30 Questions
What term is used for the original message before encryption?
Plaintext
Which encryption type was the only one in use before the introduction of asymmetric encryption?
Symmetric encryption
What is the term for the study of principles/methods of deciphering ciphertext without knowing the key?
Cryptology
Who first publicly proposed Public-key encryption?
Diffie and Hellman
What does cryptanalysis involve?
Deciphering ciphertext without the key
What does encipher refer to in cryptography?
Converting plaintext to ciphertext
What is a characteristic of the Vigenère cipher?
Requires a 26x26 table with letters A to Z
What is the purpose of repeating the keyword in the Vigenère cipher?
To match the length of the plaintext
Who invented the Playfair Cipher?
Charles Wheatstone
What is the key matrix in the Playfair Cipher based on?
A keyword without duplicates
How does the Playfair Cipher handle repeated letters in encryption?
It replaces repeated letters with filler like 'X'
Which cipher is known for encrypting multiple letters at once to improve security?
Playfair Cipher
What is the main difference between public-key cryptography and symmetric key encryption?
Public-key cryptography uses two separate keys while symmetric key encryption uses only one key.
Which of the following is NOT a consequence of using two keys in public-key cryptography?
Decreased key security
What is the general goal of cryptanalytic attacks?
To recover the encrypted message
How does a brute-force attack differ from a cryptanalytic attack?
A brute-force attack tries every possible key until an intelligible translation is obtained, while a cryptanalytic attack relies on algorithm characteristics.
What factor determines the time required for a brute-force attack?
The number of alternative keys available
How does the time required for a brute-force attack change with an increase in key size?
The time required increases exponentially with the key size.
What is the mathematical representation of the Caesar cipher transformation?
c = E(p) = (p + k) mod (26)
What is the main disadvantage of the Caesar cipher in terms of security?
It has only 25 possible keys
In cryptanalysis of the Caesar cipher, what method can be used to decode the ciphertext?
Brute force search
What technique involves replacing plaintext letters with other letters, numbers, or symbols?
Classical substitution cipher
How many characters are there in a permutation of a finite set of elements?
26
What transformation replaces each letter with the 3rd letter that follows it in the alphabet?
Caesar cipher
How many permutations are there for a set with elements {a, b, c}?
6 permutations
What does a monoalphabetic cipher do?
Maps each plaintext letter to a random ciphertext letter
Why is it incorrect to assume that a monoalphabetic cipher with 26! keys is secure?
Language characteristics and redundancy make decryption easy
What is one of the reasons why English text is vulnerable to cryptanalysis?
The absence of common letters like E, T, R, N in English
In the given ciphertext 'UZQSOVUOHXMOPVGPOZPEVSGZWSZOPFPESXUDBMETSXAIZ', what letters are most likely to represent 'e' and 't'?
'P' and 'Z'
What is the main challenge faced in cryptanalysis when analyzing the given ciphertext?
Dealing with language characteristics like letter frequencies and redundancy
Test your knowledge on classical encryption techniques used in the field of cryptography. Learn about the basic terminology such as plaintext, ciphertext, cipher, and key. Explore how encryption has been historically used in war and military communications.
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