1. What does RSA stand for in RSA encryption?
a) Random Secure Algorithm
b) Rivest, Shamir, Adleman
c) Reliable Security Algorithm
d) Robust Secure Authentication
✅ Answer: b) Rivest, Shamir, Adleman
🔹 RSA is named after its inventors: Ron Rivest, Adi Shamir, and Leonard Adleman.
2. What type of encryption does RSA use?
a) Symmetric encryption
b) Asymmetric encryption
c) Hashing
d) Stream cipher
✅ Answer: b) Asymmetric encryption
🔹 RSA is an asymmetric encryption algorithm that uses a pair of keys (public and private) for encryption and decryption.
3. In RSA, which key is used for encrypting a message?
a) Private key
b) Public key
c) Both keys together
d) Any random key
✅ Answer: b) Public key
🔹 In RSA, the public key is used for encryption, while the private key is used for decryption.
4. What is the purpose of the private key in RSA encryption?
a) Encrypt messages
b) Decrypt messages
c) Generate random numbers
d) Store data securely
✅ Answer: b) Decrypt messages
🔹 Only the private key can decrypt messages encrypted with the corresponding public key.
5. What is the primary mathematical principle behind RSA encryption?
a) Elliptic Curve Cryptography
b) Large prime factorization
c) XOR operations
d) Modular addition
✅ Answer: b) Large prime factorization
🔹 RSA security relies on the difficulty of factoring large prime numbers.
6. Why is RSA considered secure?
a) It uses quantum mechanics
b) It uses symmetric encryption
c) Factoring large prime numbers is computationally difficult
d) It is based on hash functions
✅ Answer: c) Factoring large prime numbers is computationally difficult
🔹 Breaking RSA requires factoring the product of two large prime numbers, which is extremely difficult for classical computers.
7. Which algorithm is commonly used for generating RSA keys?
a) AES
b) Diffie-Hellman
c) Key Pair Generation Algorithm
d) The RSA key generation algorithm
✅ Answer: d) The RSA key generation algorithm
🔹 RSA key pairs are generated using the RSA algorithm by selecting two large prime numbers and computing their product.
8. Which of the following is NOT a component of an RSA key pair?
a) Modulus (n)
b) Public exponent (e)
c) Private exponent (d)
d) Symmetric key
✅ Answer: d) Symmetric key
🔹 RSA does not use symmetric keys; it uses a public and a private key for encryption and decryption.
9. If Alice wants to send an encrypted message to Bob using RSA, which key should she use?
a) Her own private key
b) Her own public key
c) Bob’s public key
d) Bob’s private key
✅ Answer: c) Bob’s public key
🔹 Alice encrypts the message using Bob’s public key so that only Bob can decrypt it with his private key.
10. In RSA, what does the modulus (n) represent?
a) The sum of two primes
b) The product of two primes
c) A random number
d) A hash value
✅ Answer: b) The product of two primes
🔹 The modulus (n) in RSA is the product of two large prime numbers, which forms the basis of RSA security.
11. What is the role of the public exponent (e) in RSA?
a) It is used to decrypt messages
b) It is part of the private key
c) It is used in the encryption process
d) It defines the key length
✅ Answer: c) It is used in the encryption process
🔹 The public exponent (e) is used to encrypt plaintext messages in RSA.
12. What is the recommended key length for RSA to be considered secure in 2025?
a) 512 bits
b) 1024 bits
c) 2048 bits
d) 128 bits
✅ Answer: c) 2048 bits
🔹 As of 2025, RSA keys of at least 2048 bits are recommended for secure encryption.
13. Why is a large key size required in RSA encryption?
a) To make encryption faster
b) To improve compression
c) To make factoring difficult
d) To reduce storage size
✅ Answer: c) To make factoring difficult
🔹 A larger key size increases security by making prime factorization infeasible for attackers.
14. What is the main disadvantage of RSA encryption?
a) It is slow for large data encryption
b) It is not secure
c) It requires a symmetric key
d) It cannot be used for digital signatures
✅ Answer: a) It is slow for large data encryption
🔹 RSA is computationally intensive, which makes it slow for encrypting large amounts of data.
15. How does RSA ensure message integrity?
a) By encrypting messages twice
b) By using digital signatures
c) By using a symmetric key
d) By hashing the message
✅ Answer: b) By using digital signatures
🔹 Digital signatures use RSA to verify message integrity and authenticity.
16. Which attack is RSA particularly vulnerable to if weak keys are used?
a) SQL Injection
b) Side-channel attacks
c) Brute force
d) Factorization attacks
✅ Answer: d) Factorization attacks
🔹 If RSA keys are too small, attackers can factorize the modulus and derive the private key.
17. What is the purpose of padding in RSA encryption?
a) To speed up encryption
b) To prevent certain types of attacks
c) To reduce key length
d) To add more keys
✅ Answer: b) To prevent certain types of attacks
🔹 Padding schemes (like OAEP) protect RSA encryption from attacks like chosen plaintext attacks.
18. Can RSA be used for both encryption and digital signatures?
a) Yes
b) No
✅ Answer: a) Yes
🔹 RSA can be used for encryption as well as for generating digital signatures.
19. What is the relationship between the private key and the public key?
a) They are identical
b) They are mathematically linked
c) They are interchangeable
d) They are randomly generated separately
✅ Answer: b) They are mathematically linked
🔹 The private key is derived mathematically from the same prime numbers used to generate the public key.
20. Which padding scheme is recommended for RSA encryption?
a) PKCS#1 v1.5
b) OAEP
c) ECB Mode
d) CBC Mode
✅ Answer: b) OAEP
🔹 Optimal Asymmetric Encryption Padding (OAEP) is recommended for RSA encryption as it provides better security.
21. What is the main reason RSA is slower compared to symmetric encryption algorithms?
a) RSA uses larger key sizes
b) RSA requires a shared secret key
c) RSA performs bitwise operations
d) RSA is designed for bulk encryption
✅ Answer: a) RSA uses larger key sizes
🔹 RSA encryption involves complex mathematical operations with large prime numbers, making it slower than symmetric encryption.
22. What is a common way to use RSA efficiently in secure communications?
a) Encrypt the entire message with RSA
b) Use RSA to encrypt a symmetric key
c) Use a single key for both encryption and decryption
d) Use RSA without key pairs
✅ Answer: b) Use RSA to encrypt a symmetric key
🔹 Most secure systems use RSA to encrypt a randomly generated symmetric key, which is then used for encrypting bulk data.
23. Which of the following is a potential weakness in RSA encryption?
a) Short key lengths
b) Use of symmetric keys
c) Lack of public key availability
d) Using different prime numbers
✅ Answer: a) Short key lengths
🔹 Using short RSA key lengths (e.g., 512-bit) makes it easier for attackers to factorize the modulus and break encryption.
24. What happens if an RSA private key is compromised?
a) It can be regenerated
b) All encrypted messages can be decrypted
c) The public key becomes invalid
d) Only signed messages are affected
✅ Answer: b) All encrypted messages can be decrypted
🔹 If the private key is exposed, an attacker can decrypt any past or future messages encrypted with the corresponding public key.
25. What is the recommended way to store an RSA private key securely?
a) Store it in a plain text file
b) Use a secure hardware module or key vault
c) Print it on paper and store it physically
d) Publish it alongside the public key
✅ Answer: b) Use a secure hardware module or key vault
🔹 Private keys should be stored in hardware security modules (HSMs) or secure vaults to prevent unauthorized access.
26. How does RSA protect against man-in-the-middle (MITM) attacks?
a) By using very large keys
b) By encrypting messages multiple times
c) By ensuring authenticity with digital signatures
d) By requiring symmetric encryption
✅ Answer: c) By ensuring authenticity with digital signatures
🔹 RSA digital signatures help verify the authenticity of messages, preventing MITM attacks.
27. Which cryptographic attack tries to derive the private key by analyzing ciphertexts?
a) Chosen-plaintext attack
b) Timing attack
c) Factorization attack
d) Dictionary attack
✅ Answer: c) Factorization attack
🔹 A factorization attack attempts to break RSA by factoring the modulus (n) into its prime components.
28. What does the term “key pair” mean in RSA encryption?
a) Two identical keys used for encryption and decryption
b) A public key and a private key that work together
c) A symmetric encryption key and a hashing key
d) A randomly generated encryption key and decryption key
✅ Answer: b) A public key and a private key that work together
🔹 RSA uses a mathematically related key pair: the public key for encryption and the private key for decryption.
29. Why is it difficult to reverse-engineer an RSA private key from the public key?
a) The public key is stored securely
b) The relationship between the keys is hidden
c) Prime factorization of large numbers is hard
d) The public key is frequently changed
✅ Answer: c) Prime factorization of large numbers is hard
🔹 RSA security is based on the computational difficulty of factoring large numbers into their prime components.
30. What does RSA encryption primarily secure in online communications?
a) Internet speed
b) Password storage
c) Confidentiality and authentication
d) File compression
✅ Answer: c) Confidentiality and authentication
🔹 RSA ensures that messages remain confidential and verifies the sender’s identity through digital signatures.
31. What is a typical public exponent (e) value in RSA encryption?
a) 2
b) 17
c) 65537
d) 1024
✅ Answer: c) 65537
🔹 65537 is commonly used because it provides a good balance between security and computational efficiency.
32. Which part of the RSA key is shared publicly?
a) Modulus (n) only
b) Public exponent (e) only
c) Both modulus (n) and public exponent (e)
d) Private exponent (d)
✅ Answer: c) Both modulus (n) and public exponent (e)
🔹 The public key consists of the modulus (n) and the public exponent (e), which are shared openly.
33. What is the process of verifying an RSA digital signature?
a) Encrypting the message with the sender’s private key
b) Decrypting the signature with the sender’s public key
c) Using a symmetric key to verify the signature
d) Hashing the message and matching it with the signature
✅ Answer: b) Decrypting the signature with the sender’s public key
🔹 To verify a digital signature, the receiver decrypts it using the sender’s public key and checks if it matches the expected hash.
34. Why is RSA not suitable for encrypting large amounts of data?
a) It lacks a secure key exchange mechanism
b) It has a slow encryption speed
c) It generates weak ciphertexts
d) It uses small key sizes
✅ Answer: b) It has a slow encryption speed
🔹 RSA is computationally expensive and is usually only used to encrypt small pieces of data, like symmetric encryption keys.
35. What does PKI (Public Key Infrastructure) use RSA for?
a) Encrypting private keys
b) Managing certificates and key distribution
c) Compressing digital data
d) Performing symmetric encryption
✅ Answer: b) Managing certificates and key distribution
🔹 PKI uses RSA for secure key exchanges and managing digital certificates for authentication.
36. What is the primary function of the RSA private exponent (d)?
a) Encrypting messages
b) Verifying digital signatures
c) Decrypting messages
d) Generating public keys
✅ Answer: c) Decrypting messages
🔹 The private exponent (d) is used in RSA to decrypt ciphertext encrypted with the public key.
37. What does OAEP stand for in RSA encryption?
a) Optimized Asymmetric Encryption Protocol
b) Optimal Asymmetric Encryption Padding
c) Overhead Asymmetric Encryption Protection
d) Open Authentication Encryption Process
✅ Answer: b) Optimal Asymmetric Encryption Padding
🔹 OAEP is a padding scheme used to enhance RSA security against certain cryptographic attacks.
38. Which of the following attacks can break weak RSA implementations?
a) Timing attacks
b) SQL Injection
c) Buffer overflow
d) Man-in-the-middle
✅ Answer: a) Timing attacks
🔹 Timing attacks can exploit variations in RSA computations to infer the private key.
39. What is the role of CRT (Chinese Remainder Theorem) in RSA?
a) It speeds up RSA decryption
b) It generates prime numbers
c) It secures key exchange
d) It prevents MITM attacks
✅ Answer: a) It speeds up RSA decryption
🔹 CRT optimizes RSA decryption by breaking operations into smaller, faster computations.
40. What will happen if two users have the same RSA modulus (n)?
a) Security is compromised
b) It improves encryption speed
c) It enhances security
d) Nothing changes
✅ Answer: a) Security is compromised
🔹 If two users share the same modulus (n), an attacker could derive their private keys.
41. What is the first step in RSA key generation?
a) Choosing two large prime numbers
b) Calculating the modulus (n)
c) Selecting the public exponent (e)
d) Computing the private exponent (d)
✅ Answer: a) Choosing two large prime numbers
🔹 The foundation of RSA security is based on selecting two large prime numbers, which are then multiplied to form the modulus.
42. Why are prime numbers important in RSA encryption?
a) They make key generation faster
b) Their multiplication results in unique numbers that are hard to factor
c) They are easy to encrypt and decrypt
d) They help with symmetric encryption
✅ Answer: b) Their multiplication results in unique numbers that are hard to factor
🔹 The strength of RSA relies on the difficulty of factoring the product of two large prime numbers.
43. What is a common attack against RSA if small prime numbers are used?
a) Brute-force attack
b) Dictionary attack
c) Factorization attack
d) Chosen plaintext attack
✅ Answer: c) Factorization attack
🔹 If the prime numbers used in RSA are too small, attackers can factorize the modulus and derive the private key.
44. What is the mathematical relationship between public and private keys in RSA?
a) The private key is the inverse of the public key modulo φ(n)
b) The private key is twice the public key
c) The private key is a hash of the public key
d) The public key is randomly generated and unrelated to the private key
✅ Answer: a) The private key is the inverse of the public key modulo φ(n)
🔹 The private key (d) is computed as the modular inverse of the public exponent (e) modulo φ(n), ensuring the encryption and decryption process works properly.
45. What is Euler’s Totient Function (φ) used for in RSA?
a) To determine key strength
b) To compute the private key exponent (d)
c) To encrypt messages
d) To choose the public exponent
✅ Answer: b) To compute the private key exponent (d)
🔹 Euler’s Totient Function φ(n) is used in RSA to calculate the private key exponent (d), ensuring proper modular arithmetic properties.
46. How can an attacker exploit a poorly implemented RSA encryption scheme?
a) By using a brute-force attack on the ciphertext
b) By performing a chosen-ciphertext attack
c) By modifying the key length to 128 bits
d) By swapping the private and public keys
✅ Answer: b) By performing a chosen-ciphertext attack
🔹 In a chosen-ciphertext attack, an attacker can submit specially crafted ciphertexts to learn information about the private key.
47. What is a common key size recommendation for RSA encryption today?
a) 1024 bits
b) 2048 bits
c) 4096 bits
d) 128 bits
✅ Answer: b) 2048 bits
🔹 RSA with 2048-bit keys is widely considered secure for most applications today, but 4096-bit keys may be used for added security.
48. Why is padding necessary in RSA encryption?
a) To make the ciphertext smaller
b) To prevent predictable encryption outputs
c) To reduce key size requirements
d) To make RSA symmetric
✅ Answer: b) To prevent predictable encryption outputs
🔹 Padding (e.g., OAEP) is used in RSA to add randomness and prevent attackers from recognizing patterns in encrypted messages.
49. What is the main advantage of using RSA for digital signatures?
a) It ensures confidentiality
b) It provides non-repudiation and authenticity
c) It speeds up encryption
d) It replaces symmetric encryption
✅ Answer: b) It provides non-repudiation and authenticity
🔹 RSA digital signatures allow recipients to verify the authenticity and origin of a message, preventing forgery.
50. Which of the following is NOT a valid way to generate RSA keys securely?
a) Using a hardware security module (HSM)
b) Generating keys on an air-gapped computer
c) Using a weak random number generator
d) Using OpenSSL or GPG for key generation
✅ Answer: c) Using a weak random number generator
🔹 A weak random number generator can produce predictable keys, making RSA encryption vulnerable to attacks.
51. What is the primary purpose of the RSA modulus (n)?
a) To define the encryption block size
b) To act as a unique identifier
c) To serve as a divisor in modular arithmetic
d) To determine the private key
✅ Answer: c) To serve as a divisor in modular arithmetic
🔹 The modulus (n) is a product of two large primes and is used in modular exponentiation operations for encryption and decryption.
52. What is the purpose of blinding in RSA cryptography?
a) To prevent timing attacks
b) To speed up decryption
c) To change the RSA key format
d) To allow symmetric encryption
✅ Answer: a) To prevent timing attacks
🔹 Blinding techniques introduce randomness to prevent attackers from analyzing computation times to infer private keys.
53. What property must the public exponent (e) satisfy in RSA?
a) It must be even
b) It must be prime
c) It must be co-prime with φ(n)
d) It must be a multiple of the private exponent (d)
✅ Answer: c) It must be co-prime with φ(n)
🔹 The public exponent (e) is chosen such that it has no common factors with φ(n), ensuring secure encryption.
54. How does RSA compare to Elliptic Curve Cryptography (ECC) in key size efficiency?
a) RSA requires smaller key sizes for the same security level
b) RSA requires larger key sizes for the same security level
c) RSA is faster for the same key size
d) RSA is unrelated to ECC
✅ Answer: b) RSA requires larger key sizes for the same security level
🔹 ECC provides the same level of security as RSA but with much smaller key sizes, making it more efficient.
55. What happens if the same message is encrypted with the same RSA public key multiple times?
a) The ciphertexts are identical
b) The ciphertexts are different
c) The message cannot be decrypted
d) The encryption speed increases
✅ Answer: a) The ciphertexts are identical
🔹 Without padding (e.g., OAEP), encrypting the same message with the same RSA key produces identical ciphertexts, making attacks easier.
56. Why is it not advisable to use RSA alone for encrypting large files?
a) It is computationally expensive
b) It has weak encryption
c) It does not support encryption
d) It cannot generate secure keys
✅ Answer: a) It is computationally expensive
🔹 RSA is slow for large files, so it is typically used to encrypt a symmetric key, which is then used for data encryption.
57. What cryptographic primitive does RSA rely on?
a) Diffie-Hellman key exchange
b) The difficulty of factoring large numbers
c) SHA-256 hashing
d) Secure multiparty computation
✅ Answer: b) The difficulty of factoring large numbers
🔹 RSA security depends on the difficulty of factoring large prime number products.
58. What is one advantage of RSA over symmetric encryption?
a) No need to share a secret key
b) Faster encryption speed
c) Lower CPU usage
d) Stronger hashing functions
✅ Answer: a) No need to share a secret key
🔹 Asymmetric encryption eliminates the need for secure key exchange, unlike symmetric encryption.
59. What is the purpose of the Carmichael function (λ) in RSA cryptography?
a) It speeds up encryption
b) It reduces the size of the private key
c) It is used as an alternative to Euler’s Totient Function (φ)
d) It ensures symmetric encryption compatibility
✅ Answer: c) It is used as an alternative to Euler’s Totient Function (φ)
🔹 The Carmichael function is sometimes used instead of Euler’s Totient Function (φ) to compute the RSA private exponent more efficiently.
60. Why is it important to use sufficiently large prime numbers in RSA key generation?
a) To ensure fast encryption
b) To make key exchange easier
c) To prevent factorization attacks
d) To reduce the modulus size
✅ Answer: c) To prevent factorization attacks
🔹 Using small prime numbers makes it easier for attackers to factorize the modulus and break RSA encryption.
61. What is the role of the private exponent (d) in RSA encryption?
a) It encrypts data
b) It verifies digital signatures
c) It decrypts messages
d) It generates the public key
✅ Answer: c) It decrypts messages
🔹 The private exponent (d) is used in modular exponentiation to decrypt messages encrypted with the public key.
62. What is an effective countermeasure against side-channel attacks on RSA?
a) Using larger key sizes
b) Implementing cryptographic blinding
c) Increasing encryption speed
d) Using symmetric encryption instead
✅ Answer: b) Implementing cryptographic blinding
🔹 Blinding introduces randomness into RSA computations to prevent attackers from deducing private key information through side-channel attacks.
63. Which property of RSA ensures that only the intended recipient can decrypt a message?
a) Non-repudiation
b) Asymmetry of key pairs
c) Digital signatures
d) Hashing functions
✅ Answer: b) Asymmetry of key pairs
🔹 RSA relies on asymmetric encryption, where only the private key can decrypt messages encrypted with the public key.
64. What happens if an attacker successfully factors the RSA modulus (n)?
a) They can forge digital signatures
b) They can derive the private key
c) They can prevent encryption from working
d) The RSA key pair becomes useless
✅ Answer: b) They can derive the private key
🔹 If an attacker factors n into its prime components (p and q), they can compute φ(n) and derive the private key.
65. Which of the following is NOT a common use case for RSA encryption?
a) Encrypting small amounts of data
b) Digital signatures
c) Secure key exchange
d) Full-disk encryption
✅ Answer: d) Full-disk encryption
🔹 RSA is too slow for encrypting large data volumes, so symmetric encryption is used for full-disk encryption instead.
66. How does an RSA signature work?
a) The sender encrypts the hash of a message with their private key
b) The sender encrypts the entire message with their private key
c) The sender hashes the message and stores it privately
d) The sender generates a symmetric key and signs it
✅ Answer: a) The sender encrypts the hash of a message with their private key
🔹 RSA digital signatures work by encrypting a message hash with the sender’s private key, allowing verification with the public key.
67. What does an attacker need to successfully perform a chosen-plaintext attack on RSA?
a) The private key
b) Multiple ciphertexts
c) Access to a decryption oracle
d) A brute-force algorithm
✅ Answer: c) Access to a decryption oracle
🔹 A chosen-plaintext attack requires the ability to encrypt or decrypt selected messages and analyze the outputs.
68. Why is it recommended to use padding (like OAEP) in RSA encryption?
a) To make encryption faster
b) To prevent deterministic encryption weaknesses
c) To allow longer messages to be encrypted
d) To reduce key length
✅ Answer: b) To prevent deterministic encryption weaknesses
🔹 Without padding, encrypting the same plaintext with the same RSA key always produces the same ciphertext, making attacks easier.
69. How does an RSA-based digital signature verify data authenticity?
a) By encrypting the data with the recipient’s public key
b) By decrypting the signature with the sender’s public key and comparing the hash
c) By comparing the plaintext message directly
d) By using a one-time pad for encryption
✅ Answer: b) By decrypting the signature with the sender’s public key and comparing the hash
🔹 The recipient verifies a digital signature by decrypting the hash with the sender’s public key and comparing it to the computed hash of the received message.
70. What is a common alternative to RSA for public-key encryption?
a) Advanced Encryption Standard (AES)
b) Diffie-Hellman
c) Elliptic Curve Cryptography (ECC)
d) Secure Hash Algorithm (SHA)
✅ Answer: c) Elliptic Curve Cryptography (ECC)
🔹 ECC provides similar security to RSA but with much smaller key sizes, making it more efficient.
71. Which of the following key sizes is considered insecure for RSA encryption today?
a) 1024 bits
b) 2048 bits
c) 3072 bits
d) 4096 bits
✅ Answer: a) 1024 bits
🔹 1024-bit RSA keys can be broken using modern computing power and are considered insecure.
72. What is the purpose of prime number selection in RSA key generation?
a) To speed up decryption
b) To ensure the modulus (n) is hard to factor
c) To reduce encryption time
d) To allow repeated key usage
✅ Answer: b) To ensure the modulus (n) is hard to factor
🔹 Selecting large, strong primes ensures that the modulus (n) is difficult to factorize, maintaining RSA security.
73. What is an example of a side-channel attack against RSA?
a) Brute-force attack
b) Timing attack
c) Man-in-the-middle attack
d) SQL injection
✅ Answer: b) Timing attack
🔹 Timing attacks analyze the time taken to perform cryptographic operations to infer secret keys.
74. What determines the length of an RSA ciphertext?
a) The length of the plaintext message
b) The length of the public key exponent
c) The length of the RSA modulus (n)
d) The type of encryption algorithm used
✅ Answer: c) The length of the RSA modulus (n)
🔹 The length of an RSA ciphertext is equal to the length of the modulus (n), typically 2048 or 4096 bits.
75. How does RSA ensure confidentiality?
a) By encrypting data with the recipient’s public key
b) By hashing the data before sending
c) By using symmetric key encryption
d) By digitally signing the message
✅ Answer: a) By encrypting data with the recipient’s public key
🔹 Only the recipient’s private key can decrypt the data, ensuring confidentiality.
76. Why is RSA susceptible to quantum computing attacks?
a) Quantum computers can break modular exponentiation
b) Quantum computers can factor large numbers efficiently
c) RSA uses weak encryption algorithms
d) RSA keys are easily compromised
✅ Answer: b) Quantum computers can factor large numbers efficiently
🔹 Quantum computers (via Shor’s Algorithm) can factorize RSA modulus values quickly, breaking RSA encryption.
77. What property of RSA makes it useful for digital signatures?
a) The ability to encrypt large data files
b) The asymmetric nature of the key pair
c) The fact that it is based on hashing functions
d) The use of random numbers
✅ Answer: b) The asymmetric nature of the key pair
🔹 RSA allows the use of private keys for signing and public keys for verification, making digital signatures possible.
78. What is the main difference between RSA encryption and RSA digital signatures?
a) RSA encryption uses the private key for encryption, while RSA signatures use it for signing
b) RSA encryption and digital signatures use different key sizes
c) RSA digital signatures do not use encryption
d) RSA encryption and digital signatures are the same
✅ Answer: a) RSA encryption uses the private key for encryption, while RSA signatures use it for signing
🔹 In RSA encryption, the public key encrypts data, and the private key decrypts it. In RSA digital signatures, the private key signs the data, and the public key verifies it.
79. Which of the following is a potential risk if RSA private keys are not securely stored?
a) Encrypted data can be accessed by unauthorized parties
b) The public key will be invalid
c) The RSA encryption process will fail
d) The modulus (n) will change
✅ Answer: a) Encrypted data can be accessed by unauthorized parties
🔹 If the private key is compromised, an attacker can decrypt previously encrypted data, leading to security breaches.
80. Why is RSA encryption often combined with symmetric encryption in secure communications?
a) To make encryption stronger
b) To improve efficiency since RSA is slow for large data encryption
c) To allow public key reuse
d) To avoid using a private key
✅ Answer: b) To improve efficiency since RSA is slow for large data encryption
🔹 RSA is computationally expensive, so it is typically used to encrypt a symmetric key, which then encrypts large data efficiently.
81. What is the typical key exchange process using RSA in TLS/SSL?
a) The server encrypts data with a symmetric key and shares it
b) The client encrypts a randomly generated symmetric key with the server’s public key
c) The client and server both use RSA for all encryption
d) The server provides a pre-shared key to the client
✅ Answer: b) The client encrypts a randomly generated symmetric key with the server’s public key
🔹 RSA is often used in TLS/SSL for securely exchanging a symmetric key, which is then used for encrypting data in the session.
82. What is a potential weakness of using RSA without padding schemes like OAEP?
a) It reduces encryption speed
b) It makes encryption non-deterministic
c) It makes ciphertexts predictable, allowing certain attacks
d) It increases key length requirements
✅ Answer: c) It makes ciphertexts predictable, allowing certain attacks
🔹 Without padding, encrypting the same plaintext with the same RSA key always results in the same ciphertext, making attacks easier.
83. What is a “forward secrecy” feature, and how does it relate to RSA?
a) It ensures encryption can be broken in the future
b) It prevents old messages from being decrypted if the private key is compromised
c) It speeds up RSA encryption
d) It makes RSA keys expire faster
✅ Answer: b) It prevents old messages from being decrypted if the private key is compromised
🔹 RSA alone does not provide forward secrecy; instead, protocols like TLS use ephemeral key exchanges (e.g., Diffie-Hellman) to ensure past communications remain secure.
84. How can an attacker exploit RSA if weak random number generation is used?
a) By guessing the private key directly
b) By factoring the modulus using common primes
c) By brute-forcing the ciphertext
d) By generating new RSA keys
✅ Answer: b) By factoring the modulus using common primes
🔹 If weak random number generators produce predictable primes, attackers can factor the modulus and recover the private key.
85. What is the best way to ensure RSA keys remain secure over time?
a) Use the same key indefinitely
b) Regularly rotate and generate new RSA key pairs
c) Store the private key in an unencrypted file
d) Publish the private key for transparency
✅ Answer: b) Regularly rotate and generate new RSA key pairs
🔹 Key rotation helps mitigate the risks associated with long-term RSA key exposure.
86. What is the best-known quantum algorithm that can break RSA encryption?
a) Grover’s Algorithm
b) Shor’s Algorithm
c) Blum Blum Shub Algorithm
d) RSA Factorization Algorithm
✅ Answer: b) Shor’s Algorithm
🔹 Shor’s Algorithm allows quantum computers to efficiently factor large numbers, making RSA encryption vulnerable once large-scale quantum computers become available.
87. How can organizations prepare for the potential future risk of quantum computers breaking RSA?
a) Switching to larger RSA key sizes
b) Using post-quantum cryptographic algorithms
c) Stopping the use of encryption
d) Using unencrypted channels
✅ Answer: b) Using post-quantum cryptographic algorithms
🔹 Post-quantum cryptography aims to develop encryption algorithms that remain secure even against quantum computers.
88. Why is it recommended to avoid using the same RSA key pair indefinitely?
a) It improves encryption speed
b) The key pair can become compromised over time
c) The modulus value changes automatically
d) It helps with digital signatures
✅ Answer: b) The key pair can become compromised over time
🔹 Long-lived RSA key pairs are more susceptible to compromise, so regular key rotation is recommended.
89. What is the primary reason why RSA is vulnerable to timing attacks?
a) Because it uses prime numbers
b) Because the computation time for modular exponentiation varies based on key bits
c) Because it requires public key distribution
d) Because it uses large key sizes
✅ Answer: b) Because the computation time for modular exponentiation varies based on key bits
🔹 Attackers can analyze execution times of cryptographic operations to infer private key information.
90. What is a recommended mitigation technique against RSA key leakage in cloud environments?
a) Storing private keys in plaintext for easy access
b) Using a Hardware Security Module (HSM) or cloud key management service
c) Increasing the modulus size to 8192 bits
d) Encrypting public keys before storing them
✅ Answer: b) Using a Hardware Security Module (HSM) or cloud key management service
🔹 HSMs and cloud key management services protect private keys from unauthorized access and compromise.
91. What happens if two different users generate RSA keys with the same prime numbers?
a) Their encryption will be stronger
b) They will share the same modulus, making their encryption vulnerable
c) They will be able to decrypt each other’s messages
d) Nothing, as public keys are still unique
✅ Answer: b) They will share the same modulus, making their encryption vulnerable
🔹 If two users share the same modulus (n), an attacker can compute the private keys by factoring the modulus.
92. Why are odd values usually chosen for the public exponent (e) in RSA?
a) To make encryption faster
b) To ensure compatibility with symmetric encryption
c) To make modular exponentiation easier
d) To prevent even-numbered security vulnerabilities
✅ Answer: d) To prevent even-numbered security vulnerabilities
🔹 Choosing an odd public exponent (e), such as 65537, ensures that it remains coprime with φ(n) and avoids divisibility issues.
93. What role does a Key Management System (KMS) play in RSA encryption?
a) It stores and protects RSA keys securely
b) It generates symmetric keys for encryption
c) It replaces public key cryptography
d) It encrypts messages without RSA keys
✅ Answer: a) It stores and protects RSA keys securely
🔹 A KMS securely manages and stores RSA keys to prevent unauthorized access or leakage.
94. Which of the following key storage practices is considered insecure for RSA private keys?
a) Storing them in an encrypted hardware security module (HSM)
b) Using a password-protected key store
c) Keeping them in plaintext on a public server
d) Using a cloud-based key management system
✅ Answer: c) Keeping them in plaintext on a public server
🔹 RSA private keys must never be stored in plaintext or on public servers, as this makes them vulnerable to theft and unauthorized access.
95. Which encryption scheme is considered a more efficient alternative to RSA in modern cryptography?
a) Triple DES
b) Elliptic Curve Cryptography (ECC)
c) Blowfish
d) Caesar Cipher
✅ Answer: b) Elliptic Curve Cryptography (ECC)
🔹 ECC provides the same level of security as RSA but with significantly smaller key sizes, making it more efficient.
96. What is the mathematical operation used in RSA encryption and decryption?
a) Matrix multiplication
b) Modular exponentiation
c) Symmetric key exchange
d) Exclusive OR (XOR) operation
✅ Answer: b) Modular exponentiation
🔹 RSA encryption and decryption rely on modular exponentiation, which involves raising numbers to a power modulo n.
97. What is a practical disadvantage of using large RSA key sizes (e.g., 4096 bits)?
a) It reduces encryption security
b) It significantly increases computational time
c) It makes encryption impossible
d) It prevents private key generation
✅ Answer: b) It significantly increases computational time
🔹 Larger key sizes make RSA encryption and decryption slower, impacting performance in real-world applications.
98. Why is 65537 a commonly chosen value for the RSA public exponent (e)?
a) It is the smallest prime number
b) It reduces brute-force attacks
c) It allows faster modular exponentiation while maintaining security
d) It is required by the RSA standard
✅ Answer: c) It allows faster modular exponentiation while maintaining security
🔹 65537 is a prime number that balances computational efficiency with strong security.
99. How does an attacker attempt to break RSA encryption using a lattice attack?
a) By analyzing side-channel information
b) By using quantum algorithms
c) By finding small values in the RSA key structure
d) By attempting brute-force decryption
✅ Answer: c) By finding small values in the RSA key structure
🔹 Lattice-based attacks exploit weaknesses in RSA implementations that use small private exponents or poorly chosen keys.
100. What is a key difference between RSA and AES encryption?
a) RSA is a symmetric encryption algorithm, while AES is asymmetric
b) AES is faster for encrypting large data, while RSA is slower
c) RSA is primarily used for bulk encryption, while AES is for key exchange
d) RSA encryption uses block ciphers, while AES does not
✅ Answer: b) AES is faster for encrypting large data, while RSA is slower
🔹 AES is a symmetric algorithm optimized for fast encryption of large amounts of data, whereas RSA is better suited for key exchange and digital signatures.
101. Why does RSA require prime numbers that are randomly generated?
a) To ensure encryption speed
b) To make factorization difficult
c) To simplify modular arithmetic
d) To allow backward compatibility with older cryptographic systems
✅ Answer: b) To make factorization difficult
🔹 Randomly selecting large prime numbers makes it computationally difficult for attackers to factorize the modulus (n).
102. What is an optimal way to generate strong RSA key pairs?
a) Using a secure cryptographic random number generator
b) Choosing two small prime numbers manually
c) Using a precomputed list of primes
d) Selecting arbitrary numbers for p and q
✅ Answer: a) Using a secure cryptographic random number generator
🔹 Secure random number generators ensure that RSA keys are unpredictable and resistant to attacks.
103. Which attack can be mitigated by using a random padding scheme like OAEP in RSA encryption?
a) Brute-force attacks
b) Chosen-plaintext attacks
c) Side-channel attacks
d) Man-in-the-middle attacks
✅ Answer: b) Chosen-plaintext attacks
🔹 OAEP padding prevents attackers from exploiting predictable encryption patterns in chosen-plaintext attacks.
104. What is a possible reason why an RSA key might need to be revoked?
a) The modulus (n) became too large
b) The private key has been exposed or compromised
c) The public exponent (e) is greater than 65537
d) The encrypted messages are too short
✅ Answer: b) The private key has been exposed or compromised
🔹 If an RSA private key is leaked, it must be revoked to prevent unauthorized decryption and impersonation.
105. Why is RSA not used in blockchain transactions like Bitcoin?
a) RSA is too slow and inefficient for blockchain applications
b) RSA keys cannot be generated on a blockchain
c) RSA does not support encryption
d) RSA does not allow for digital signatures
✅ Answer: a) RSA is too slow and inefficient for blockchain applications
🔹 Bitcoin and other blockchain networks use elliptic curve cryptography (ECC) because it is more efficient than RSA.
106. What is the primary advantage of RSA-based digital signatures?
a) They provide integrity and authenticity for messages
b) They encrypt data at high speeds
c) They work only with symmetric keys
d) They cannot be verified by a third party
✅ Answer: a) They provide integrity and authenticity for messages
🔹 RSA digital signatures ensure that a message is authentic and has not been tampered with.
107. What is a Certificate Authority (CA) responsible for in RSA-based cryptographic systems?
a) Storing public keys
b) Verifying and signing digital certificates
c) Generating private keys for users
d) Encrypting RSA messages
✅ Answer: b) Verifying and signing digital certificates
🔹 Certificate Authorities verify the authenticity of RSA public keys and issue digital certificates.
108. What type of RSA attack takes advantage of poorly chosen private exponents?
a) Timing attacks
b) Wiener’s attack
c) Chosen-ciphertext attacks
d) Brute-force attacks
✅ Answer: b) Wiener’s attack
🔹 Wiener’s attack exploits weak private exponents (d) when they are too small relative to the modulus.
109. What is the primary mathematical reason that RSA encryption is secure?
a) The difficulty of solving linear equations
b) The difficulty of factoring large composite numbers
c) The inability to calculate modular exponentiation
d) The unpredictable nature of hashing algorithms
✅ Answer: b) The difficulty of factoring large composite numbers
🔹 RSA security is based on the fact that factoring a large composite number (modulus n) into its prime factors is computationally hard.
110. What is one disadvantage of using a very large RSA key (e.g., 8192 bits)?
a) The encryption becomes weaker
b) It is computationally expensive and slow
c) The public key becomes invalid
d) The private key cannot be stored
✅ Answer: b) It is computationally expensive and slow
🔹 Larger RSA key sizes increase security but significantly slow down encryption and decryption operations.
111. Which cryptographic protocol often uses RSA for secure key exchange?
a) TLS/SSL
b) SHA-256
c) AES-256
d) WPA2
✅ Answer: a) TLS/SSL
🔹 RSA is widely used in TLS/SSL protocols to establish secure communication between web browsers and servers.
112. What type of padding does RSA typically use to improve security?
a) AES-GCM
b) Optimal Asymmetric Encryption Padding (OAEP)
c) Block padding
d) HMAC padding
✅ Answer: b) Optimal Asymmetric Encryption Padding (OAEP)
🔹 OAEP prevents certain attacks by adding randomness to RSA encryption, ensuring that the same message does not produce the same ciphertext.
113. How does RSA provide authentication in digital communication?
a) By encrypting messages with the sender’s private key
b) By hashing all messages before sending
c) By verifying encryption with the recipient’s private key
d) By only allowing symmetric encryption
✅ Answer: a) By encrypting messages with the sender’s private key
🔹 Digital signatures use the sender’s private key to sign messages, allowing recipients to verify authenticity using the public key.
114. Why are large prime numbers used in RSA encryption instead of small primes?
a) Large primes improve encryption speed
b) Large primes make factorization more difficult
c) Small primes require more storage
d) Small primes are incompatible with modular exponentiation
✅ Answer: b) Large primes make factorization more difficult
🔹 The security of RSA relies on the difficulty of factoring a large modulus, which is the product of two large prime numbers.
115. What is the main reason why RSA alone is not used for encrypting large files?
a) RSA keys cannot be used multiple times
b) RSA has a limited block size
c) RSA encryption is too slow for large amounts of data
d) RSA is incompatible with modern systems
✅ Answer: c) RSA encryption is too slow for large amounts of data
🔹 RSA is computationally expensive, so it is usually used to encrypt a symmetric key, which then encrypts large files efficiently.
116. What is the relationship between the RSA modulus (n) and the prime numbers p and q?
a) n is the sum of p and q
b) n is the product of p and q
c) n is the greatest common divisor (GCD) of p and q
d) n is unrelated to p and q
✅ Answer: b) n is the product of p and q
🔹 The modulus (n) in RSA is calculated as n = p × q, where p and q are two large prime numbers.
117. What is an advantage of using RSA over password-based authentication?
a) RSA is easier to remember than passwords
b) RSA does not require storing secret keys on a server
c) RSA prevents all types of cyberattacks
d) RSA is faster than passwords
✅ Answer: b) RSA does not require storing secret keys on a server
🔹 RSA eliminates the need for password storage by using public-key cryptography for authentication.
118. How does RSA ensure that an encrypted message can only be decrypted by the intended recipient?
a) The sender uses a randomly generated key for each message
b) The message is encrypted using the recipient’s public key
c) The message is always signed with a private key
d) RSA does not provide encryption, only authentication
✅ Answer: b) The message is encrypted using the recipient’s public key
🔹 Since only the recipient has the corresponding private key, they are the only one who can decrypt the message.
119. What is a common way to securely distribute RSA public keys?
a) Storing them in a shared plaintext file
b) Sending them via an unencrypted email
c) Using a Certificate Authority (CA) to sign and verify them
d) Encrypting them with AES
✅ Answer: c) Using a Certificate Authority (CA) to sign and verify them
🔹 Certificate Authorities (CAs) ensure that RSA public keys are valid and belong to the intended entity.
120. How can an organization ensure that expired RSA keys are not reused?
a) By encrypting the private key with the public key
b) By using a key revocation mechanism in a Public Key Infrastructure (PKI)
c) By making RSA keys public
d) By using a symmetric key for encryption instead
✅ Answer: b) By using a key revocation mechanism in a Public Key Infrastructure (PKI)
🔹 PKI systems allow organizations to revoke and manage RSA keys to prevent their reuse after expiration.
121. What is the main purpose of the public key in RSA encryption?
a) To decrypt messages
b) To encrypt messages or verify signatures
c) To store private keys securely
d) To generate new encryption keys
✅ Answer: b) To encrypt messages or verify signatures
🔹 In RSA, the public key is used to encrypt messages (for confidentiality) or verify digital signatures.
122. Which cryptographic algorithm does RSA typically work alongside for secure web communication?
a) AES
b) MD5
c) SHA-1
d) DES
✅ Answer: a) AES
🔹 RSA is often used to securely exchange an AES key, which is then used for encrypting web traffic due to its efficiency.
123. What is the recommended minimum key size for RSA to be secure against brute-force attacks as of 2025?
a) 1024 bits
b) 2048 bits
c) 4096 bits
d) 8192 bits
✅ Answer: b) 2048 bits
🔹 2048-bit RSA keys are currently considered secure, while 4096-bit keys provide even stronger security for long-term protection.
124. Why is modular arithmetic used in RSA encryption?
a) It ensures that encrypted data is always unique
b) It allows mathematical operations to wrap around within a fixed range
c) It speeds up encryption
d) It ensures perfect randomness in keys
✅ Answer: b) It allows mathematical operations to wrap around within a fixed range
🔹 RSA relies on modular exponentiation, which is performed within a defined modulus (n) to keep calculations within a specific range.
125. What is a potential risk of using small values for the RSA public exponent (e)?
a) It makes encryption slower
b) It weakens security against certain attacks
c) It increases key size
d) It prevents factorization
✅ Answer: b) It weakens security against certain attacks
🔹 Using small values like 3 for the public exponent can make RSA susceptible to attacks such as low-exponent attacks.
126. What is a practical advantage of using RSA for key exchange rather than direct data encryption?
a) It reduces encryption time for large data
b) It improves compression rates
c) It does not require public key infrastructure
d) It prevents MITM attacks
✅ Answer: a) It reduces encryption time for large data
🔹 RSA is slow for bulk data encryption, so it is often used to encrypt a symmetric key, which is then used for fast encryption of large files.
127. What kind of attack can exploit weak padding in RSA encryption?
a) RSA Bleichenbacher attack
b) Brute-force attack
c) Man-in-the-middle attack
d) Buffer overflow attack
✅ Answer: a) RSA Bleichenbacher attack
🔹 The Bleichenbacher attack targets weak PKCS#1 v1.5 padding, allowing attackers to decrypt messages without access to the private key.
128. What is a primary factor that influences the security strength of an RSA key pair?
a) The total number of keys generated
b) The randomness of the prime numbers used
c) The length of the public exponent (e)
d) The number of messages encrypted
✅ Answer: b) The randomness of the prime numbers used
🔹 RSA security depends on using unpredictable and large prime numbers to generate secure key pairs.
129. What is the best way to securely store an RSA private key?
a) In an encrypted hardware security module (HSM)
b) In a plaintext file on the desktop
c) In an unencrypted USB drive
d) In a text document on a cloud storage service
✅ Answer: a) In an encrypted hardware security module (HSM)
🔹 An HSM provides a secure environment for storing and managing private keys, preventing unauthorized access.
130. Which of the following is NOT a valid use case for RSA?
a) Encrypting small messages
b) Digital signatures
c) Full-disk encryption
d) Secure key exchange
✅ Answer: c) Full-disk encryption
🔹 RSA is too slow for encrypting large amounts of data, so symmetric encryption (e.g., AES) is used for full-disk encryption instead.
131. What is one way RSA encryption is made more efficient in digital communication?
a) By using quantum computers
b) By combining it with symmetric encryption
c) By using a single key for encryption and decryption
d) By removing the modulus from calculations
✅ Answer: b) By combining it with symmetric encryption
🔹 RSA is often used to encrypt a symmetric key, which is then used for fast and efficient encryption of data.
132. What happens if the same message is encrypted multiple times with the same RSA key?
a) The ciphertexts are identical without padding
b) The ciphertexts are always different
c) The private key is leaked
d) The encryption process stops working
✅ Answer: a) The ciphertexts are identical without padding
🔹 Without padding, encrypting the same message multiple times with the same RSA key produces identical ciphertexts, which makes attacks easier.
133. How does RSA encryption help in securing online banking transactions?
a) By encrypting all data stored on the bank’s servers
b) By securing key exchange in SSL/TLS connections
c) By replacing all symmetric encryption algorithms
d) By reducing the need for authentication
✅ Answer: b) By securing key exchange in SSL/TLS connections
🔹 RSA is commonly used to exchange symmetric encryption keys securely in online banking systems.
134. What is the effect of choosing very large prime numbers in RSA key generation?
a) It increases encryption speed
b) It strengthens security but makes computations slower
c) It decreases key size
d) It makes public keys unnecessary
✅ Answer: b) It strengthens security but makes computations slower
🔹 Larger prime numbers make RSA keys harder to break but increase computational complexity.
135. What is one reason why RSA encryption may fail in practical implementations?
a) The lack of randomness in prime number selection
b) The use of elliptic curve cryptography
c) The presence of symmetric encryption
d) The high speed of encryption
✅ Answer: a) The lack of randomness in prime number selection
🔹 If predictable prime numbers are used, an attacker can factorize the modulus and recover the private key.
136. How does RSA protect against replay attacks in secure communications?
a) By using nonces or timestamps
b) By increasing the public key size
c) By using a fixed ciphertext
d) By removing the public exponent (e)
✅ Answer: a) By using nonces or timestamps
🔹 Replay attacks are prevented by including unique identifiers, such as nonces or timestamps, in encrypted messages.
137. What is a common attack on RSA implementations that fail to use proper padding?
a) Chosen-ciphertext attack
b) SQL injection attack
c) Phishing attack
d) Rainbow table attack
✅ Answer: a) Chosen-ciphertext attack
🔹 Without proper padding, RSA encryption can be vulnerable to chosen-ciphertext attacks like Bleichenbacher’s attack.
138. What is the primary function of a digital certificate in RSA-based encryption?
a) To encrypt messages directly
b) To verify the authenticity of public keys
c) To store private keys securely
d) To replace encryption algorithms
✅ Answer: b) To verify the authenticity of public keys
🔹 Digital certificates, issued by Certificate Authorities (CAs), help verify that a public key belongs to a trusted entity.
139. What makes RSA encryption impractical for encrypting large amounts of data directly?
a) RSA keys cannot store large data
b) RSA encryption is computationally expensive and slow
c) RSA does not support encryption, only key exchange
d) RSA requires a trusted third party
✅ Answer: b) RSA encryption is computationally expensive and slow
🔹 RSA is best used for encrypting small amounts of data like keys, while symmetric encryption (e.g., AES) is used for bulk data encryption.
140. Which type of cryptographic attack attempts to factorize the RSA modulus (n) into its prime components?
a) Timing attack
b) Factorization attack
c) Chosen-plaintext attack
d) Side-channel attack
✅ Answer: b) Factorization attack
🔹 A factorization attack tries to break RSA by computing the two prime factors (p and q) of the modulus (n).
141. What is the primary reason why RSA cannot provide perfect forward secrecy (PFS) on its own?
a) RSA keys are stored permanently
b) RSA encryption relies on shared secrets
c) If the RSA private key is compromised, all past encrypted messages can be decrypted
d) RSA cannot encrypt data
✅ Answer: c) If the RSA private key is compromised, all past encrypted messages can be decrypted
🔹 RSA does not provide perfect forward secrecy because if an attacker obtains the private key, they can decrypt all past communications.
142. What is the role of a digital signature in an RSA-based authentication system?
a) It ensures the integrity and authenticity of a message
b) It encrypts a message for confidentiality
c) It prevents the need for key exchange
d) It replaces the public key in encryption
✅ Answer: a) It ensures the integrity and authenticity of a message
🔹 RSA digital signatures confirm that a message was sent by a specific sender and has not been altered.
143. What is the impact of a compromised RSA private key?
a) The public key becomes unusable
b) The RSA modulus must be changed
c) Encrypted messages and digital signatures can be decrypted and forged
d) The encryption algorithm must be replaced
✅ Answer: c) Encrypted messages and digital signatures can be decrypted and forged
🔹 A compromised private key allows an attacker to decrypt previously encrypted messages and create fake digital signatures.
144. What is a common reason for revoking an RSA key pair?
a) The key pair was used too many times
b) The private key has been leaked or compromised
c) The public key is too long
d) The modulus (n) is smaller than 1024 bits
✅ Answer: b) The private key has been leaked or compromised
🔹 If a private key is leaked, it must be revoked to prevent unauthorized decryption and impersonation.
145. What happens if an RSA key pair is generated using non-random primes?
a) The encryption process fails
b) The key pair remains secure
c) The key pair becomes predictable and easier to break
d) The modulus (n) is always even
✅ Answer: c) The key pair becomes predictable and easier to break
🔹 If the prime numbers used in key generation are not random, attackers can use precomputed tables or patterns to factorize the modulus and retrieve the private key.
146. Which protocol is commonly used for securing email communication with RSA encryption?
a) SSL/TLS
b) PGP/GPG
c) WPA2
d) SHA-256
✅ Answer: b) PGP/GPG
🔹 Pretty Good Privacy (PGP) and GNU Privacy Guard (GPG) use RSA encryption for securing email communication.
147. What happens if an attacker can successfully perform a chosen-ciphertext attack on an RSA-encrypted message?
a) The attacker can determine the plaintext message
b) The attacker gains access to the private key
c) The attacker can factorize the modulus (n)
d) The RSA key pair becomes invalid
✅ Answer: a) The attacker can determine the plaintext message
🔹 Chosen-ciphertext attacks, such as Bleichenbacher’s attack, can allow attackers to deduce plaintext information without needing the private key.
148. What is the benefit of using a cryptographic hash function with RSA digital signatures?
a) It compresses the message before encryption
b) It speeds up signature verification
c) It ensures message integrity and prevents tampering
d) It replaces the need for a private key
✅ Answer: c) It ensures message integrity and prevents tampering
🔹 Cryptographic hash functions (e.g., SHA-256) are used in RSA signatures to verify that a message has not been altered.
149. What is the purpose of a Key Escrow system in RSA encryption?
a) To securely store and retrieve private keys when needed
b) To make encryption faster
c) To prevent key revocation
d) To generate public keys for multiple users
✅ Answer: a) To securely store and retrieve private keys when needed
🔹 Key Escrow systems are used in enterprise environments where a trusted authority stores copies of private keys for recovery purposes.
150. What mathematical operation is required to verify an RSA digital signature?
a) Modular exponentiation using the public key
b) Prime factorization of the modulus
c) Exclusive OR (XOR) operation
d) Hashing with MD5
✅ Answer: a) Modular exponentiation using the public key
🔹 RSA digital signatures are verified by raising the signature to the power of the public exponent (e) modulo n.
151. How does the use of random padding in RSA encryption improve security?
a) It increases encryption speed
b) It prevents the creation of identical ciphertexts for the same plaintext
c) It reduces key size requirements
d) It allows the same key pair to be used for multiple encryptions
✅ Answer: b) It prevents the creation of identical ciphertexts for the same plaintext
🔹 Without padding, RSA encryption is deterministic, meaning the same plaintext always produces the same ciphertext, making it vulnerable to certain attacks.
152. Which cryptographic attack can exploit the use of small RSA private exponents?
a) Wiener’s attack
b) Birthday attack
c) Padding oracle attack
d) SQL injection
✅ Answer: a) Wiener’s attack
🔹 Wiener’s attack exploits weak RSA private exponents (d) that are too small relative to the modulus (n), making them susceptible to efficient cryptanalysis.
153. What is the best way to prevent an attacker from brute-forcing an RSA private key?
a) Using a sufficiently large key size
b) Encrypting the private key with the public key
c) Avoiding the use of digital signatures
d) Storing the private key in plaintext
✅ Answer: a) Using a sufficiently large key size
🔹 Larger key sizes (2048+ bits) make brute-force attacks computationally infeasible.
154. Which security property does RSA NOT provide on its own?
a) Confidentiality
b) Integrity
c) Availability
d) Authentication
✅ Answer: c) Availability
🔹 RSA provides confidentiality, integrity, and authentication but does not ensure availability (protection against denial-of-service attacks).
155. What cryptographic technique is commonly used to generate RSA key pairs?
a) Prime number generation and modular arithmetic
b) Hashing algorithms
c) Symmetric key exchange
d) Randomized block ciphers
✅ Answer: a) Prime number generation and modular arithmetic
🔹 RSA key generation involves selecting two large prime numbers and using modular arithmetic to compute the key components.
156. What makes RSA decryption slower than encryption?
a) The encryption process requires more computation
b) The private exponent (d) is usually larger than the public exponent (e)
c) The encryption process uses complex mathematical operations
d) The decryption process requires prime number generation
✅ Answer: b) The private exponent (d) is usually larger than the public exponent (e)
🔹 RSA decryption is slower because the private exponent (d) is often much larger than the public exponent (e), making modular exponentiation more computationally expensive.
157. Why is it important to keep the private key confidential in RSA encryption?
a) To ensure the public key remains valid
b) To prevent unauthorized decryption of messages
c) To increase encryption speed
d) To allow message authentication
✅ Answer: b) To prevent unauthorized decryption of messages
🔹 If the private key is leaked, an attacker can decrypt confidential messages and potentially forge digital signatures.
158. What is the main reason why an attacker cannot derive the private key from the public key in RSA?
a) The modulus (n) is too small
b) The public exponent (e) is always random
c) Factoring large prime numbers is computationally difficult
d) The private key is never used in encryption
✅ Answer: c) Factoring large prime numbers is computationally difficult
🔹 RSA security relies on the fact that factoring a large number into its two prime factors is extremely difficult.
159. How does RSA prevent message tampering?
a) By encrypting the message twice
b) By using digital signatures
c) By requiring symmetric encryption
d) By using public key exchange
✅ Answer: b) By using digital signatures
🔹 RSA digital signatures allow recipients to verify that a message was not altered during transmission.
160. What is a common way attackers attempt to compromise RSA encryption?
a) Brute-force guessing the public key
b) Attempting to factor the modulus (n)
c) Randomly generating private keys
d) Modifying the RSA algorithm
✅ Answer: b) Attempting to factor the modulus (n)
🔹 RSA security is based on the difficulty of factoring large prime numbers. If an attacker successfully factors n, they can derive the private key.
161. Which component of RSA key generation ensures that decryption is only possible with the correct private key?
a) The public exponent (e)
b) The modulus (n)
c) Euler’s Totient Function (φ)
d) The prime factors (p and q)
✅ Answer: c) Euler’s Totient Function (φ)
🔹 Euler’s Totient Function (φ) is used to compute the private exponent (d), ensuring only the correct private key can decrypt messages.
162. Why is it recommended to periodically update RSA key pairs?
a) To improve encryption speed
b) To prevent quantum computing attacks
c) To mitigate the risk of key compromise over time
d) To avoid generating new prime numbers
✅ Answer: c) To mitigate the risk of key compromise over time
🔹 Regularly updating RSA keys reduces the chances of compromise and ensures continued security.
163. How does RSA differ from symmetric encryption algorithms like AES?
a) RSA uses the same key for encryption and decryption
b) RSA uses asymmetric key pairs instead of a shared secret key
c) RSA encrypts data in blocks
d) RSA is always faster than AES
✅ Answer: b) RSA uses asymmetric key pairs instead of a shared secret key
🔹 RSA uses a public and private key pair, whereas symmetric encryption (like AES) uses a single shared key for both encryption and decryption.
164. What happens if an RSA key is too short?
a) It becomes computationally infeasible to decrypt messages
b) It is more vulnerable to factorization attacks
c) It increases encryption speed without security risks
d) It makes key generation impossible
✅ Answer: b) It is more vulnerable to factorization attacks
🔹 Short RSA keys are easier to factor, making them insecure against modern computing power.
165. What is the recommended padding scheme to protect RSA encryption from attacks?
a) PKCS#1 v1.5
b) Optimal Asymmetric Encryption Padding (OAEP)
c) ECB mode padding
d) XOR-based padding
✅ Answer: b) Optimal Asymmetric Encryption Padding (OAEP)
🔹 OAEP padding adds randomness and prevents predictable ciphertext patterns, making RSA encryption more secure.
166. Why is it important to verify an RSA public key before using it for encryption?
a) To ensure encryption speed
b) To prevent man-in-the-middle attacks
c) To avoid excessive key lengths
d) To randomly generate new primes
✅ Answer: b) To prevent man-in-the-middle attacks
🔹 If an attacker replaces a legitimate public key with their own, they can intercept encrypted messages.
167. What is one way an attacker could speed up the factorization of an RSA modulus?
a) By using quantum computing techniques
b) By brute-force searching for prime numbers
c) By using XOR operations
d) By increasing key size
✅ Answer: a) By using quantum computing techniques
🔹 Quantum computers could use Shor’s algorithm to efficiently factor RSA moduli, making RSA encryption vulnerable in the future.
168. What is the main reason RSA encryption is computationally intensive?
a) The use of random prime numbers
b) The complexity of modular exponentiation
c) The use of hashing functions
d) The size of digital signatures
✅ Answer: b) The complexity of modular exponentiation
🔹 RSA encryption and decryption require modular exponentiation, which is computationally expensive for large key sizes.
169. What makes RSA more suitable for digital signatures than symmetric encryption?
a) RSA is faster than symmetric encryption
b) RSA signatures can be verified without sharing a secret key
c) RSA keys are smaller than symmetric keys
d) RSA does not require a trusted third party
✅ Answer: b) RSA signatures can be verified without sharing a secret key
🔹 RSA digital signatures use a public key for verification, making them ideal for authentication without requiring a shared secret.
170. Why is RSA key length increasing over time?
a) To support longer messages
b) To counter advances in computing power
c) To reduce encryption time
d) To improve compatibility with older systems
✅ Answer: b) To counter advances in computing power
🔹 As computers become more powerful, RSA keys need to be longer to remain secure against factorization attacks.
171. What role does a Trusted Platform Module (TPM) play in RSA security?
a) It generates and securely stores RSA keys
b) It replaces RSA encryption with symmetric encryption
c) It speeds up RSA encryption
d) It acts as a certificate authority
✅ Answer: a) It generates and securely stores RSA keys
🔹 A TPM is a hardware-based security module that protects RSA keys from theft or unauthorized access.
172. What is the relationship between the RSA modulus (n) and key strength?
a) A larger modulus provides greater security
b) A smaller modulus increases encryption speed and security
c) The modulus size does not impact security
d) The modulus size affects only encryption speed
✅ Answer: a) A larger modulus provides greater security
🔹 A larger modulus makes factorization attacks more difficult, increasing the security of RSA encryption.
173. What is the main purpose of the RSA key pair in public key infrastructure (PKI)?
a) To store encryption keys for symmetric encryption
b) To enable secure key exchange and authentication
c) To replace the need for digital certificates
d) To generate random numbers for hashing
✅ Answer: b) To enable secure key exchange and authentication
🔹 RSA key pairs are a fundamental part of PKI, ensuring secure communication and authentication.
174. Which part of an RSA key pair must be kept secret to maintain security?
a) Public exponent (e)
b) Private exponent (d)
c) Modulus (n)
d) Public key
✅ Answer: b) Private exponent (d)
🔹 The private exponent (d) must be kept secret because it is used to decrypt messages and sign data securely.
175. What cryptographic operation does RSA use for digital signatures?
a) Encrypting the message with the sender’s public key
b) Hashing the message and encrypting the hash with the sender’s private key
c) Encrypting the message with a symmetric key
d) Using XOR operations for message authentication
✅ Answer: b) Hashing the message and encrypting the hash with the sender’s private key
🔹 RSA digital signatures are created by encrypting a hash of the message with the sender’s private key.
176. What would happen if an RSA public key were kept secret instead of being shared?
a) Encryption and verification would still work normally
b) No one would be able to encrypt messages or verify signatures
c) The public key would still function as a private key
d) The RSA encryption algorithm would fail
✅ Answer: b) No one would be able to encrypt messages or verify signatures
🔹 The public key must be shared so that others can encrypt messages or verify signatures from the owner of the private key.
177. Why is RSA encryption often used in combination with symmetric encryption?
a) To provide better authentication
b) To speed up encryption and decryption processes
c) To avoid the need for key exchange
d) To remove the need for public keys
✅ Answer: b) To speed up encryption and decryption processes
🔹 RSA is computationally expensive, so it is typically used to encrypt a symmetric key, which is then used for bulk encryption.
178. What is the main advantage of using a hardware security module (HSM) for RSA key storage?
a) It allows easy key sharing
b) It protects private keys from unauthorized access
c) It speeds up encryption
d) It makes key revocation unnecessary
✅ Answer: b) It protects private keys from unauthorized access
🔹 HSMs provide secure storage for RSA keys, preventing them from being stolen or compromised.
179. What is a primary reason why RSA encryption is vulnerable to quantum computing?
a) Quantum computers can break symmetric encryption
b) Quantum algorithms can efficiently factor large numbers
c) RSA relies on insecure key exchange methods
d) Quantum computing reduces key sizes
✅ Answer: b) Quantum algorithms can efficiently factor large numbers
🔹 Shor’s algorithm enables quantum computers to factor large numbers, breaking RSA encryption.
180. How does an attacker perform a timing attack against RSA encryption?
a) By analyzing the time it takes for decryption operations
b) By modifying the public key
c) By intercepting RSA-encrypted messages
d) By changing the padding scheme
✅ Answer: a) By analyzing the time it takes for decryption operations
🔹 Timing attacks exploit variations in computation time to infer private key information.
181. What should organizations do to prepare for the threat of quantum computing to RSA encryption?
a) Use smaller RSA key sizes
b) Switch to post-quantum cryptographic algorithms
c) Encrypt public keys to improve security
d) Stop using encryption altogether
✅ Answer: b) Switch to post-quantum cryptographic algorithms
🔹 Post-quantum cryptographic methods are being developed to counteract quantum computing threats.
182. What is one of the primary goals of an RSA key revocation process?
a) To generate a new public key automatically
b) To prevent a compromised private key from being used
c) To allow decryption of past messages
d) To remove digital signatures from files
✅ Answer: b) To prevent a compromised private key from being used
🔹 Key revocation ensures that if a private key is compromised, it can no longer be used for decryption or signing.
183. What is a common way to distribute RSA public keys securely?
a) Through a Certificate Authority (CA)
b) By emailing them in plaintext
c) By storing them in a public GitHub repository
d) By encrypting them with the private key
✅ Answer: a) Through a Certificate Authority (CA)
🔹 Certificate Authorities (CAs) verify and distribute RSA public keys securely.
184. Which cryptographic weakness can arise from using predictable RSA prime numbers?
a) The public exponent (e) becomes invalid
b) The modulus (n) can be easily factorized
c) Digital signatures stop working
d) The encryption algorithm needs modification
✅ Answer: b) The modulus (n) can be easily factorized
🔹 If RSA prime numbers are predictable, attackers can factorize the modulus (n) and recover the private key.
185. What makes RSA an asymmetric encryption algorithm?
a) It uses the same key for encryption and decryption
b) It relies on symmetric key exchange
c) It uses a public and private key pair
d) It encrypts data in blocks
✅ Answer: c) It uses a public and private key pair
🔹 Asymmetric encryption means that different keys are used for encryption (public key) and decryption (private key).
186. What is the relationship between an RSA key’s security and its bit length?
a) Longer keys are harder to factor and provide stronger security
b) Shorter keys provide better security
c) RSA security is independent of key length
d) Key length affects encryption speed but not security
✅ Answer: a) Longer keys are harder to factor and provide stronger security
🔹 Larger RSA keys (e.g., 2048 bits) are more secure because they are harder to factorize.
187. What happens if two different users generate RSA keys using the same prime numbers?
a) Their encryption becomes stronger
b) They can decrypt each other’s messages
c) Their public keys will be incompatible
d) The RSA algorithm will detect the issue and reject the keys
✅ Answer: b) They can decrypt each other’s messages
🔹 If two users have the same modulus (n), they share the same private key, compromising security.
188. How can RSA encryption protect data in transit?
a) By creating digital signatures
b) By encrypting data with the recipient’s public key
c) By storing encryption keys in the cloud
d) By ensuring passwords are strong
✅ Answer: b) By encrypting data with the recipient’s public key
🔹 Only the recipient with the matching private key can decrypt the data, ensuring confidentiality.
189. Why do modern systems increasingly use elliptic curve cryptography (ECC) instead of RSA?
a) ECC requires larger key sizes than RSA
b) ECC provides similar security with smaller key sizes
c) ECC is based on hashing rather than encryption
d) ECC does not require a private key
✅ Answer: b) ECC provides similar security with smaller key sizes
🔹 ECC is more efficient than RSA because it provides the same level of security with much smaller key sizes.
190. What is the biggest risk if RSA encryption is implemented without proper padding?
a) The encryption process will fail
b) Messages will be easy to decrypt using chosen-ciphertext attacks
c) The private key will stop working
d) The modulus (n) will become too large
✅ Answer: b) Messages will be easy to decrypt using chosen-ciphertext attacks
🔹 Without padding (e.g., OAEP), attackers can exploit vulnerabilities such as Bleichenbacher’s attack to decrypt RSA messages.
191. What is the purpose of the Chinese Remainder Theorem (CRT) in RSA decryption?
a) To increase the security of RSA encryption
b) To speed up RSA decryption by performing computations separately for p and q
c) To generate prime numbers for key creation
d) To prevent chosen-ciphertext attacks
✅ Answer: b) To speed up RSA decryption by performing computations separately for p and q
🔹 CRT optimizes RSA decryption by computing modular exponentiations separately for p and q, reducing computation time.
192. What is the role of RSA in securing HTTPS connections?
a) Encrypting entire web pages
b) Authenticating digital certificates and performing key exchange
c) Replacing TLS encryption protocols
d) Compressing encrypted messages for efficiency
✅ Answer: b) Authenticating digital certificates and performing key exchange
🔹 RSA is used in HTTPS to verify certificates and establish a secure connection by encrypting symmetric keys for secure communication.
193. What type of RSA attack can exploit poorly chosen private exponents?
a) RSA Blinding Attack
b) Wiener’s Attack
c) Brute-force Attack
d) Man-in-the-middle Attack
✅ Answer: b) Wiener’s Attack
🔹 Wiener’s attack exploits weak RSA private exponents (d) that are too small, making them susceptible to cryptanalysis.
194. Why is it important to use padding (e.g., OAEP) in RSA encryption?
a) To reduce the size of the encrypted message
b) To prevent predictable ciphertexts and mitigate attacks
c) To make encryption faster
d) To allow the same key pair to be used for multiple encryptions
✅ Answer: b) To prevent predictable ciphertexts and mitigate attacks
🔹 Padding schemes like OAEP add randomness, preventing attackers from predicting ciphertext patterns and exploiting vulnerabilities.
195. What happens if an attacker successfully factors the modulus (n) in RSA?
a) They can recover the private key and decrypt messages
b) The encryption process becomes faster
c) The public key becomes invalid
d) The private key must be regenerated but remains secure
✅ Answer: a) They can recover the private key and decrypt messages
🔹 Factoring the modulus (n) reveals the private key, allowing attackers to decrypt encrypted messages.
196. Why is the public exponent (e) in RSA often chosen as 65537?
a) It is the largest possible prime number
b) It provides a good balance between security and computational efficiency
c) It is required for compatibility with modern web browsers
d) It is a random number generated for each encryption
✅ Answer: b) It provides a good balance between security and computational efficiency
🔹 65537 is commonly used because it is a prime number that enables efficient encryption without compromising security.
197. What is one major downside of using RSA for key exchange in TLS compared to Diffie-Hellman?
a) RSA does not support key exchange
b) RSA does not provide perfect forward secrecy (PFS)
c) RSA key exchange is faster than Diffie-Hellman
d) RSA keys cannot be used for authentication
✅ Answer: b) RSA does not provide perfect forward secrecy (PFS)
🔹 Unlike ephemeral Diffie-Hellman, RSA key exchange does not provide forward secrecy, meaning past communications can be decrypted if the private key is compromised.
198. What happens when RSA is used without a secure key management strategy?
a) Private keys may be exposed, compromising security
b) Encryption becomes more efficient
c) Messages become impossible to decrypt
d) Public keys become insecure
✅ Answer: a) Private keys may be exposed, compromising security
🔹 Secure key management is essential to prevent unauthorized access to private keys, ensuring the integrity of RSA encryption.
199. What is the function of an RSA digital signature?
a) To encrypt messages for confidentiality
b) To verify the authenticity and integrity of a message
c) To generate encryption keys
d) To speed up the encryption process
✅ Answer: b) To verify the authenticity and integrity of a message
🔹 RSA digital signatures confirm that a message has not been tampered with and verify the sender’s identity.
200. How does RSA protect against replay attacks in secure communications?
a) By using random nonces or timestamps
b) By encrypting messages twice
c) By increasing the key length
d) By requiring symmetric encryption
✅ Answer: a) By using random nonces or timestamps
🔹 Replay attacks can be prevented by including unique values such as timestamps or nonces in encrypted messages.