Foundations

Question 1

What is fermats little theorem

Answer 1

a^p = a mod p

a^(p-1) = 1 mod p

Question 2

What is the public key pair for RSA

And what are they

Answer 2

(n, e)

n=pq

e is between 0 and (p-1)(q-1)
It is coprime of (p-1)(q-1)

Question 3

What is the private key for RSA

Answer 3

d

de = 1 mod (p-1)(q-1)

Question 4

How do you encrypt a message M

Answer 4

Encrypted message = M^e mod n

n is larger than M

Question 5

How do you decrypt a message c

Answer 5

M = c^d mod n

Question 6

What’s the difference between combinations and permutations

Answer 6

Permutations care about the order of the set, combinations don’t

Think of it like a permutation padlock

Question 7

What is the equation for possible combinations of K numbers into a set size N if the order matters
(permutation)

Answer 7

n! / (n - k)!

Question 8

What is the equation for picking a set of size n from k values when the order doesn’t matter
(combination)

Answer 8

n! / k!(n - k)!

Question 9

How do you find the expected value of a random variable

Answer 9

For P(X=x)

Sun all the x(probability of x)

E.g 0(0.3) +1(0.25)+2(0.03) etc

Question 10

What is the variance of a random variable

Answer 10

Var(x) = e(x2) - e(x)2

Question 11

How do you find standard deviation of a random variable

Answer 11

Root(var(x))