Contents: Chapter 1: A History of Cryptography 1 Chapter 2: Large Integer Computing 33 Chapter 3: The Integers 65 Chapter 4: Linear Diophantine Equations and Linear Congruences 89 Chapter 5: Linear Ciphers 105 Chapter 6: Systems of Linear Congruences—Single Modulus 125 Chapter 7: Matrix Ciphers 143 Chapter 8: Systems of Linear Congruences—Multiple Moduli 161 Chapter 9: Quadrati…