Cryptography Quiz: Transposition Ciphers and RSA

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Questions and Answers

Which type of encryption is the affine cipher?

Shift cipher

Symmetric encryption

Transposition cipher

Asymmetric encryption (correct)

What is the purpose of the salts in password storage?

To generate the hash of the password

To speed up the efficiency of the dictionary attacks

To slow down the efficiency of the dictionary attacks (correct)

To store the password securely

What is the key generation algorithm of a transposition cipher?

Generating a random permutation bit by bit

Using the same permutation as the encryption algorithm

Applying the permutation to the whole alphabet

Generating all permutations of (1,...,n) where n is the length of a block (correct)

What is the purpose of the Message Authentication Code?

To verify the integrity of the data Signup and view all the answers

What is the notion of authentication?

Encompasses identity verification, message origin integrity and message content integrity Signup and view all the answers

What is the input of the asymmetric key generation algorithm?

Security parameter Signup and view all the answers

What type of cipher is the affine cipher a special case of?

Shift cipher Signup and view all the answers

What type of attacks is slowed down by applying salts in password storage?

Dictionary attacks Signup and view all the answers

What is the size of the key space for transposition ciphers?

n! Signup and view all the answers

Is it proven that the RSA problem is as hard as prime factorization?

No Signup and view all the answers

What is secret in the RSA algorithm?

decryption exponent that is relatively prime to phi(n), where n is a modulus Signup and view all the answers

What is the role of the PKI Registration Authority?

Authenticating users Signup and view all the answers

Which statement is true about message authentication codes?

They prove the integrity of the messages Signup and view all the answers

What is the role of the PKI Certificate Authority?

Signing certificates Signup and view all the answers

Which of the following is a characteristic of the textbook RSA encryption scheme?

It has been successfully attacked Signup and view all the answers

What is the size of the typical RSA modulus today?

4096 bits Signup and view all the answers

What is the main goal of digital certificates?

To bind the owner with their public key Signup and view all the answers

What is the purpose of Risk Analysis?

To identify what to protect, whom, and define risks Signup and view all the answers

What type of attack involves sending a message back to the sender?

Replay attack Signup and view all the answers

What does a valid message authentication code prove?

Integrity Signup and view all the answers

What type of cipher is an affine cipher?

Substitution cipher Signup and view all the answers

Which type of encryption algorithm is used in RSA?

Asymmetric encryption algorithm Signup and view all the answers

What is the purpose of message authentication codes?

To ensure integrity and authenticity Signup and view all the answers

What is the purpose of administrative control?

To define security policies and procedures Signup and view all the answers

Study Notes

Transposition Ciphers

Apply permutations taken over the whole alphabet
Key generation algorithm generates all permutations of (1,…,n), where n is the length of a block
Key space size is n!, where n is the length of a block

RSA Algorithm

RSA problem is not proven to be as hard as prime factorization
Modular exponentiation, where the modulus is the product of two large primes with equal size, is a one-way function
Calculating the RSA decryption exponent out of the public key is as hard as factoring the modulus
Secret in case of the RSA algorithm: decryption exponent that is relatively prime to phi(n), where n is a modulus

RSA Key Generation

Input of asymmetric key generation algorithm: security parameter

PKI

Registration Authority: authenticating users, storing the revocation list
Certificate Authority: revoking certificates, generating key pairs, signing certificates, registering certificate requests

Message Authentication Codes

Suitable for entity authentication
Valid message authentication code proves the integrity of the messages and non-repudiation of the messages
Not suitable for providing confidentiality

Affine Cipher

Decryption key calculation: Extended Euclidean Algorithm might be applied
Asymmetric encryption, with different encryption and decryption keys
Special case of the shift ciphers

Ransomware

Saves files and returns them after receiving the ransom
Locks you out of your computer

Chernobyl Virus

Deletes data

Authentication

Notion of authentication: data is not altered in an unauthorized manner, encompasses identity verification, message origin integrity, and message content integrity

Message Authentication Code

Used to verify the integrity of the data and the rightness of the data

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Description

This quiz covers the basics of transposition ciphers, key generation, and the relationship between the RSA problem and prime factorization.