Security

Practice and study of secure communications

Functions

Name	Preview	Code	Difficulty
Security Functions	Complete a function that takes input x and return the remainder of x divided by 11.	C++	Easy
Security Functions II	Complete the function that takes x as the input and returns (x*x)	C++	Easy
Security Bijective Functions	You’ll be given an integer n and a function f:X→X where X={1,2,3,…,n}. Determine whether the function is a bijective function or not.	C++	Easy
Security Function Inverses	Find the inverse of a given function f.	C++	Easy
Security Permutations	Given a function f, find f(f(x)) for all x ∈ {1,2,3,…,n}.	C++	Easy
Security Involution	Determine whether function f is an involution or not.	C++	Easy

Terminology and Concepts

Name	Preview	Code	Difficulty
Security - Message Space and Ciphertext Space	Given a message, you need to find what message you obtain if you shift each digit in the message string ( 1 to the right and cyclic).	C++	Easy
Security Key Spaces	Consider a message that consists of decimal digits and a key, e, which operates by shifting each digit by e places. Find the corresponding cipher text.	C++	Easy
Security Encryption Scheme	Count the number of bijections and the number of keys that produce different encryption functions.	C++	Easy

Cryptography

Name	Preview	Code	Difficulty
PRNG Sequence Guessing	Given last ten output values of random.nextInt(), guess the next value to be output by the generator.	C++	Medium
Keyword Transposition Cipher	Given a piece of cipher text and the keyword used to encipher it, write an algorithm to output the original message .	Python	Easy
Basic Cryptanalysis	Given a piece of text encoded with a simple monoalphabetic substitution cipher, use basic cryptanalytic techniques to attempt to recover the original plain text.	Python	Hard