Question

______ uses the concept of pseudo-random sequence.

(a) Stream cipher

(b) DES encryption

(c) Caesar cipher

(d) Block cipher

The question was asked in an interview for job.

My question is based upon Cryptography topic in section Number Theory and Cryptography of Discrete Mathematics

Answer 1

Right option is (a) Stream cipher

Best explanation: The stream cipher is the one-time pad that uses the XOR function on the plaintext with a pseudo-random sequence. The input plaintext is encrypted one byte at a time incrementally. As the random sequence is not possible, a pseudo-random sequence is used. These pseudo-random sequence are the outputs of a generator given an initial seed which is a number used to initialize a pseudo-random number generator.