attacks

Question 1

cipher cracking methodology that involves identifying patterns and variations in the probability of codes.
i.e. a three-letter ciphered text combination spotted at the beginning of a string too often could tip us off that those three letters correlate the letters THE in the English alphabet.

Answer 1

Frequency Analysis

Question 2

Why should Diffie-Hellman not be used? What should we use instead?

Answer 2

It is vulnerable to man in the middle and downgrade attacks. Use PKI and ephemeral keys instead.

Question 3

Which symmetric stream is resistant to timing attacks?

Answer 3

ChaCha

Question 4

NOBUS

Answer 4

(‘nobody but us’) backdoor. This is where it is mathematically possible for government agents to crack the encryption, but no-one else can

Question 5

Key escrow.

Answer 5

This is where a copy of the encryption key is kept in escrow so that it can be used by a government agent

Question 6

Where the intruder uses brute force to decrypt the ciphertext and tries every possible key.

Answer 6

Exhaustive search

Question 7

Known plaintext attack.

Answer 7

Where the intruder knows part of the ciphertext and the corresponding plaintext.

The known ciphertext and plaintext can then be used to decrypt the rest of the ciphertext.

Question 8

Where the intruder sends a message to the target, this is then encrypted with the target’s private-key and the intruder then analyses the encrypted message.

For example, an intruder may send an e-mail to the encryption file server and the intruder spies on the delivered message.

Answer 8

Chosen-ciphertext.

Question 9

Where the intruder inserts or modifies messages.

Answer 9

Active attack

Question 10

Where the intruder takes a legitimate message and sends it into the network at some future time.

Answer 10

The replay system

Question 11

Where the intruder mixes parts of two different encrypted messages and is able to create a new message. This message is likely to make no sense but may trick the receiver into doing something that helps the intruder.

Answer 11

Cut-and-paste.

Question 12

Some encryption schemes use the time of the computer to create the key. Resetting this time or determining the time that the message was created can give some useful information to the intruder.

Answer 12

Time resetting.

Question 13

Diffie-Helman handshakes are vulnerable to what?

Answer 13

MiTM

Question 14

side path attack?

Answer 14

.

Question 15

What three things is AES vulnerable to?

Answer 15

AES has proven to be free from major vulnerabilities, but poor implementation of the encryption method leaves it susceptible to attacks such as:
Brute force, use of Non-Random Numbers, and copy-and-paste.

Question 16

Difference between Time attack and Time resetting?

Answer 16

Time attack - analyzing the amount of time needed for decryption to calculate the key.

Time resetting - Changing or observing the local time on a device to foil certain encryption schemes.

Question 17

What is RSA vulnerable to?

Answer 17

RSA suffers from several weaknesses and is susceptible to numerous attacks and cracking methods including factorization of prime numbers used within the algorithm.

Question 18

What addresses the problems of brute forcing an MD5 hash?

Answer 18

The APR1 format combats this by iterating the hash value 1,000 times and salting the value.

Question 19

What addresses the problems of brute forcing an MD5 hash?

Answer 19

The Apache-defined APR1 format combats this by iterating the hash value 1,000 times and salting the value.

Question 20

Looks for a rollover of the same value for an IV

Answer 20

Replay attack

Question 21

Which encryption algorithm did the National Institute of Standards and Technology (NIST) designate as a specification for the encryption of electronic information?

Answer 21

AES

Question 22

Which type of cipher is ChaCha?

Answer 22

stream

Question 23

What is SHA hashed stored passwords vulnerable to and why?

Answer 23

SHA method has for storing passwords does not have a salt making it open to rainbow table attacks and brute force.

Question 24

This is where part of the message has some significance to the original and generates the same hash signature. This is defined as a Pre-image attack.

Answer 24

Similar context.

Question 25

This is where an alternative message is created with the same hash signature and has a direct relation to the original message. This is an extension to a Pre-image attack.

Answer 25

Full context.

Question 26

Methods to combat DHE_EXPORT Downgrade attacks on Diffie Hellman include:

Answer 26

Disabling Export Cipher Suites
Using (Ephemeral) Elliptic-Curve Diffie-Hellman (ECDHE)
Use a strong group.

Question 27

A weakness discovered in Diffie Hellman is that it is…

Answer 27

fairly easy to precompute on values for two popular Diffie-Hellman parameters (which use the DHE_EXPORT cipher set).

Question 28

a method of attacking/discovering polyalphabetic substitution keywords

Answer 28

Kasiski examnation

Question 29

the attacker has an access to the ciphertext and its corresponding plaintext

Answer 29

known-plaintext attack

Question 30

difference between MiTM and active attack?

Answer 30

active attack - attacker interfering between two parties and sometimes intercepting or modifying data in the communication stream

MiTM - attacker impersonating both parties involved in a communication stream

Question 31

copy-paste attack mitigation for AES?

Answer 31

OFB loop

Question 32

differential vs linear analysis?

Answer 32

linear - finds similarities

differential - finds differences