Scenario:Passwords are stored in a database as hashes. Even if the database is compromised, original passwords cannot be recovered. Question: Which cryptographic concept is applied?

Question

BlackTom AI · Accepted Answer

Irreversible hashing (one‑way hashing) stores a fixed-size digest of the password such that the original password cannot be recovered from the digest.

1) Relevant knowledge points and concepts
- Hash functions: deterministic algorithms that map arbitrary-length input to fixed-size outputs (digests).
- One-way (irreversible) property / preimage resistance: given a digest, it is computationally infeasible to find an input that maps to it.
- Collision resistance: hard to find two different inputs with the same digest.
- Contrast to encryption: encryption is reversible (requires a key to decrypt), signatures provide authenticity, and symmetric key sharing concerns key management for reversible encryption.

2) Step-by-step reasoning
- The scenario: passwords are stored as hashes; even if the database is compromised, original passwords cannot be recovered.
- This directly describes a one-way transformation: storage of non-reversible digests so verification is by hashing the candidate password and comparing digests.
- Therefore the cryptographic concept is an irreversible (one-way) hash function.

3) Calculations / intermediate steps
- No numeric calculation is required. The logical mapping is: stored value = H(password). Verification: H(supplied_password) ?= stored_value. No decryption step exists, confirming irreversibility.

4) Why the correct answer is correct
- Irreversible hashing matches the described properties: non-recoverability of original passwords and use of hash digests for verification. This is standard practice (often with salts and slow hash functions like bcrypt/scrypt/Argon2).

5) Why other options are incorrect
- a. Reversible encryption: would allow recovery of the original password using a key — contradicts “cannot be recovered.”
- b. Digital signature: used to prove authenticity/integrity, not for storing passwords that can’t be reversed.
- c. Symmetric key sharing: relates to sharing keys for reversible encryption, not to storing non-recoverable password digests.

6) Conclusion
The correct concept is d. Irreversible hashing, which matches the provided answer.

Scenario:Passwords are stored in a database as hashes. Even if the database is compromised, original passwords cannot be recovered. Question: Which cryptographic concept is applied?单项选择题

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