Q.1 Which of the following is the main purpose of cryptography?
Data storage
Data confidentiality
Data deletion
Data compression
Explanation - Cryptography ensures that sensitive data remains confidential by encrypting it so only authorized parties can read it.
Correct answer is: Data confidentiality
Q.2 What does 'encryption' mean in cryptography?
Converting data into human language
Deleting data permanently
Transforming readable data into unreadable form
Compressing data to save space
Explanation - Encryption changes plaintext into ciphertext so that unauthorized users cannot understand it.
Correct answer is: Transforming readable data into unreadable form
Q.3 Which of the following is a symmetric encryption algorithm?
RSA
AES
ECC
Diffie-Hellman
Explanation - AES is a symmetric encryption algorithm where the same key is used for both encryption and decryption.
Correct answer is: AES
Q.4 In asymmetric encryption, how many keys are used?
1
2
3
4
Explanation - Asymmetric encryption uses a pair of keys: a public key for encryption and a private key for decryption.
Correct answer is: 2
Q.5 What is plaintext?
Encrypted text
Readable text before encryption
Key used in encryption
Digital signature
Explanation - Plaintext refers to original, human-readable data before encryption is applied.
Correct answer is: Readable text before encryption
Q.6 Which algorithm is widely used in public-key cryptography?
AES
RSA
DES
SHA-256
Explanation - RSA is a commonly used public-key (asymmetric) encryption algorithm.
Correct answer is: RSA
Q.7 What is ciphertext?
Text compressed for storage
Text encrypted and unreadable
Readable text before encryption
Key used in decryption
Explanation - Ciphertext is the result of encryption, where plaintext is transformed into unreadable text.
Correct answer is: Text encrypted and unreadable
Q.8 Which cryptographic technique ensures that data has not been altered?
Encryption
Decryption
Hashing
Compression
Explanation - Hashing creates a fixed-length value from data to verify its integrity, ensuring it hasn't been changed.
Correct answer is: Hashing
Q.9 What is the full form of AES?
Advanced Encryption Standard
Automatic Encoding System
Applied Encryption Standard
Advanced Encoding System
Explanation - AES stands for Advanced Encryption Standard, a popular symmetric encryption algorithm.
Correct answer is: Advanced Encryption Standard
Q.10 Which encryption algorithm uses a 56-bit key?
AES
RSA
DES
ECC
Explanation - DES (Data Encryption Standard) uses a 56-bit key, but it is now considered insecure.
Correct answer is: DES
Q.11 What does a digital signature provide?
Confidentiality
Integrity and authentication
Compression
Data deletion
Explanation - Digital signatures verify that data came from the claimed sender and has not been altered.
Correct answer is: Integrity and authentication
Q.12 Which key is kept secret in asymmetric encryption?
Public key
Private key
Session key
Hash key
Explanation - The private key is kept secret and is used for decryption or signing messages.
Correct answer is: Private key
Q.13 What is the process of converting ciphertext back into plaintext called?
Encryption
Hashing
Decryption
Encoding
Explanation - Decryption is the reverse process of encryption, turning ciphertext back into readable plaintext.
Correct answer is: Decryption
Q.14 Which of the following is NOT an encryption algorithm?
AES
RSA
SHA-256
DES
Explanation - SHA-256 is a hashing algorithm, not an encryption algorithm.
Correct answer is: SHA-256
Q.15 In symmetric cryptography, the sender and receiver must:
Use different keys
Share the same key
Use public keys only
Avoid using any key
Explanation - Symmetric cryptography requires both parties to use the same secret key for encryption and decryption.
Correct answer is: Share the same key
Q.16 Which of these is a block cipher?
AES
RSA
SHA-256
ECC
Explanation - AES is a block cipher that encrypts data in fixed-size blocks.
Correct answer is: AES
Q.17 Which cryptographic method is based on mathematical problems like factoring large numbers?
AES
RSA
DES
SHA-1
Explanation - RSA’s security relies on the difficulty of factoring large prime numbers.
Correct answer is: RSA
Q.18 Which of the following is true about hashing?
It can be reversed
It is one-way
It requires keys
It compresses files
Explanation - Hashing is a one-way process; it cannot be reversed to obtain the original data.
Correct answer is: It is one-way
Q.19 What is the size of the output of SHA-256 hashing?
128 bits
256 bits
512 bits
64 bits
Explanation - SHA-256 always produces a fixed 256-bit output regardless of input size.
Correct answer is: 256 bits
Q.20 Which of these is a stream cipher?
AES
DES
RC4
RSA
Explanation - RC4 is a widely known stream cipher, operating on data one bit/byte at a time.
Correct answer is: RC4
Q.21 Elliptic Curve Cryptography (ECC) is considered secure because:
It uses very long keys
It relies on the difficulty of the elliptic curve discrete logarithm problem
It is symmetric
It compresses data
Explanation - ECC’s strength comes from the difficulty of solving elliptic curve discrete logarithm problems.
Correct answer is: It relies on the difficulty of the elliptic curve discrete logarithm problem
Q.22 Which is faster for large data: symmetric or asymmetric encryption?
Symmetric
Asymmetric
Both are equal
Depends on the algorithm
Explanation - Symmetric encryption is much faster than asymmetric encryption for large volumes of data.
Correct answer is: Symmetric
Q.23 Which protocol uses both symmetric and asymmetric encryption?
HTTP
SSL/TLS
FTP
SMTP
Explanation - SSL/TLS uses asymmetric encryption to exchange keys and symmetric encryption for data transmission.
Correct answer is: SSL/TLS
Q.24 What does 'key exchange' mean in cryptography?
Sharing plaintext
Sharing encryption keys securely
Sharing hash values
Deleting old keys
Explanation - Key exchange is the process of securely transmitting encryption keys between communicating parties.
Correct answer is: Sharing encryption keys securely
Q.25 Which of the following is a one-time pad considered to be?
Perfectly secure
Insecure
Block cipher
Stream cipher
Explanation - A one-time pad is theoretically unbreakable when used correctly with random keys.
Correct answer is: Perfectly secure