Computer Security Questions and Answers

Answer: C

Correct answer: Needed

The check consists of comparing the fingerprint sent with the fingerprint computed from the document received, so both are required. Either one alone proves nothing.

Answer: B

Correct answer: Message Integrity

Integrity is the guarantee that the message arrives exactly as it was sent, with no bit altered. Confidentiality is a separate guarantee, that nobody else can read it.

Answer: C

Correct answer: kept secret

If the digest travelled openly alongside the message, an attacker could alter the message and recompute the digest to match. The digest must therefore be protected - kept secret, encrypted, or bound to a key - or the whole check is worthless.

Answer: A

Correct answer: Secret

The same reason: a digest an attacker can replace gives no protection, since the altered message would carry a correctly computed digest. Keeping it secret, or computing it with a secret key, is what makes the check meaningful.

Answer: A

Correct answer: 512 Bit Blocks

SHA-1 pads the message and processes it in 512-bit blocks, updating a running state, and emits a 160-bit digest at the end. The block size and the digest size are different numbers and are often confused.

Answer: B

Correct answer: Confidentiality

Confidentiality, or privacy, is exactly the expectation that nobody but the intended receiver can read the message. Integrity, authentication and nonrepudiation are the other three services and answer different questions.

Answer: C

Correct answer: Receiver site

Encryption happens where the message originates and decryption where it is read, so the message is in ciphertext for the whole of its journey. That is what protects it in transit.

Answer: D

Correct answer: Worm

A worm is self-contained: it propagates across a network on its own and needs no host program to attach to. Viruses and trojans both require something to carry them, and a trap door is a hidden entry point in a program rather than a program in its own right.

Answer: D

Correct answer: All of these

Norton, K7 and Quick Heal are all antivirus products.

Answer: C

Correct answer: Spam

Hackers, viruses and worms each threaten security directly. Spam is unsolicited advertising - a nuisance, and often the vehicle for the others, but not in itself a security threat.