RSA and AES Encryption Question & Answers July 9, 2025 By WatElectronics This Article lists 100+ RSA and AES Encryption MCQs for engineering students. All the RSA and AES Encryption Questions & Answers given below include a solution and link, wherever possible, to the relevant topic. Both RSA & AES are encryption algorithms with different approaches. RSA is an asymmetric algorithm, with separate keys for encryption & decryption. AES is a symmetric algorithm with a similar key for both processes. So, RSA is slower, used for key exchange & digital signatures, whereas AES is much faster, used for large amounts of data encryption. 1). Who are the inventors of RSA encryption? Rivest, Shamir, Adleman Ron, Sam, Adam Ritchie, Shannon, Anderson Reiman, Saltzer, Abrams None Hint 2). RSA encryption is primarily used for? Symmetric key encryption Data compression Asymmetric key encryption Network routing None Hint 3). What type of mathematical problem is RSA based on? Matrix inversion Elliptic curves Integer factorization Hash collisions None Hint 4). In RSA, which key is publicly shared? Private Key Secret Key Public Key Master Key None Hint 5). What is the typical size of RSA keys used in practice? 64 bits 128 bits 1024 bits or more 256 bits None Hint 6). What does the RSA private key do? Encrypts the data Decrypts the data Multiplies the data Signs SSL certificates only None Hint 7). What are the key components of RSA key generation? Primes, modulus, public/private exponents Elliptic points, fields, hashes Matrices, determinants, rows IP addresses, DNS, routers None Hint 8). Which of the following is not a step in RSA key generation? Choose two large prime numbers Compute Euler's totient Select e such that it is a factor of φ(n) Compute d as the modular inverse of e None Hint 9). What is Euler’s totient function φ(n) for RSA? n + 1 (p + q)/2 (p - 1)(q - 1) pq None Hint 10). What is the purpose of the exponent 'e' in RSA? Used for digital signature Used for decryption Used for computing the modulus Used for encryption None Hint 11). What is the formula for RSA encryption? E = M^d mod n E = M + e mod n C = M^e mod n C = e × M mod n None Hint 12). The RSA decryption formula is: M = C^e mod n M = C^d mod n M = C × e mod n M = e^C mod n None Hint 13). Which condition must be satisfied for choosing 'e'? e must divide φ(n) e must be a prime factor of n gcd(e, φ(n)) = 1 e must be less than both p and q None Hint 14). In RSA, what is ‘d’ typically known as? Encryption key Modulus Public key Private key exponent None Hint 15). What operation ensures RSA decryption works correctly? e × d = n d = e^(-1) mod φ(n) d = p + q d = e + φ(n) None Hint 16). Which programming language provides RSA support in the cryptography or PyCryptolibrary? Java Python HTML SQL None Hint 17). Which standard defines RSA encryption? ISO/IEC 27002 PKCS #1 SHA-256 IEEE 802.11 None Hint 18). What is the role of padding in RSA? Compresses data Fills buffer with zeros Prevents mathematical attacks Encrypts faster None Hint 19). Which attack targets RSA if no padding is used? Brute force Timing attack Chosen ciphertext attack Homomorphic attack None Hint 20). What is the modulus n used for? Signature storage Digital certificate Encryption and decryption bounds Key exchange None Hint 21). What does RSA stand for? Remote Security Algorithm Random Secure Algorithm Rivest–Shamir–Adleman Real-time Secure Access None Hint 22). What’s the smallest recommended RSA key size today? 512 bits 1024 bits 2048 bits 4096 bits None Hint 23). What ensures RSA is a one-way function? Modular arithmetic XOR operation Hardness of factorizing n Fast exponentiation None Hint 24). Which part of RSA is computationally expensive? Encryption Decryption Key generation Hashing None Hint 25). How many keys are generated in RSA? One Two Three Four None Hint 26). What is the digital signature in RSA? Hash of plaintext Message encrypted with public key Hash encrypted with private key Message encrypted twice None Hint 27). Why are primes used in RSA? They are random Easy to compute Compatible with hashing Difficult to factor None Hint 28). What makes decryption fast in practice? RSA has fast decryption Use of small primes Hardware support Chinese Remainder Theorem None Hint 29). What is the value of n in RSA if p = 17 and q = 11? 28 175 187 121 None Hint 30). Which is true about e = 65537? Common value for e Unsafe public exponent Must be less than 10 Used only in decryption None Hint RSA and AES Encryption MCQs for Quiz 31). RSA is vulnerable to which attack without proper padding? Side-channel attack Brute-force attack Man-in-the-middle attack Chosen plaintext attack None Hint 32). What is the main bottleneck in RSA? Encryption speed Key generation time Padding method Hashing None Hint 33). Which of the following uses RSA internally? DNS IP routing HTTPS (TLS/SSL) FTP None Hint 34). Which encryption system is faster than RSA? RSA with larger e RSA with padding ECC AES None Hint 35). Can RSA be used for both encryption and signatures? Yes No Only for signatures Only for encryption None Hint 36). What is modular exponentiation in RSA? e mod M M^e mod n n^e mod M e^n mod M None Hint 37). RSA key is part of which file in SSL? CSR file Certificate file Private key file Log file None Hint 38). Which is safer: 2048-bit RSA or 256-bit ECC? 2048-bit RSA 4096-bit RSA 128-bit ECC 256-bit ECC None Hint 39). In RSA, what does OAEP stand for? Oracle Access Encryption Protocol Optimal Asymmetric Encryption Padding One-time Asymmetric Encoding Process Optimal Algorithm for Encryption Policy None Hint 40). Can RSA be used in block mode like AES? Yes No Only with CBC Only with GCM None Hint 41). What is a real-world use of RSA? Video compression Data storage Email encryption Web hosting None Hint 42). Why is RSA not used for bulk data encryption? Not accurate Lacks integrity Too slow Not scalable None Hint 43). What makes RSA reversible? Symmetric nature Use of modular inverse Use of XOR Hashing None Hint 44). In RSA, what makes brute-force impractical? Use of large keys Random salts Matrix operations Public modulus None Hint 45). Which key do you use to verify an RSA signature? Same private key Another private key Public key Symmetric key None Hint 46). Why is the private key kept secret? To reduce traffic To enable compression It can decrypt data It generates session keys None Hint 47). In RSA, what is meant by ciphertext? Input to hashing Public key Encrypted message Plaintext None Hint 48). What does signing with RSA ensure? Confidentiality Authenticity Compression Decryption None Hint 49). Which cryptographic library supports RSA in Java? OpenSSL Crypto++ Bouncy Castle LibreSSL None Hint 50). Which mathematical tool helps compute 'd' in RSA? Fermat’s Theorem Extended Euclidean Algorithm Taylor Series Lagrange Interpolation None Hint RSA and AES Encryption MCQs for Exams 51). What does AES stand for? Advanced Encryption Scheme Advanced Encryption Standard Algorithmic Encoding Standard Application Encryption System None Hint 52. AES is a type of? Asymmetric encryption Hash function Symmetric encryption Digital signature None Hint 53). What block size does AES operate on? 64 bits 128 bits 256 bits Variable None Hint 54). What are the possible AES key sizes? 64, 128, 256 bits 128, 192, 256 bits 128, 160, 224 bits 64, 96, 128 bits None Hint 55). How many rounds does AES-128 perform? 10 12 14 16 None Hint 56). Who developed the AES algorithm? IBM RSA Security NIST Vincent Rijmen and Joan Daemen None Hint 57). What is Rijndael? A hashing algorithm The algorithm behind AES A cipher mode A type of symmetric block None Hint 58). AES is classified as which kind of cipher? Stream cipher Transposition cipher Block cipher Lattice cipher None Hint 59). Which transformation is not part of AES rounds? SubBytes AddRoundKey ShiftRows Transposition None Hint 60). What is the function of the SubBytes step? Key expansion Bit shuffling Non-linear substitution using S-box Bit rotation None Hint 61). What happens in the ShiftRows step of AES? Rotates columns Swaps rows with keys Cyclically shifts rows Reverses row order None Hint 62). MixColumns in AES ensures? Key expansion Bit masking Diffusion Compression None Hint 63). AddRoundKey is a? Linear transformation Byte-level XOR with the round key Random permutation Swap operation None Hint 64). AES operates on which data structure? Stack Ring 4x4 Byte Matrix (State) Queue None Hint 65). What size is the AES S-box? 8x8 bits 4x4 bits 16x16 bytes 2x2 bytes None Hint 66). Which operation is used in MixColumns? Addition modulo 2 XOR only Matrix multiplication over GF(2⁸) Substitution None Hint 67). AES decryption uses? The same steps as encryption Reverse steps with inverse operations Double encryption No rounds None Hint 68). Which AES key schedule operation is performed? Mixing Hashing RotWord, SubWord, Rcon Permutation None Hint 69). AES uses how many bits for each round key in AES-128? 128 192 256 64 None Hint 70). AES provides which types of security properties? Only confidentiality Confidentiality and authentication Confidentiality, integrity, availability Authentication only None Hint RSA and AES Encryption MCQs for Students 71). Which AES mode is suitable for parallel processing? CBC CFB ECB CTR None Hint 72). AES key expansion outputs how many round keys in AES-128? 9 10 11 12 None Hint 73). ECB mode in AES is insecure because: It is too slow It repeats patterns It uses asymmetric keys It doesn't use XOR None Hint 74). AES was selected by? NSA IEEE NIST W3C None Hint 75). What is the maximum number of rounds in AES? 10 12 14 16 None Hint 76). AES performs well on? Hardware only Software only Both hardware and software Neither None Hint 77). AES S-box is based on? Permutations only Inversion in GF(2⁸) Hashing XOR tables None Hint 78). AES is vulnerable to? Brute force in 1 minute Quantum attacks in future Random bit flipping Arithmetic overflow None Hint 79). Which mode adds an IV to AES? ECB CBC ECB and CTR All modes None Hint 80). What is the IV size in AES-CBC? 64 bits 128 bits 256 bits Variable None Hint 81).Which of the following is a padding scheme used in AES? PSS OAEP PKCS#7 SHA-1 None Hint 82). What does the AES key schedule produce? A single hash Random primes A set of round keys A block cipher mode None Hint 83). Which of these AES modes provides both encryption and authentication? CBC ECB GCM CFB None Hint 84). Which key size in AES offers the highest security? 64 bits 128 bits 192 bits 256 bits None Hint 85). The AES encryption and decryption process is? Identical Similar with inverted operations Completely different Based on hashing None Hint 86). Which AES mode is vulnerable to block replay attacks if IV is reused? CTR ECB CBC GCM None Hint 87). Which part of AES ensures non-linearity? AddRoundKey ShiftRows MixColumns SubBytes None Hint 88). The AES state is modified in how many rounds in AES-256? 10 12 14 16 None Hint 89). The output of AES encryption is? Hash Plaintext Ciphertext Message digest None Hint 90). AES operates on which number of bits per block? 64 128 192 256 None Hint 91). Which programming language provides AES via cryptography or PyCrypto libraries? Java Python HTML C# None Hint Please refer to this link to know more about Cryptography MCQs. 92). Which field is used in AES for all operations? GF(2⁴) GF(2⁸) GF(2¹⁶) Zp None Hint 93). Which AES mode is not a feedback mode? CFB OFB CTR ECB None Hint 94). How many bytes are there in the AES 128-bit key? 8 16 24 32 None Hint 95). Which operation is not used in AES key expansion? RotWord SubWord Rcon MixColumns None Hint 96). AES replaced which earlier encryption standard? RSA 3DES Blowfish RC4 None Hint 97). The AES key size affects which of the following? Cipher block size Rounds in encryption Bit-ordering IV length None Hint 98). In AES, which step is skipped in the final round? SubBytes AddRoundKey ShiftRows MixColumns None Hint 99). AES is a part of which standard for securing Wi-Fi? WEP WPA WPA2 TLS None Hint 100). Which type of cryptanalysis is AES resistant to? Brute-force Differential Linear All of the above None Hint Time's up
