Consider these 2 functions (all with domain and codomain (Z/pZ)
for some big prime p): h(x) = 1492831*x and h(x) = x3 .
Why are these bad cryptographic hash functions? Give different
reasons for the two.
(A) Let a,b,c∈Z. Prove that if gcd(a,b)=1 and a∣bc, then
a∣c.
(B) Let p ≥ 2. Prove that if 2p−1 is prime, then p
must also be prime.
(Abstract Algebra)
Let p= 11 and 13. (a) Determine all the squares modulo p in
(Z/pZ)∗. (b) Using this determine the value of the Legendre
symbol(a/p)for all a∈(Z/pZ)∗. (c) For all a∈(Z/pZ)∗, compute
a^((p−1)/2) and confirm that a^((p−1)/2)=(a/p).
Let p be an integer other than 0, ±1.
(a) Prove that p is prime if and only if it has the property
that whenever r and s are integers such that p = rs, then either r
= ±1 or s = ±1.
(b) Prove that p is prime if and only if it has the property
that whenever b and c are integers such that p | bc, then either p
| b or p | c.
Let G be a group. For each x ∈ G and a,b ∈ Z+
a) prove that xa+b = xaxb
b) prove that (xa)-1 = x-a
c) establish part a) for arbitrary integers a and b in Z
(positive, negative or zero)
Let p be an odd prime.
(a) (*) Prove that there is a primitive root
modulo p2 . (Hint: Use that if a, b have orders n, m,
with gcd(n, m) = 1, then ab has order nm.)
(b) Prove that for any n, there is a primitive
root modulo pn.
(c) Explicitly find a primitive root modulo
125.
Please do all parts.
Thank you in advance
11.4 Let p be a prime. Let S = ℤ/p - {0} = {[1]p,
[2]p, . . . , [p-1]p}. Prove that for y ≠ 0,
Ly restricts to a bijective map
Ly|s : S → S.
11.5 Prove Fermat's Little Theorem