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ISC2 ISSAP Exam - Topic 1 Question 49 Discussion

Actual exam question for ISC2's ISSAP exam
Question #: 49
Topic #: 1
[All ISSAP Questions]

Which of the following encryption modes has the property to allow many error correcting codes to function normally even when applied before encryption?

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Suggested Answer: A

XORed with the plaintext blocks to get the ciphertext. With other stream ciphers, flipping a bit in the ciphertext produces a flipped bit in the

plaintext at the same location. This property allows many error correcting codes to function normally even when applied before encryption.

Answer option C is incorrect. In the cipher-block chaining (CBC) mode, each block of plaintext is XORed with the previous ciphertext block

before being encrypted.

Answer option D is incorrect. The propagating cipher-block chaining or plaintext cipher-block chaining (PCBC) mode is designed to cause small

changes in the ciphertext to propagate indefinitely when decrypting, as well as when encrypting.

Answer option B is incorrect. The cipher feedback (CFB) mode, a close relative of CBC, makes a block cipher into a self-synchronizing stream

cipher.


by Alecia at May 08, 2022, 02:28 AM

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Sylvie
4 months ago
PCBC mode is underrated, but I think OFB is the best choice here.
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Ilene
4 months ago
Wait, really? I didn't know OFB had that property!
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Lavera
4 months ago
I thought CFB was better for error correction?
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Roxanne
4 months ago
Totally agree, OFB is great for that!
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Lennie
5 months ago
OFB mode is the one that allows error correction codes to work well.
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Denny
5 months ago
PCBC mode sounds familiar, but I can't remember if it has the same properties as OFB. I should probably go with my gut on this one.
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Sanjuana
5 months ago
I feel like CBC mode is commonly mentioned in discussions about error correction, but I can't recall if it actually allows for normal function with codes.
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Jettie
5 months ago
I remember practicing a question about CFB mode, and I think it had some issues with error propagation, so I don't think it's the right answer.
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Linn
5 months ago
I think it might be OFB mode since it processes data in a way that doesn't propagate errors, but I'm not entirely sure.
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Anjelica
5 months ago
I think the key here is to focus on the core capabilities of the EFM standard, which are monitoring and troubleshooting point-to-point links and the last-mile connection. Options A and E seem to capture that best.
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Paz
5 months ago
I think the key is to identify the specific match criteria that determine which packets get the higher priority. The options mention dotlp and dscp, so I'll need to check how those are defined in the policy.
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