Cryptography Concepts

Section A - Concepts

• A threat is defined best as an event with the potential to adversely impact the security properties of information systems
• The best example of a passive attack involves an attacker exploiting system vulnerability to view bank balances
• CIA acronym stands for Confidentiality, Integrity, Availability
• RSA uses two different keys for both encryption and decryption
• According to Claude Shannon, the key is the most important thing to keep secret
• Transposition cipher reorders each character to form the ciphertext
• String of alphabetic characters cannot be chosen as a key for Caesar cipher
• DES is one of the modern cryptography algorithms that is the most vulnerable to brute-forcing attacks
• It's easy to see the relationship between plaintext and ciphertext is the best reason to avoid using Electronic Code Book (ECB) mode of operation
• Third party making a copy of a key sent between communicating parties is the main problem solved by the Diffie-Hellman method
• A false property for a hash function is different output for the same input
• Rainbow table is best defined as a dictionary of hashes
• Password salting is used to increase the work required to brute force a password
• A password like "apple" is easy for humans to remember and easy for computers to guess using dictionary attacks
• Password spraying is using the same password on many different accounts
• A smart card is best described as "something you possess"
• When an enrolled user presents a biometric to an authentication system and it doesn't recognise them, it's called a "False non-match"
• The initial action a virus performs involves checking whether a condition is met that enables it to find a program to infect
• Web shell's primary function is to maintain access
• A system is safe from a zero-day exploit once the vulnerability is fixed
• The most important requirement for a switched packet network is the delivery of packets
• Including a source port identifies which program on client will process the reply
• With a shared key in a WPA2 network, it is false to say that you can protect your web traffic from sniffing using HTTPS
• A digital certificate does not contain the owner's private key
• For a MITM attack using an evil twin, it is LEAST important that the evil twin implements a captive portal

Section B - Applying Concepts

• Being guilty because the action is more important than intention is the correct statement regarding guilt
• Encrypting the plaintext MAXY with the Vigenere cipher and a key of BZ yields the ciphertext NZYX
• Using a cipher with a block size of 16 bits requires 9 bits to be added as padding for a 151-bit plaintext
• If Alice is using RSA to authenticate that she encrypted a message, she should use Alice’s private key

Section C - Short Answers

• Credential stuffing attack: Attacker obtains usernames and passwords then test stolen credentials and gains access if credentials reused, use password per site and some form of SSO
• Hash-based tokens and authenticators using a one-time-password need to have the counter synchronised with each other, since there is no direct communication between the token and the authenticator
• Post quantum computing reduces the time to do number factorisation that is the basis of asymmetric crypto, this allows uses of code that is hard to solve that don't rely on factorising and cannot easily be solved using quantum algorithms