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Exam CISSP topic 1 question 79 discussion

Actual exam question from ISC's CISSP
Question #: 79
Topic #: 1
[All CISSP Questions]

Which technique can be used to make an encryption scheme more resistant to a known plaintext attack?

  • A. Hashing the data before encryption
  • B. Hashing the data after encryption
  • C. Compressing the data after encryption
  • D. Compressing the data before encryption
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Suggested Answer: D 🗳️

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nohup
Highly Voted 1 year, 2 months ago
Should it not be compressing data before encryption? Has is one way and hence recipent may not be able to decrypt it
upvoted 12 times
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kabwitte
Highly Voted 10 months, 4 weeks ago
D is the correct answer. Compression relies on patterns. When data is encrypted properly, there should be no patterns at all. As a result, since compression relies on patterns, one will NOT be able to compress data after it is encrypted (no patterns). If you compress the data before you encrypt, then there will be patterns to compress.
upvoted 7 times
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shhi
Most Recent 1 week, 2 days ago
Selected Answer: A
A Sender always hashes data first then encrypts it then sends to a receiver.
upvoted 1 times
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paddi
4 months, 3 weeks ago
I strongly go with A.
upvoted 1 times
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mamun07
5 months, 2 weeks ago
Answer is C. Known plaintext attack means the attacked has the cipher text and the plaintext and from that he can look for patterns. If the data is compressed first and then encrypted, then the only pattern the attacker can come with is the patter co-relation between the compressed text and the cipher text. If the data is encrypted first and then compressed, then the attacker simply needs to decompress and he only has to perform the known-plaintext attack.
upvoted 1 times
mamun07
5 months, 2 weeks ago
Sorry for the typo. The answer is D
upvoted 1 times
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Ariel235788
6 months, 1 week ago
compressing data changes the data on a binary level. then encrypting the compressed data makes it more secure. if you change data at the binary level, itll be harder to attack with a known plaintext since the plaintext has been compressed
upvoted 1 times
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SKYDIVEDXB
7 months, 1 week ago
"A" is my answer
upvoted 1 times
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samir2020
7 months, 2 weeks ago
Known plaintext attack: This type of attack requires the attacker to have the plaintext and ciphertext of one or more messages. Encrypted file archives such as zip are prone to this type of attack.
upvoted 1 times
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dotmt
7 months, 4 weeks ago
D ... https://stackoverflow.com/questions/4399812/is-it-better-to-encrypt-a-message-and-then-compress-it-or-the-other-way-around
upvoted 1 times
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asdasdfsd
8 months ago
A cannot possibly be the answer. If you hash something you lose the information... and it is impossible to compress ciphertext so it has to be D
upvoted 1 times
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Neela
8 months, 1 week ago
Answer is A - By using a combination of both encryption and hashing, security can be dramatically increased. For example, using HTTPS, which is encrypted, will ensure that a password sent over the internet is not read by someone watching the connection and using a hash to store the password in the database will ensure any break-ins will not present further compromises(due to password reuse, etc).
upvoted 3 times
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Alejandroalh
8 months, 3 weeks ago
I bet on A. The question is asking about an encryption scheme. You will send both the data and the hash to the receiver. Any comments on this?
upvoted 2 times
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Pealvare
9 months, 3 weeks ago
Encryption is a two-way function; what is encrypted can be decrypted with the proper key. Hashing, however, is a one-way function that scrambles plain text to produce a unique message digest. With a properly designed algorithm, there is no way to reverse the hashing process to reveal the original password.
upvoted 2 times
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madcloud
10 months ago
After looking around on multiple websites, it seems that compressing then encrypting is the way to go. D is correct
upvoted 3 times
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DigitalDanny
10 months, 2 weeks ago
Can someone tell me why not choosing A - Hashing?
upvoted 3 times
111ssy
10 months, 2 weeks ago
You can't decrypt hashing since it's one way.
upvoted 4 times
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Puri232
11 months, 1 week ago
B is correct
upvoted 1 times
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Ramnik
12 months ago
D is the correct answer.
upvoted 1 times
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A (35%)
C (25%)
B (20%)
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