Cryptography — Test 1

Correct Answer: A. A. Algorithm for performing encryption and decryption
Explanation: Cipher is a method to implement encryption and decryption of messages travelling in a network. It’s used to increase the confidentiality of the messages.

Correct Answer: B. B. Receiver
Explanation: The private key is kept only by the receiver of the message. Its aim is to make sure that only the intended receiver can decipher the message.

Correct Answer: C. C. Electronic code book algorithm
Explanation: Electronic code book algorithm is a block cipher method in which each block of text in an encrypted message corresponds to a block of data. It is not feasible for block sizes smaller than 40 bits.

Correct Answer: A. A. Transpositional ciphers
Explanation: In transposition ciphers, the order of letters in a plaintext message is shuffled using a pre-defined method. Some of such ciphers are Rail fence cipher and Columnar transposition.

Correct Answer: A. A. Block cipher
Explanation: DES is a symmetric key block cipher in which the block size is 64 bits and the key size is 64 bits. It is vulnerable to some attacks and is hence not that popularly used.

Correct Answer: A. A. To find some insecurity in a cryptographic scheme
Explanation: Cryptanalysis is a field of study in which a cryptographic scheme is intentionally tried to breach in order to find flaws and insecurities. It is used to make sure that the scheme is least vulnerable to attacks.

Correct Answer: B. B. Transport layer security (tls)
Explanation: TLS has strong message authentication and key-material generation to prevent eavesdropping, tampering and message forgery. It has been used since the year 1996.

Correct Answer: A. A. A5/2 cipher
Explanation: The A5/2 cipher was published in the year 1996 and was cryptanalysed in the same year within a month. It’s use was discontinued from the year 2006 as it was really weak.

Correct Answer: B. B. Asymmetric key encryption algorithm
Explanation: The ELGamal encryption system was made by Taher Elgamal in the year 1985 and is an asymmetric key algorithm. It is popularly used in PGP and other systems.

Correct Answer: A. A. Fixed size bit string
Explanation: Cryptographic hash functions are used in digital signatures and message authentication codes. The only issue with it is that it returns the same hash value every time for a message making it vulnerable to attackers to evaluate and break the cipher.