To protect passwords in the case when an attacker obtains the password database, _______ is used to prevent _________ of the passwords.

Question

BlackTom AI · Accepted Answer

Hashing is a one-way function: once a password is hashed, you cannot feasibly recover the original plaintext by "decrypting" the hash.

1) Relevant knowledge points and concepts
- Hashing: deterministic, one-way function that maps input to fixed-size output; not reversible. Common password hashes: bcrypt, Argon2, PBKDF2, scrypt.
- Encryption: reversible transformation using keys; ciphertext can be decrypted if the key is obtained.
- Password storage best practice: store salted, slow hashes so attackers cannot recover plaintexts even if database is leaked.
- Verification workflow: user supplies password, system hashes it and compares to stored hash.

2) Step-by-step reasoning process
- If an attacker obtains the password database, they typically obtain stored values (hashes or ciphertexts).
- If passwords are encrypted (not hashed), the attacker could decrypt them if they obtain the decryption key.
- If passwords are hashed, there is no decryption operation; attacker must perform guessing/brute-force (hash candidate and compare), which is mitigated by salts and slow hashing.
- Therefore, hashing is used to prevent decryption of passwords (i.e., to avoid having a reversible form attackers can decrypt).

3) Intermediate steps (storage and verification)
- Registration: P (plaintext password) -> H = hash(P + salt) -> store H, salt.
- Login: user enters P' -> compute H' = hash(P' + stored salt) -> compare H' to stored H; accept if equal.
- No decryption step exists because H does not contain a reversible ciphertext.

4) Why the correct answer is correct
- Hashing prevents attackers from decrypting stored values because hashes are not reversible; encryption would allow decryption if keys are compromised.

5) Why other options are incorrect
- "decryption, hashing": nonsense order; decryption does not protect against hashing.
- "encryption, hashing": encryption is reversible; it does not inherently prevent recovery if keys are compromised.
- "hashing, encryption": hashing does not prevent encryption; the phrase is reversed in meaning.

6) Conclusion
Hashing is used to prevent decryption of the passwords — matching the provided correct answer: "hashing, decryption."

To protect passwords in the case when an attacker obtains the password database, _ is used to prevent ___ of the passwords.单项选择题

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To protect passwords in the case when an attacker obtains the password database, _______ is used to prevent _________ of the passwords.单项选择题