Modular Arithmetic

(a mod n) + (b mod n) = (a + b) mod n
(a mod n) * (b mod n) = ab mod n
mod n = b $\leftrightarrow$ ab mod n = 1 (inverse)

Uses identities a^2c mod n = (a^c)² mod nand a^2c+1 mod n = a * (a^c)² mod n.