CAP Cryptography & Encryption 2

Question 1

Which cryptographic concept ensures that a sender cannot later deny having sent a message?

Accepted Answer

Non-repudiation

Answer

Non-repudiation, typically achieved via digital signatures, prevents a sender from falsely denying they originated a message.

Question 2

In the context of PKI, what is the role of a Certificate Revocation List (CRL)?

Accepted Answer

It identifies certificates that have been invalidated before their expiration date

Answer

A CRL is a list published by a Certificate Authority that identifies certificates that have been revoked prior to their scheduled expiration.

Question 3

Which key exchange protocol allows two parties to securely establish a shared secret over an insecure channel without prior shared secrets?

Accepted Answer

Diffie-Hellman

Answer

Diffie-Hellman key exchange enables two parties to derive a shared secret over a public channel without previously sharing any secret material.

Question 4

What distinguishes a stream cipher from a block cipher?

Accepted Answer

Stream ciphers encrypt one bit or byte at a time; block ciphers encrypt fixed-size chunks

Answer

Stream ciphers process plaintext one bit or byte at a time using a keystream, whereas block ciphers encrypt data in fixed-size blocks.

Question 5

Which FIPS standard specifies the Advanced Encryption Standard (AES)?

Accepted Answer

FIPS 197

Answer

FIPS 197 formally specifies AES, which supports key lengths of 128, 192, and 256 bits.

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