What type of hash is used in the password hash below?
Options
- ADES
- BSHA-512
- CMD5
- DSHA-256
How the community answered
(20 responses)- B90% (18)
- C5% (1)
- D5% (1)
Why each option
A $6$ prefix in a Linux /etc/shadow hash entry identifies it as a SHA-512 crypt hash using the modular crypt format.
Traditional DES-based Unix crypt hashes have no dollar-sign prefix and are exactly 13 characters long - they are a legacy, weak scheme no longer used by default.
Linux systems use a modular crypt format where a numeric prefix in the hash string identifies the algorithm - $6$ designates SHA-512. SHA-512 is the modern default hashing scheme on most Linux distributions, applying the SHA-512 digest with a random per-user salt and configurable iteration rounds to resist brute-force and rainbow table attacks.
MD5 password hashes in the modular crypt format use the $1$ prefix, not $6$, and produce a 22-character encoded hash value.
SHA-256 hashes in the modular crypt format use the $5$ prefix - SHA-512 is identified by $6$, so these two are distinct and not interchangeable.
Concept tested: Linux /etc/shadow password hash algorithm identification
Source: https://man7.org/linux/man-pages/man3/crypt.3.html
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