Free Practice Quiz Question List

4 Public-Key Cryptography and Digital Signatures Online Quiz Questions

Use this free practice quiz with 20 questions to review 4 Public-Key Cryptography and Digital Signatures, test your knowledge, and prepare for your next test or exam.

20 questions

True or false

1 point

True or false: Using fresh ephemeral key-agreement values can help limit the damage if a long-term key is later compromised.

A
True
B
False

True or false

1 point

True or false: A key exchange by itself proves the identity of the party on the other end.

A
True
B
False

Fill in the blank

1 point

When a signature algorithm incorporates hashing, changing the signed message should cause to fail.

Fill in the blank

1 point

Although a public key and its private key are mathematically related, deriving the private key from the public key should be .

Written response

1 point

What is the process called in which parties obtain shared secret material for later cryptographic use?

Written response

1 point

What is the name of the approach in which one party generates secret key material and securely sends it using the recipient’s public key or a key-encapsulation mechanism?

Choose one

1 point

A sender needs to protect a large amount of data for a recipient. Which approach describes hybrid encryption?

A
It encrypts all the data directly with the recipient’s public key, avoiding symmetric encryption.
B
It encrypts the data with a fresh symmetric key and uses a public-key mechanism to protect or establish that key.
C
It signs the data with the recipient’s private key so the sender can decrypt it.
D
It uses a public key to derive the recipient’s private key, then encrypts the data symmetrically.

Choose one

1 point

Alex wants to send Priya a confidential message using public-key encryption. Which key use is appropriate?

A
Alex’s private key encrypts the message, and Priya’s public key decrypts it.
B
Priya’s private key encrypts the message, and Alex’s private key decrypts it.
C
Priya’s public key encrypts the message, and Priya’s private key decrypts it.
D
Alex’s public key encrypts the message, and Priya’s public key decrypts it.

Choose one

1 point

A verifier has checked that a signature is mathematically valid but needs to establish the signer’s real-world identity. What is needed to bind the public key to that identity?

A
A valid certificate and a trusted certification path that bind the key to the identity.
B
A valid signature, even if the public key is not associated with a trusted identity.
C
The fact that the public key is mathematically related to a private key.
D
The fact that the message is readable by anyone who has the public key.

Choose one

1 point

A team has a key pair intended for signing. Which conclusion should guide its use in another cryptographic operation?

A
A signing key pair is automatically suitable for encryption and key agreement because both keys are mathematically related.
B
A key pair should be used only for its intended purpose; a signing key pair is not automatically suitable for encryption or key agreement.
C
A public signing key can be used to derive a matching private encryption key.
D
A private signing key can be shared publicly whenever the corresponding public key is trusted.

Choose all

1 point

Select all statements that accurately describe key agreement such as Diffie–Hellman.

A
Each party combines its own private value with the other party’s public value.
B
One party sends the resulting shared secret directly over the network.
C
Both parties can independently derive the same shared secret.
D
Only one party contributes information; the other receives the secret itself.
E
A key-derivation function can turn the shared secret into keys suitable for later cryptographic use.

Choose all

1 point

Select all claims that a valid digital signature supports by itself.

A
It supports integrity by helping detect changes to the signed data.
B
It conceals the message from anyone who has the public key.
C
It supports authentication that someone controlling the corresponding private key produced the signature.
D
It proves the signer’s real-world identity without any trusted binding between the public key and that identity.
E
It guarantees legal non-repudiation in every context.

Open ended

1 point

Compare key agreement with key transport. Explain who contributes or generates the secret material in each approach, how the parties obtain it, and whether the shared secret itself is sent over the network.

Choose one

1 point

Alex wants to send Priya a confidential message using public-key encryption. Which key use allows Priya to decrypt the message?

A
Alex encrypts with Alex’s private key, and Priya decrypts with Alex’s public key.
B
Alex encrypts with Priya’s public key, and Priya decrypts with Priya’s private key.
C
Alex encrypts with Priya’s private key, and Priya decrypts with Priya’s public key.
D
Alex encrypts with Alex’s public key, and Priya decrypts with Priya’s private key.

True or false

1 point

A valid digital signature encrypts the signed message so that only the signer can read it.

A
True
B
False

Written response

1 point

What is the process called when both parties contribute information, such as Diffie–Hellman values, to derive the same shared secret?

Choose one

1 point

After two parties derive a shared secret through key agreement, what is the key-derivation function used for?

A
It derives keys suitable for later symmetric encryption and authentication from the shared secret.
B
It sends the shared secret to the other party so both parties can confirm they received it.
C
It converts the shared secret into the other party’s private key.
D
It certifies that the other party’s real-world identity is genuine.

Written response

1 point

What adjective describes fresh, temporary key-agreement values that can help limit damage if a long-term key is later compromised?

Choose one

1 point

A protocol has one party generate secret key material and securely send it using the recipient’s public key or a key-encapsulation mechanism. What kind of approach is this?

A
Both parties independently generate private values and combine them with each other’s public values.
B
One party generates secret key material and securely sends it using the recipient’s public key or a KEM.
C
Both parties send their private keys to a third party, which creates a shared secret.
D
One party publishes the secret key material so the recipient can retrieve it.

Choose one

1 point

A user verifies a software publisher’s signature and wants to conclude that the publisher’s real-world identity is known. What else is needed?

A
The message was encrypted, so only the named publisher could have read it.
B
The signature proves the signer’s legal identity without any other procedure.
C
A trustworthy binding between the public key and the publisher’s identity, such as a valid certificate and trusted certification path, is needed.
D
The public key can be trusted as belonging to the publisher merely because it verifies the signature.