#KO-01 : Pengenalan Kriptografi

Introduction

Welcome to the tutorial on classical cryptography! In this guide, we will explore the fundamental concepts of cryptography as presented in the introductory video by Doddy Ferdiansyah. This tutorial is designed to help you understand the basics of classical cryptography and its applications, laying the groundwork for further study in this fascinating field.

Step 1: Understanding Cryptography

• Cryptography is the practice of securing information by transforming it into an unreadable format for unauthorized users.
• Its primary goal is to maintain confidentiality, integrity, and authenticity of data.
• Familiarize yourself with key terms:
  • Plaintext: The original message.
  • Ciphertext: The encrypted message.
  • Key: A piece of information that determines the output of the encryption algorithm.

Step 2: Explore Classical Cryptography Techniques

• Classical cryptography includes several well-known techniques:
  • Caesar Cipher: A substitution cipher where each letter is shifted by a fixed number in the alphabet.
    • Example: With a shift of 3, A becomes D, B becomes E, etc.
  • Vigenère Cipher: A method that uses a keyword to dictate the shifts for each letter in the plaintext.
    • To encrypt, repeat the keyword until it matches the length of the plaintext, then apply the Caesar shift for each letter based on the corresponding letter in the keyword.

Step 3: Hands-On Practice with Ciphers

• Try encrypting and decrypting messages using the ciphers mentioned:
  • For the Caesar Cipher:
    1. Choose a plaintext message.
    2. Select a shift value (e.g., 3).
    3. Replace each letter in the plaintext with the letter that is a fixed number of places down the alphabet.
  • For the Vigenère Cipher:
    1. Write down your plaintext and keyword.
    2. Create a table of the alphabet for reference.
    3. Encrypt by determining the shift for each letter based on the keyword.

Step 4: Recognizing the Limitations of Classical Cryptography

• Understand the vulnerabilities:
  • Classical methods are susceptible to frequency analysis, where an attacker studies the frequency of letters or groups of letters in the ciphertext.
• Consider the necessity for more advanced techniques in modern applications.

Conclusion

In this tutorial, we reviewed the basics of classical cryptography, including key concepts and techniques like the Caesar and Vigenère ciphers. To further enhance your knowledge, consider delving into the next modules in the series, which will expand on these foundational elements and introduce more advanced cryptographic methods. Happy learning, and remember to keep your information secure!