Which legacy password storage method is commonly used on many UNIX flavors?

• A. DES-based password scheme
• B. MD5-based password scheme
• C. SHA-256 based
• D. Argon2

Answer: (A)

The main idea is recognizing what was used historically for UNIX password hashing. The DES-based crypt method is the classic approach that earliest UNIX systems used: it applies the DES cipher to the password with a salt and produces a 13-character hash. This design is considered legacy now because it relies on a only 56-bit effective key space, which makes it far easier to crack with modern hardware. It’s the method you’d encounter as the old, compatibility-driven choice on many UNIX flavors, even though newer schemes exist.

The other options represent newer, stronger approaches. MD5-based crypt (md5crypt) came after DES and improved security, while SHA-256 and SHA-512 crypt (sha-crypt) are widely used on modern systems with stronger resistance to brute-force attacks. Argon2 is a newer, highly secure option that isn’t as commonly deployed as the default on traditional UNIX password storage yet.