1. Consider the group Zp for a prime p with multiplication
multiplication mod p). Show that (p − 1)2 = 1 (mod p)
2. Is the above true for any number (not necessarily prime)?
3. Show that the equation a 2 − 1 = 0, has only two solutions
mod p.
4. Consider (p − 1)!. Show that (p − 1)! = −1 (mod p) Remark:
Think about what are the values of inverses of 1, 2, . . ....
0 mod 35 = 〈0 mod 5, 0 mod 7〉 12 mod 35 = 〈2 mod 5, 5 mod 7〉 24
mod 35 = 〈4 mod 5, 3 mod 7〉
1 mod 35 = 〈1 mod 5, 1 mod 7〉 13 mod 35 = 〈3 mod 5, 6 mod 7〉 25 mod
35 = 〈0 mod 5, 4 mod 7〉
2 mod 35 = 〈2 mod 5, 2 mod 7〉 14 mod 35 = 〈4 mod 5, 0 mod 7〉...
a. Solve 7x + 5 ≡ 3 (mod 19).
b. State and prove the Chinese Remainder Theorem
c. State and prove Euler’s Theorem.
d. What are the last three digits of 9^1203?
e. Identify all of the primitive roots of 19.
f. Explain what a Feistel system is and explain how to decrypt something encoded with a Feistel system. Prove your result.
Which of the following are groups? + And · denote the
usual addition and multiplication of real numbers.
(G, +) with G = {2^ n | n ∈ Z},
(G, ·) with G = {2 ^n | n ∈ Z}.
Determine all subgroups of the following cyclic group
G = {e, a, a^2, a^3, a^4, a^5}.
Which of these subgroups is a normal divisor of G?
Which of the following are groups? + And · denote the
usual addition and multiplication of real numbers.
(G, +) with G = {2 n | n ∈ Z},
(G, ·) with G = {2 n | n ∈ Z}.
Determine all subgroups of the following cyclic group
G = {e, a, a2, a3, a4, a5}.
Which of these subgroups is a normal divisor of G?
Let Z2 [x] be the ring of all polynomials with coefficients in Z2. List the elements of the field Z2 [x]/〈x2+x+1〉, and make an addition and multiplication table for the field. For simplicity, denote the coset f(x)+〈x2+x+1〉 by (f(x)) ̅.