Intro to Cryptography WGU C839 Module 3 Questions and Answers 100% Pass

Intro to Cryptography WGU C839 Module 3 Questions and Answers 100% Pass Consists of public and private keys The public key is made public by publishing to a directory or installed on a computer. The private key is kept secret Does not involve exchanging a secret key or key exchange The public key is used to encrypt messages only the recipients private key can decrypt Asymmetric Cryptography Slower then Symmetric algorithms provides a secure way to communicate provides a method of validation Non-repudiation Disadvantages and Advantages of Asymmetric Crypto Denotes the natural numbers. These are also sometimes called the counting numbers. they are 1, 2, 3, etc. N Denotes the integers. These are whole numbers -1, 0, 1, 2, etc. The natural numbers combined with zero and and the negative numbers Z Denotes the rational number (ratios of integers). Any number that can be expressed as a ratio of two integers. i.e. 3/2, 17/4, 1/5 Q Denotes the real numbers. This includes the rational numbers as well as numbers that cannot be expressed as a ratio of two integers, such as √2 R Denotes imaginary numbers. These are numbers whose square is a negative √-1 - 1i i Having changes to one character in the plaintext affect multiple characters in the ciphertext. Diffusion Attempts to make the relationship between the statistical frequencies of the ciphertext and the actual key as complex as possible. Occurs by using a complex substitution algorithm Confusion A small change that yields large effects on the output. This is a Fiestel variation on Claude Shannon's concept of diffusion. Avalanche In Information Theory this is the measure of the uncertainty associated with a random variable Entropy It is impossible to compress the data such that the code rate is less that the Shannon entropy of the source, without it being virtually certain that information will be lost. Source Coding Theorem Any number whose factors are 1 and itself Prime Numbers If a random number N is selected, the chance of it being a prime is approximately 1 /In(N) where In(N) denotes the natural logarithm of N Prime Number Theorem Method for generating prime numbers Mn - 2n -1 Works for n 2, 3, 5, 7 but failed on n = 11 and many other n values Mersenne Primes A number that has no factors in common with another number 3 and 7 are one of these. Co-Prime Numbers The number of positive integers less than or equal to n that are co-prime to n is called the " " of n. If m and n are co-prime then: Φ(m*n) = φm * φn Φ is the symbol for the Euler phi function Euler's Totient Dividing A by N and returning the remainder. i.e. 5 mod 2 = 1 (5/2, 2 * 2 = 4, 5 - 4 = 1) 12 mod 5 = 2 (12/5, 5 * 2 = 10, 12 - 10 = 2) Sometimes symbolized as %, as in 5 % 2 = 1 Modulus Operator Sequence of numbers derived by adding the last two numbers to create the next. N1 + N2 = n3 First few sequences. 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55 Fibonacci Numbers The number of people you would have to invite to your birthday party so that two will have the same birthday, with high probability. It is approximately 1.174 √365. or 1.174 √N to have a high probability of collision. Birthday Theorem This is an attempt to find a collision for a given hash. If we take MD5 with a 128-bit output, you would have to try 2^128 possible hashes to guarantee a collision which is a very large number. If you use the birthday paradox you would need 1.174√2^128. This is still a large number but magnitudes smaller then 2^128 Birthday Attack A sequence of random numbers with low probability of containing identical consecutive elements K1 A sequence of numbers which is indistinguishable from 'true random' numbers according to specified statistical tests K2 It should be impossible for any attacker to calculate or otherwise guess from any given sub-sequence any previous or future values in the sequence K3 It should be impossible for an attacker to calculate or guess from an inner state of the generator any previous numbers in the sequence or any previous inner generator states K4 Uncorrelated sequences You cannot take a given stretch of numbers and use that to predict subsequent bits. There is literally no correlation between one section of output bits and another. Long Period The series of digits should never have any repeating patterns. The distance between repetitions is this period, the longer the period the better. Traits of a good PRNG This generator is determined by the following four integer values m the modulus m > 0 a the multiplier 0, 0 < a < m c the increment 0, 0 < c < m X0 the starting value 0, 0 < X0 < m The algorithm is: Xn + 1 = (aXn + c)mod m Where n>0 Linear Congruential Generator This algorithm M=pq is the product of two large primes p and q. At each step of the algorithm, some output is derived from Xn + 1. The main difficulty of predicting the output lies in the difficulty of the "quadratic residuosity problem". Put simply, given a composite number n, find whether x is a perfect square modulo n. It is just as difficult to break as RSA pubic-key cryptosystem which involves the factoring of large prime numbers. The format for this algorithm is as follows: Xn+1 = Xn2 Mod M Blum Blum Shub This algorithm is no longer recommended by its inventors. It consists of four parts. An Entropy accumulator A generation mechanism Reseed mechanism Reseed control Yarrow This algorithm is a replacement for Yarrow. It has three main components. A generator, which is seeded and produces pseudo-random data The entropy accumulator, it collects random data and seeds the generator. The seed file, which has initial seed values Fortuna This protocol allows two parties to establish a shared key over an insecure channel. Contains two parameters called p and g Parameters p is a prime number. Parameter g (the generator) is an integer less then p with the following properties For every number n between 1 and p-1 inclusive, there is a power k of g such that n=gk mod p Used for key exchange of symmetric keys Diffie-Hellman The most widely used public key cryptography algorithm in existence and is based on the relationships with prime numbers and how difficult it is to factor a large integer composed of two or more large prime numbers. RSA This is a protocol for key agreement that is based on Diffie-Hellman It is incorporated in the public-key standard IEEE P1363 MQV This algorithm was adopted by the US government in 1993 with FIPS 186 DSA This algorithm bases its security on the fact that finding the discrete logarithm of a random elliptic curve element with respect to a publicly-known base point is difficult to the point of impractical to do. Based on equation of the form y2 = x3 + Ax + B Along side a distinguished point at infinity, denoted. Elliptic Curve This algorithm is used in some PGP implementations as well as GNU Privacy Guard software. Consists of three parts: Key generator Encryption algorithm Decryption algorithm This encryption is probabilistic, Any given plaintext can be encrypted to may possible ciphertexts Elgamal