Free Practice Quiz Question List

7 Cryptography in Secure Protocols Online Quiz Questions

Use this free practice quiz with 20 questions to review 7 Cryptography in Secure Protocols, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

True or false: A plain hash digest, by itself, proves that the data was created by a particular person.

A
True
B
False

Choose one

1 point

A client receives a CA-signed certificate for a server. Which role does the certificate serve?

A
It contains the server's private key and encrypts application data.
B
It connects a public key to identity information through a CA-signed certificate.
C
It derives traffic keys from a shared secret.
D
It encrypts each message and detects tampering.

Fill in the blank

1 point

With authenticated encryption with associated data (AEAD), associated data is but remains visible.

Written response

1 point

After key agreement produces shared secret material, what kind of mechanism turns it into separate, appropriately sized keys?

Choose one

1 point

An SSH client reports that a server's host key has unexpectedly changed. What is the main risk of accepting the new key without checking it?

A
It guarantees that the host's key has been signed by a public certificate authority.
B
It replaces key exchange, so the parties no longer need session keys.
C
It can defeat server authentication by allowing an impostor host to be accepted.
D
It only affects whether the connection uses AEAD, not whether the server is authenticated.

Choose one

1 point

A service encrypts many messages using AEAD. Which practice best follows the stated security principles?

A
Reuse the same nonce with a key so peers can recognize the session.
B
Do not reuse a nonce with the same AEAD key.
C
Publish the AEAD key alongside the ciphertext.
D
Use associated data to make the ciphertext confidential.

Choose one

1 point

Which sequence best describes the common design pattern for a secure protocol?

A
Agree on secret material → protect each message with AEAD → authenticate public keys → derive traffic keys
B
Derive traffic keys → authenticate public keys → protect each message with AEAD → agree on secret material
C
Authenticate public keys → agree on secret material → derive traffic keys → protect each message with AEAD
D
Protect each message with AEAD → derive traffic keys → agree on secret material → authenticate public keys

Written response

1 point

Name one method a messaging user can use to authenticate another person's identity key.

True or false

1 point

True or false: In a protocol using ephemeral Diffie–Hellman, later compromise of a long-term certificate-signing key does not by itself reveal previously recorded session traffic, assuming ephemeral secrets were securely erased.

A
True
B
False

Choose all

1 point

In a typical TLS 1.3 handshake, select all statements that correctly describe what these checks establish.

A
Certificate validation connects the server's key to its claimed identity.
B
CertificateVerify proves possession of the corresponding private key and binds that proof to the handshake.
C
Finished confirms that the peer has the same handshake state and keys.
D
The certificate chain encrypts all application records.
E
CertificateVerify derives the application traffic keys from the shared secret.

Fill in the blank

1 point

In MLS, a membership change advances the group to a new with new key material.

Choose all

1 point

Select all statements that accurately describe the Double Ratchet.

A
Each message uses a distinct message key.
B
Fresh secret input can enable recovery from some key compromises.
C
The protocol remains secure if ratchet state is lost or incorrectly updated.
D
The ratchet combines symmetric-key chains with new Diffie–Hellman contributions.

Choose one

1 point

How does X3DH help when a messaging recipient is offline?

A
It requires both users to be online at the same time and sends the shared secret directly.
B
It lets a sender use the recipient's published identity and prekeys to establish shared secret material asynchronously.
C
It replaces identity-key authentication because prekeys prove who owns the recipient's identity key.
D
It uses a CA-signed certificate to encrypt every message sent afterward.

Open ended

1 point

Explain how TLS's protection goal differs from the goal of end-to-end messaging. Include one important limitation that applies to both.

True or false

1 point

True or false: X3DH can let a sender establish shared secret material with a recipient who is offline.

A
True
B
False

Choose one

1 point

Which statement best describes what a plain hash function provides in a secure protocol?

A
It encrypts the data so only the intended recipient can read it.
B
It maps the data to a fixed-length digest, but does not by itself prove who created the data.
C
It proves the sender’s identity whenever the digest is shared.
D
It creates a shared secret between two parties over a public channel.

Written response

1 point

In a PKI certificate, what type of key is included alongside identity information? Enter the key type, not a key value.

Choose one

1 point

A protocol supplies a message label as associated data to an AEAD operation. Which property should the protocol expect for that label?

A
It is encrypted but not authenticated.
B
It is hidden from observers and is not checked for tampering.
C
It is authenticated but remains visible.
D
It replaces the need for a key-derivation function.

Written response

1 point

What algorithm combines symmetric-key chains with new Diffie–Hellman contributions to derive fresh message keys over time? Enter the algorithm name.

Choose one

1 point

In a typical TLS 1.3 handshake, what does the server’s CertificateVerify signature establish?

A
It confirms that the browser trusts the certificate authority without checking the server name.
B
It proves possession of the private key corresponding to the certificate and binds the proof to the handshake.
C
It encrypts application records using the certificate’s public key.
D
It derives distinct application traffic keys from the shared secret.