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M1: Introduction to Cryptography

Justin David Pineda CISSP, CISM

Version 1

Sep 2025

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Learning Objectives

  • Define cryptography in simple terms
  • Explain why cryptography is necessary
  • Identify key goals of cryptography
  • Recognize examples of cryptography in everyday technologies

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Motivation Question

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Why Cryptography Matters

  • Protects personal privacy
  • Secures business transactions
  • Enables trust in digital communication
  • Backbone of cybersecurity

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Cryptography in Everyday Life

  • Messaging apps (WhatsApp, Signal)
  • Online shopping (credit cards)
  • Secure browsing (HTTPS)
  • Cloud storage & backups
  • Digital signatures

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Key Security Goals

  • Confidentiality – keep data secret
  • Integrity – prevent unauthorized changes
  • Authentication – verify identities
  • Non-repudiation – prevent denial of actions

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Core Concepts

  • Encryption & Decryption
  • Plaintext & Ciphertext
  • Keys (public, private, symmetric)
  • Algorithms vs. protocols

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A Short History

  • Ancient ciphers (Caesar, Vigenère)
  • WWII Enigma machine
  • 1970s: RSA, DES
  • 21st century: Internet cryptography

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Real World Case Study: WhatsApp

  • 2016: End-to-end encryption (Signal protocol)
  • Protects 2B+ users’ conversations
  • Governments debate lawful interception

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Group Exercise 1

  • Identify 5 technologies you use daily with cryptography
  • Classify by goal: confidentiality, integrity, authentication, non-repudiation
  • Share findings with class

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Group Exercise 2 / Lab

  • Decrypt a short Caesar cipher message
  • Discuss strengths & weaknesses of classical cryptography

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Knowledge Check Q1

  • Which of the following is NOT a goal of cryptography?
  • A. Confidentiality
  • B. Integrity
  • C. Availability
  • D. Authentication

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Knowledge Check Q2

  • Plaintext refers to:
  • A. Encrypted data
  • B. Original readable message
  • C. Randomized key sequence
  • D. Hashed message

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Knowledge Check Q3

  • Which app popularized end-to-end encryption in messaging?
  • A. Facebook Messenger
  • B. WhatsApp
  • C. Instagram
  • D. TikTok

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Knowledge Check Q4

  • Which historical device was cracked in WWII?
  • A. Caesar Cipher
  • B. Enigma Machine
  • C. Atbash Cipher
  • D. Polybius Square

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Knowledge Check Q5

  • Symmetric key cryptography uses:
  • A. One key for encryption only
  • B. Two different keys
  • C. Same key for both encryption and decryption
  • D. No key at all

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Cryptography in Society

  • Debates: Privacy vs. Security
  • Government access vs. individual rights
  • Cryptography as tool for empowerment/conflict

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Further Reading

  • Keith Martin, Everyday Cryptography (Ch. 1–2)
  • Bruce Schneier, Applied Cryptography
  • Articles: End-to-End Encryption, Enigma Story

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Lessons Learned

  • What’s one insight you learned today?
  • How does cryptography affect your daily life?
  • One example you’ll look at differently now?

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Closing

  • Next Week: Classical Cryptography
  • Reminder: Read Ch. 3

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