here's what im learning, for the 1st chapter 
1.1 Divisibility: Division algorithm, Greatest common divisor,
Euclidean algorithm Primes and composite numbers, Fundamental
Theorem of Arithmetic.
1.2 Modular Arithmetic: Congruences, Fermat’s Little Theorem,
Chinese Remainder Theorem, Euler’s φ-function, Euler’s Theorem,
Defnition and properties of F2={0,1}
1.3 Modern Applications: Introduction to cryptography,
Symmetric-key cryptosystems (shift ciphers, affine ciphers), RSA
cryptosystem, Check digits as error detection: e.g., ISBN
