Which statements about hashing are correct? i. It is a one-way functionii. Used for password storageiii. Can be reversed with the correct keyiv. Ensures data integrity

Question

BlackTom AI · Accepted Answer

Hash functions are one-way cryptographic algorithms that map arbitrary input to a fixed-size digest; this core property determines which statements are true.

1) Relevant knowledge points and concepts
- One-way / preimage resistance: given a hash digest, it should be computationally infeasible to recover the original input.
- Password storage practice: systems store salted, slow cryptographic hashes (e.g., bcrypt, Argon2) of passwords rather than plain text.
- Reversibility vs encryption: reversible transformations (encryption) require a key to decrypt; hashing is not reversible even with a key.
- Data integrity: a hash changes if the input changes, so recomputing and comparing hashes detects tampering.

2) Step‑by‑step reasoning
- Statement i ("It is a one-way function"): True. Cryptographic hashes are designed to be one-way (preimage resistance).
- Statement ii ("Used for password storage"): True. Best practice is to store salted, hashed passwords so original passwords are not stored; correct verification is done by hashing the supplied password and comparing digests.
- Statement iii ("Can be reversed with the correct key"): False. Hashing does not use a key to produce a reversible output. Even keyed constructions (HMAC) are still non-reversible; encryption schemes are reversible with keys, but hashes are not.
- Statement iv ("Ensures data integrity"): True. If you compute a hash of data and later recompute it, any change in the data produces a different hash (assuming no collisions), so hashes are widely used for integrity checks.

3) Calculations / intermediate steps
- No numeric calculations apply; logical evaluation of each statement is shown above.

4) Why the correct answer is correct
- The correct option must include i, ii, and iv (true statements) and exclude iii (false). That precisely matches the properties described: one-way, used for passwords, and useful for integrity checks.

5) Why other options are incorrect
- A (i and ii only): omits iv which is true.
- B (ii and iii only): includes iii which is false and omits i and iv.
- C (All of the above): incorrectly includes iii as true.

6) Conclusion
- Therefore the correct choice is D. i, ii, and iv only — confirming the provided answer.

Which statements about hashing are correct? i. It is a one-way functionii. Used for password storageiii. Can be reversed with the correct keyiv. Ensures data integrity单项选择题

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