Module 2 challenge: Pelcgbybtl (Cryptology):IT Security: Defense against the digital dark arts(Google IT Support Professional Certificate) Answers:2025

Question 1

The logic used to convert plaintext into ciphertext is called a(n) ______.

✅ Encryption algorithm
❌ Integrity check
❌ Permutation
❌ Data protection standard

Explanation:
An encryption algorithm is the mathematical process that converts readable data (plaintext) into unreadable form (ciphertext) using a key.

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Question 2

How can you make a symmetric encryption key more difficult to break?

✅ Increase the length of the key.
❌ Use it fewer times
❌ Use an initialization vector
❌ Make the key smaller

Explanation:
A longer key increases the total number of possible combinations, making brute-force attacks exponentially harder.

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Question 3

Which of the following are necessary components for encryption and decryption operations when using an asymmetric encryption system?

✅ Private key
✅ Public key
❌ Digest
❌ Public key signature

Explanation:
Asymmetric encryption uses two keys:

• Public key (for encryption)

• Private key (for decryption).
  This pair ensures confidentiality and authenticity between sender and receiver.

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Question 4

In which scenarios is symmetric encryption better than asymmetric encryption?

✅ Encrypting and decrypting a large amount of data
✅ Communications over a trusted network
❌ Over untrusted networks
❌ When you need digital signatures

Explanation:
Symmetric encryption is faster and more efficient, so it’s ideal for large or internal data transfers where both parties can safely share a single secret key.

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Question 5

Which are true of an ideal hash function?

✅ Maps any amount of data to an output of fixed size
✅ A change in input is not correlated with the resulting change in output
✅ They are deterministic
❌ Can recover plaintext from hash

Explanation:
A hash function should:

• Always produce the same output for the same input (deterministic)

• Produce fixed-size outputs

• Be impossible to reverse

• Have outputs that look random even with small input changes (avalanche effect).

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Question 6

Why have experts recommended replacing SHA1 with SHA2 or SHA3?

✅ Attacking SHA1 hashes is expensive, but cost is decreasing
✅ A full hash collision of SHA1 has been published
✅ SHA1 collisions used to forge digital certificates
❌ Attacking SHA1 is easy and requires little power

Explanation:
SHA1 is deprecated because:

• Collisions are feasible with modern computing power

• Real-world certificate forgeries have occurred
  → SHA2/SHA3 provide stronger, collision-resistant hashing.

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Question 7

In TLS, a client validates a server’s certificate by checking that it:

✅ Is trusted
✅ Is for the correct host name
❌ Supports the correct TLS version
❌ Lists the shared secret

Explanation:
During the TLS handshake, the client verifies that:

• The certificate comes from a trusted Certificate Authority (CA)

• The certificate’s host name matches the domain being accessed.

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Question 8

____ is a system that defines the creation, storage, and distribution of digital certificates.

✅ PKI (Public Key Infrastructure)
❌ CA
❌ TLS
❌ VPN

Explanation:
PKI manages the entire lifecycle of digital certificates — creation, validation, and revocation — using Certificate Authorities (CAs) and registration authorities.

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Question 9

Using an asymmetric cryptosystem provides which benefits?

✅ Authenticity
✅ Confidentiality
✅ Non-repudiation
❌ Hashing

Explanation:
Asymmetric encryption ensures:

• Confidentiality (public key encrypts, private key decrypts)

• Authenticity (verifies sender identity)

• Non-repudiation (sender cannot deny sending a signed message).

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Question 10

How does AES GCM operate?

✅ It generates sequentially numbered ciphertext blocks by encrypting an incrementing counter.
❌ Combines multiple algorithms
❌ Uses chaining
❌ Fixed IV stream cipher

Explanation:
AES-GCM (Galois/Counter Mode) uses a counter mode to encrypt each block with a unique counter value, providing both confidentiality and integrity through built-in authentication tags.

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🧾 Summary Table

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