A startup is building a secure messaging app. They need to provide end-to-end encryption, forward secrecy, and the ability to verify the identity of contacts. They have limited server resources and want to minimize the computational load on mobile clients. Which design should they choose?

Use a single static symmetric key shared among all users for message encryption.

Use RSA-4096 for both key exchange and message encryption, with certificates from a public CA.

Use the Signal Protocol: ECDH for key exchange, AES for message encryption, and a trust-on-first-use (TOFU) mechanism for identity verification.

Use a hash of the message as the encryption key and send the hash via a separate channel.

A security analyst suspects that an attacker is intercepting and modifying messages between two servers that use a pre-shared symmetric key. The analyst wants to detect this type of attack and prevent it from succeeding. Which measure should the analyst implement?

Use a hash of the message without a key and append it to the message.

Switch to a longer symmetric key to make brute-force attacks harder.

Encrypt the message with the attacker's public key to prevent interception.

Add a message authentication code (MAC) to each message using the shared key.

A government agency requires that all official documents be signed to ensure the sender cannot deny having issued them. The agency uses a public key infrastructure. What should the sender do to achieve non-repudiation?

Encrypt the document with the recipient's public key

Encrypt the document with the sender's private key

Hash the document and encrypt the hash with the recipient's public key

Sign the document with the sender's private key

What does a digital signature primarily provide?

Confidentiality of the message content

Authenticity and non-repudiation

A company is setting up a new encrypted communication channel between two servers. They need to ensure that the key exchange is resistant to man-in-the-middle attacks, but they cannot afford a full public key infrastructure (PKI) with a certificate authority. Which approach provides the best balance of security and cost?

Use RSA key exchange with self-signed certificates and trust on first use (TOFU).

Use Diffie-Hellman with pre-shared keys (PSK) that are exchanged out-of-band and used to authenticate the exchange.

Use a static symmetric key that is hard-coded in both servers.

Use unauthenticated Diffie-Hellman and rely on the secrecy of the derived key.

EC-CouncilNetwork Defense Essentials

Domain 6Objective 1

Cryptographic Techniques and Algorithms NDE Practice Questions (Page 2)

Part of the Cryptography, PKI, and Data Security domain, which makes up ~15% of our current practice bank.

39questions here

8free pages

6concepts

Questions 6–10

6expert · hard
A startup is building a secure messaging app. They need to provide end-to-end encryption, forward secrecy, and the ability to verify the identity of contacts. They have limited server resources and want to minimize the computational load on mobile clients. Which design should they choose?
Select an answer first
7application · medium
A security analyst suspects that an attacker is intercepting and modifying messages between two servers that use a pre-shared symmetric key. The analyst wants to detect this type of attack and prevent it from succeeding. Which measure should the analyst implement?
Select an answer first
8application · medium
A government agency requires that all official documents be signed to ensure the sender cannot deny having issued them. The agency uses a public key infrastructure. What should the sender do to achieve non-repudiation?
Select an answer first
9foundation · easy
What does a digital signature primarily provide?
Select an answer first
10expert · hard
A company is setting up a new encrypted communication channel between two servers. They need to ensure that the key exchange is resistant to man-in-the-middle attacks, but they cannot afford a full public key infrastructure (PKI) with a certificate authority. Which approach provides the best balance of security and cost?
Select an answer first

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